Subtle changes in the microstructure and dynamics of the triblock copolymer L121, (ethylene oxide)5 (propylene oxide)68 (ethylene oxide)5i.e., E5P68E5, and sodium dodecylsulfate (SDS) system in aqueous medium were investigated using high-resolution nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) and small-angle neutron scattering (SANS) methods. NMR self-diffusion measurements helped us to understand the nature of binding of SDS with L121, and the formation of their mixed aggregates. These results showed that even at low [SDS] (∼2 mM), the addition of L121 stabilized the dynamics of SDS. Furthermore, the increase in [SDS] resulted in progressive changes in the diffusion behavior of both SDS and L121. 13C chemical shift analysis revealed that preferential binding of L121 occurred on the SDS micelle surface. Deuterium (2H) NMR spin-relaxation data evidenced that the formed mixed aggregates were non-spherical in terms of relaxation rate changes, and slowed the dynamics. The rotational correlation times of mixed aggregates were estimated from EPR analysis. A SANS study indicated the presence of uni- and multi-lamellar vesicles of L121 at low [SDS]. The vesicles transformed to mixed L121-SDS micelles in the presence of a higher [SDS]. This was supported by the measurements of 2H NMR spin-relaxation and EPR rotational correlation times.

•A new single molecular multi-analyte probe 1 for the selective detection of Fe3 +, Al3 + and Cr3 + ions is reported.•Fe3 +, Al3 + and Cr3 + form a 1:1 complex with 1, inhibit the PET operating in 1, turn-on the fluorescence.•Competing monovalent, divalent and other trivalent metal cations do not interfere with the detection process.•Probe 1 is membrane permeable, non-lethal and useful for imaging intracellular Fe3 +, Al3 + or Cr3 + levels in live cells.Synthesis and fluorescence turn-on behavior of a naphthalimide based probe is described. Selective interactions of trivalent cations Fe3 +, Al3 + or Cr3 + with probe 1 inhibit the PET operating in the probe, and thereby, permit the detection of these trivalent cations present in aqueous samples and live cells. Failure of other trivalent cations (Eu3 +, Gd3 + and Nb3 +) to inhibit the PET process in 1 demonstrates the role of chelating ring size vis-à-vis ionic radius in the selective recognition of specific metal ions.Through selective interactions, the trivalent cations Fe3 +, Al3 + and Cr3 + turn on fluorescence by inhibiting PET operating in a naphthalimide based probe.

Polymer functionalized surfaces are important components of various sensors, solar cells and molecular electronic devices. In this context, the use of self-assembled monolayer (SAM) formation and subsequent reactions on the surface have attracted a lot of interest due to its stability, reliability and excellent control over orientation of functional groups. The chemical reactions to be employed on a SAM must ensure an effective functional group conversion while the reaction conditions must be mild enough to retain the structural integrity. This synthetic constraint has no universal solution; specific strategies such as “graft from”, “graft to”, “graft through” or “direct” immobilization approaches are employed depending on the nature of the substrate, polymer and its area of applications. We have reviewed current developments in the methodology of immobilization of a polymer in the first part of the article. Special emphasis has been given to the merits and demerits of certain methods. Another issue concerns the utility – demonstrated or perceived – of conjugated or non-conjugated macromolecules anchored on a functionally decorated SAM in the areas of material science and biotechnology. In the last part of the review article, we looked at the collective research efforts towards SAM-based polymer devices and identified major pointers of progress (236 references).

A facile and rapid synthesis of core–shell type magnetite-chitosan microsphere decorated with silver nanoparticles (MCSM) is described. The composition and structure of the as-synthesized microsphere characterized by various spectroscopic and microscopic techniques demonstrated formation of 3.63 ± 0.76 μm MCSM with decoration of silver nanoparticles (AgNPs) having 16 ± 2.5 nm size. The thermogravimetric analysis (TGA) data showed good thermal stability, whereas vibrating sample magnetometry (VSM) analysis indicated the superparamagnetic behavior of the as-synthesized microsphere. The adsorptive removal and antimicrobial property of MCSM was explored for eco-friendly and cost-effective water purification. The MCSM removed 99.99% microbial contaminants and 99.5% of dyes from single as well as multicomponent systems from water bodies efficiently. Furthermore, the dye removal capacity of MCSM (qe = 271.2 ± 14.5 mg/g) was found to be higher compared to the other nanoadsorbents attributing to the high effective surface area of the microsphere and plenty of functional groups of shell structure of chitosan favored binding of dyes on MCSM. Moreover, the adsorbed dyes were desorbed from MCSM at higher pH values and regenerated MCSM was used for next cycle of dye removal. The magnetic behavior of MCSM facilitated easy separation using external magnetic field leading to recycling and reuse, whereas decoration of AgNPs on the microsphere inhibited the bacterial growth. The long-term antibacterial activity of MCSM significantly improved the antifouling property to inhibit the biofilm formation on MCSM. The proposed core–shell type MCSM thus provides a promising opportunity for cost-effective water purification.Keywords: Antibiofouling; Biofilm inhibition; Dye removal; Microsphere; Nanoadsorbent;

The solid and liquid waste management of tanneries has become a serious problem in the leather industry. In this study, we have attempted and succeeded in eliminating these pollutants by a novel method that has not been done anywhere so far. Keratin hydrolysate (KH) from poultry feathers has been utilized along with chrome shavings (CS) for total elimination of the polluting solid and liquid wastes in a tannery. In this process, 100% fixation of the Cr from the chrome exhaust liquor and the dye from the dye exhaust liquor is achieved by the reactions of CS with KH. The infrared spectra of the different stages of CS confirm the fixation of Cr in the chrome shavings–keratin hydrolysate (CSKH) complex. In this work, apart from elimination of tannery pollutants, a leather-like flexible sheet is obtained that can be used in the footwear and leather goods industry. In the scanning electrom microscopy evaluation, the surface morphology of the product exhibits smoothness because of the incorporation of poly(vinyl alcohol) and ethylene glycol. The above findings will open new avenues for further research in solid and liquid waste management of tannery effluents.Keywords: Cost effective; Green environment; Tannery effluents; Value addition

The static 1D 13C and 2D Proton Encoded Local Field (PELF) NMR experiments are carried out in the nematic phase of a less viscous liquid crystal 4-(trans-4′-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT) with a view to find orientational order. The PELF spectra provide better resolution which facilitates the assignment of cyclohexyl and phenyl ring carbons relatively easy. For the cyclohexyl unit, four pairs of dipolar splitting are clearly noticed in contrast to earlier reports on structurally similar mesogens where only two pairs of doublets are seen. The linear relationship between anisotropic chemical shifts and orientational order is established and semi-empirical parameters are obtained to aid the study of the order behaviour of 6CHBT over the entire nematic range. The data further fitted to the Haller equation and a reasonably good agreement is observed. The temperature dependence trends of orientational order parameters extracted for various carbons using 13C–1H dipolar couplings with those of 13C chemical shifts are compared. A gradual decrease in the order parameter is noticed for different molecular segments while traversing from the core to the aliphatic chain via the cyclohexyl ring. The notable decreasing trends of order parameters along the chain are observed similar to those of the corresponding phenyl cyclohexanes reported earlier.

Novel bio-renewable castor oil based polyurethane (PU)–silica nanocomposite films were prepared using castor oil, 1,6-hexamethylene diisocyanate and dibutyltin dilaurate in tetrahydrofuran at room temperature. ATR-FTIR spectra confirm the formation of polyurethane and the presence of silica nanoparticles in the polyurethane matrix. The increase of Si nanoparticle content shifts the peak position of N–H and CO (both hydrogen and non-hydrogen bonded) groups present in the polyurethane structure. Furthermore, Raman spectra confirmed the urethane–amide interaction present in the polyurethane–silica nanocomposites. 29Si CP/MAS NMR spectra evidence the formation and the presence of completely condensed SiO2 species in the polyurethane nanocomposite films. The incorporation of silica nanoparticles increases the thermal stability of the above-mentioned polyurethane films, which can be seen from the increase in activation energy (Ea) values of the degradation process. The Ea values at two stages (Tmax1 and Tmax2) of the degradation process are 133, 139 and 157, 166 kJ mol−1 for PU control and PU-5AMS (5 wt% amine modified silica nanoparticles), respectively. DSC results prove the interfacial interaction present between silica nanoparticles and the polyurethane hard segment, which decreases the melting temperature. Optical transmittance of the polyurethane films decreased with increasing silica content due to the scattering at the interfaces between the silica nanoparticles and polyurethane. It is interesting to note that the presence of silica nanoparticles gives reinforcement to polyurethane film, thereby increasing the storage modulus up to 24% for PU-5AMS. FE-SEM and HR-TEM images confirm the presence of silica nanoparticles in the polyurethane matrix.

The present investigation attempts at fabricating collagen-based scaffolds impregnated with sago starch capped silver nanoparticles (AgNPs), useful for biomedical applications, and aims at studying their physicochemical aspects. AgNPs synthesized through a chemical reduction method, capped using different concentrations of sago starch, are incorporated into collagen derived from fish scales, and lyophilized to form scaffolds. FT-IR spectra confirm and validate the interaction of sago starch capped AgNPs with collagen in the scaffolds. TGA and DSC results indicate enhanced thermal stability of collagen scaffolds impregnated with sago capped AgNPs compared to collagen alone. All the collagen scaffolds containing sago starch capped AgNPs show high tensile strength values for their use as wound dressing materials. Moreover, lower minimum inhibitory concentration values are obtained for the above capped AgNP collagen scaffolds, which indicate higher antibacterial activities compared to uncapped AgNPs tested against both gram positive and negative bacterial strains. The novelty is that the developed scaffolds are biodegradable and in vitro studies reveal them as biocompatible and suitable for tissue regeneration applications.

Peptide based self-assembled structures, especially those from smaller peptides, have attracted much research interest due to their potential applications as biomaterials. These structures have been produced using different solvents (one of the methods), including alcohols, except fluorinated alcohols, which are believed to support non-aggregated structures. Herein, we have studied the ability of 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) solvents to induce self-assembly of an aromatic dipeptide, namely Tyr–Phe (YF). SEM images showed that HFIP and TFE can induce self-assembly with completely different morphologies, namely microribbons and microspheres, respectively, when YF is dried on a glass surface. Optical microscopic images showed that the microribbons possess birefringence under polarized light, whereas the microspheres do not, indicating that the self-assembled structures derived from HFIP solution are more highly ordered and crystalline in nature than those derived from TFE. Spectroscopic results indicated that the YF peptide adopts completely different conformations in these solvents. Time-dependent experiments suggested that the conformation of YF in HFIP is kinetically unstable and undergoes conformational change, whereas it is more stable in TFE, demonstrating that the modes of interaction of the TFE and HFIP solvents with the peptide are dissimilar. Different self-assembled structures were observed at different time intervals when YF was incubated in neat HFIP and 10% HFIP–90% TFE, establishing that the monomeric conformation plays a dominant role in deciding the final self-assembled structure (morphology) of YF. The current results demonstrate that TFE and HFIP solvents can produce self-assembled structures with different morphologies during solvent evaporation, despite their similar properties, such as secondary structural (α-helix) induction and preserving the peptide in its monomeric conformation in solution.

Polymer nanocomposites are developed, for the first time, as transparent films by the covalent addition of polyurethane (PU) prepolymers to trace amounts of functionalized carbon nanotubes, [OH]n–SWCNTs, via an efficient route using mild reagents. These PU nanocomposites, which were uniformly distributed with SWCNTs via covalent bonding between SWCNTs and the polyurethane network show enhanced mechanical, thermal and conductivity (10−4 S cm−1) properties.

Aggregation induced enhanced emission (AIEE) is considered as an important tool to circumvent the aggregation caused quenching (ACQ) effect in organic light emitting diodes (OLEDs). Charge trapping and surplus long wavelength electroluminescence is a cause of concern in single polymer based white OLEDs. However, the potential of luminogens with AIEE property as a credible tool to offset the above problems in white light emitting single polymer is not properly explored. In this study design, synthesis and spectral characterization of a polymerizable luminogen, (2Z,2′Z)-6,6′-(2,7-dibromo-9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl)bis(2-cyano-3-(10-hexyl-10H-phenothiazin-3-yl)acrylate(FCPA) with AIEE property and its copolymers is presented. Lippert-Mataga studies showed that reduced local polarity caused by aliphatic chains in condensed state of FCPA resulted in AIEE property. The copolymers P(FCPA-1) and P(FCPA-0.5) with 1% and 0.5% FCPA moieties showed white electroluminescence and enhanced thin film photoluminescence that matched very closely. The superior performance of OLEDs is attributed to the presence of a phenothiazine group in FCPA that resulted in nearly equal electron and hole injection barriers.

The sidewall functionalization of single-walled carbon nanotubes (SWCNTs) was established by poly (methyl methacrylate) (PMMA) using controlled radical polymerization (CRP) method. A bromide functionalized SWCNT (SWCNT-Br) has been used as an initiator for the synthesis of SWCNT-graft-PMMA (SWCNT-g-PMMA). The efficiency of the sacrificial initiator (S) was monitored during the polymerization process. The obtained polymers possess a uniform distribution of molecular weight with a lower polydispersity index of 1.36. The SWCNTs-based initiator acts as an efficient medium for the controlled growth of polymer on the SWCNTs surfaces. The presence of bimodal gel permeation chromatographic (GPC) curve for the SWCNT-g-PMMA(S) obtained through sacrificial initiator (S) confirms uncontrolled behavior. However, the clear sharp peak for SWCNT-g-PMMA obtained without sacrificial initiator shows its well-controlled process of polymerization, which acts as a mimic to bone cement. The efficiency of the functionalization of SWCNT and the controlled formation of SWCNT-g-PMMA composites were characterized by TGA, Raman, TEM, NMR, XPS and dispersion measurements.

Increasing demand of noble-metal nanoparticles (MNPs) in catalysis research urges the development of a nontoxic, clean, and environmentally friendly methodology for the production of MNPs on solid surface. Herein we have developed a facile approach for biosynthesis of MNPs (Pd, Pt, and Ag) on the surface of Rhizopous oryzae mycelia through in situ reduction process without using any toxic chemicals. The size and shape of the biosynthesized MNPs varied among the MNPs, and “flower”-like branched nanoparticles were obtained in case of Pd and Pt, while Ag produced spheroidal nanoparticles. The cell-surface proteins of the mycelia acted as protecting, reducing, and shape-directing agent to control the size and shape of the synthesized MNPs. Proteins of 78, 62, and 55 kDa were bound on the MNPs surfaces and played a significant role in determining the morphology of the MNPs. The catalytic efficiency varied among the MNPs, and Pd nanoflower exhibited superior catalytic activities in both hydrogenation and Suzuki coupling reactions. Surface composition, concentration, and intracellular localization of MNPs determine the catalytic activity of the biosynthesized MNPs. The nanocatalyst could be easily separated and reused multiple times without significant loss in activity (95% average conversion). Overall, the understanding of this complex biomineralization mechanism and catalytic behavior at the nano–bio interface has provided an alternative for the synthesis of supported metal nanocatalyst to improve the environmental sustainability.

With increasing application of silver nanoparticles (AgNPs) in biological sensing, detection, enzyme immunoassays, and antimicrobial activity as well as SERS, it has been realized that the toxicity limits their application in biomedicine. However, the interaction of proteins with nanoparticle (NPs) surface possessing different chemical functionalities reduces the potential impact of NPs rendering them biocompatible. Here, we have functionalized the AgNPs with β-hydroxy propyl cyclodextrin (β-HPCD-AgNPs) and studied the conformational changes and thermal stability of hemoglobin (Hb) upon interaction with β-HPCD-AgNPs. Interaction of Hb with borohydride-capped AgNPs (BH4-AgNPs) was also evaluated. Hb remained in native form upon binding with β-HPCD-AgNPs which is unveiled by UV–vis and fluorescence spectroscopic as well as dynamic light scattering (DLS) studies. However, BH4-AgNPs induced unfolding of Hb and reduced the α-helical content following interaction with Hb. Further, the accessibility of tryptophan fluorescence was found to be 33% for β-HPCD-AgNPs quencher, which implies that β-HPCD-AgNPs retains the native conformation of Hb Dichroic study revealed that β-HPCD-AgNPs did not affect thermal stability of Hb, whereas BH4-AgNPs decreased the thermal stability of Hb by 5 °C. Hemolysis assay demonstrated the biocompatibility of β-HPCD-AgNPs toward RBC. Functionalization of NPs with controlled surface property thus dictated overall biological reactivity of Hb-AgNPs. Therefore, we trust that the obtained results will help us in designing surface-functionalized AgNPs for biomedical applications.

•Gallic acid (GA) with addition of EDC/NHS improves the thermo-mechanical properties.•GA has accelerated the staggered alignment of collagen fibril.•Improved biocompatibility and cell adhesion properties•GA has the lowest binding energy with collagen like peptide (CLP).•Inaccessible and resistance to collagenase activityThe effect of Gallic acid (GA) in the presence of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC)/N-hydroxysuccinimide (NHS) on collagen scaffold is investigated. The thermal mechanical analyzer (TMA), differential scanning calorimetric (DSC), and thermogravimetric analysis (TGA) including tensile strength (TS, 180 ± 3 MPa), denaturation temperature (Td, 80.03 °C), % elongation (% E, 180 ± 9) and weight loss (31.76%), indicate that the modification improves the structural integrity and stability of the collagen scaffold. The GA–EDC/NHS treatment inhibits the action of collagenase against collagen degradation compared to GA and EDC/NHS. It is concluded from docking studies that GA binds with collagen like peptide (CLP) and collagenase through multiple H-bonds and hydrophobic interactions leading to low binding energy − 5.1 and − 5.3 Kcal/mol, respectively. The hydrophobic core of the GA molecules, probably incorporates itself into the hydrophobic areas of the collagen groups, whereas OH and COOH moieties of GA establish multiple H-bonds with neighboring collagen molecules and carboxamide bond, thereby improving the swelling and water uptake properties, biocompatibility and cell adhesion properties. This results in improving stability of the scaffold, which prevents the free access of the collagenase to reactive sites in the triple helical collagen chains.

•Resveratrol acts as a reducing agent in the synthesis of gold nanoparticles.•Capping of gold nanoparticles by resveratrol prevents self-agglomeration.•Resveratrol capping permits loading of doxorubicin onto gold nanoparticles.•Doxorubicin loaded gold nanoparticles show enhanced anticancer activity in vitro.The green synthesis of gold nanoparticles was achieved by exploiting the antioxidant property of resveratrol (R). The formation of resveratrol stabilized gold nanoparticles (R-GNPs) was confirmed by the observation of the surface plasmon resonance band at 537 nm. The average size of R-GNPs produced in resveratrol medium was ∼35 nm. The geometrical shape and zeta potential of the gold nanoparticles were spherical and −21.2 mV, respectively. R-GNPs showed excellent stability in saline and other buffers mimicking the physiological pH. The MTT assay using fibroblast cells from explants tissue revealed the biocompatibility of R-GNPs. The cytotoxic activity of doxorubicin loaded R-GNPs against glioma carcinoma cell line (LN 229), showed the suitability of R-GNPs as a carrier for anticancer drugs.

A nano-silica–AgNPs composite material is proposed as a novel antifouling adsorbent for cost-effective and ecofriendly water purification. Fabrication of well-dispersed AgNPs on the nano-silica surface, designated as NSAgNP, has been achieved through protein mediated reduction of silver ions at ambient temperature for development of sustainable nanotechnology. The coated proteins on AgNPs led to the formation of stable NSAgNP and protected the AgNPs from oxidation and other ions commonly present in water. The NSAgNP exhibited excellent dye adsorption capacity both in single and multicomponent systems, and demonstrated satisfactory tolerance against variations in pH and dye concentration. The adsorption mainly occurred through electrostatic interaction, though π–π interaction and pore diffusion also contributed to the process. Moreover, the NSAgNP showed long-term antibacterial activity against both planktonic cells and biofilms of Gram-negative Escherichia coli and Pseudomonas aeruginosa. The antibacterial activity of AgNPs retarded the initial attachment of bacteria on NSAgNP and thus significantly improved the antifouling properties of the nanomaterial, which further inhibited biofilm formation. Scanning electron and fluorescence microscopic studies revealed that cell death occurred due to irreversible damage of the cell membrane upon electrostatic interaction of positively charged NSAgNP with the negatively charged bacterial cell membrane. The high adsorption capacity, reusability, good tolerance, removal of multicomponent dyes and E. coli from the simulated contaminated water and antifouling properties of NSAgNP will provide new opportunities to develop cost-effective and ecofriendly water purification processes.

A highly selective and efficient single molecular FRET based sensor has been developed for the ratiometric detection of Fe3+ in aqueous samples and live cells.

Incorporation of the triazolyl moiety modulates the basicity and effective size of the chelating ring, changes the stoichiometry in complex formation and thereby imparts Cu2+ ion selectivity.

Two new rhodamine–indole conjugates 1 and 2 were synthesized for studying their ability to probe specific metal ions at physiological pH in the presence of other competing metal ions. In non-aqueous medium, probe 1 predominantly binds Cu2+ ions with considerable interference from Fe3+ and Ni2+ ions. However, in aqueous medium, 1 exhibits a higher degree of selectivity for Cu2+ ions with little interference from Fe3+ ions, and no interference from Ni2+ ions. The probe 2, obtained by tethering a triazole moiety with probe 1, selectively binds Cu2+ ions in aqueous medium even in the presence of other metal ions including Fe3+ ions. The sensitivity of probe 2 to pH variation and interaction with various amino acids were also investigated. The excellent stability of 2 in physiological pH conditions, non-toxicity, non-interference of amino acids in the detection process, and the remarkable selectivity for Cu2+ ions in aqueous medium allowed the use of 2 in the imaging of live fibroblast cells treated with Cu2+.

The influence of water-insoluble nonionic triblock copolymer PEO–PPO–PEO [poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide)] i.e., E6P39E6 with molecular weight 2800, on the microstructure and self-aggregation dynamics of anionic surfactant sodium dodecylsulfate (SDS) in aqueous solution (D2O) were investigated using high resolution nuclear magnetic resonance (NMR) and small-angle neutron scattering (SANS) measurements. Variable concentration and temperature proton (1H), carbon (13C) NMR chemical shifts, 1H self-diffusion coefficients, 1H spin–lattice and spin–spin relaxation rates data indicate that the higher hydrophobic nature of copolymer significantly influenced aggregation characteristics of SDS. The salient features of the NMR investigations include (i) the onset of mixed micelles at lower SDS concentrations (<3 mM) relative to the copolymer-free case and their evolution into SDS free micelles at higher SDS concentrations (∼30 mM), (ii) disintegration of copolymer–SDS mixed aggregate at moderate SDS concentrations (∼10 mM) and still binding of a copolymer with SDS and (iii) preferential localization of the copolymer occurred at the SDS micelle surface. SANS investigations indicate prolate ellipsoidal shaped mixed aggregates with an increase in SDS aggregation number, while a contrasting behavior in the copolymer aggregation is observed. The aggregation features of SDS and the copolymer, the sizes of mixed aggregates and the degree of counterion dissociation (α) extracted from SANS data analysis corroborate reasonably well with those of 1H NMR self-diffusion and sodium (23Na) spin–lattice relaxation data.

A green synthetic approach for the preparation of silver nanoparticles (AgNPs) in aqueous alkaline medium using cyclodextrin (CD) derivatives as reducer and stabliser is reported. The CD-AgNPs are characterised using UV-visible (UV), FT-IR, mass spectroscopic and cyclic voltammetric (CV) techniques. The difference in morphology is observed with respect to the CD derivatives by transmission electron microscopy and the formation mechanism of AgNPs is discussed. CD-AgNPs display remarkably strong blue emission at 478 and 540 nm upon excitation at 400 nm. The monodispersed and self-assembled AgNPs capped by β-hydroxypropyl cyclodextrin (β-HPCD) show photoluminescence enhancement in the presence of Hg(II), but it is strongly quenched by Al(III). β-HPCD-AgNPs possess good selectivity and sensitivity for the determination of Hg(II) and Al(III) in the concentration range of 20–200 μM. Furthermore, the as-prepared AgNPs serve as an effective catalyst to activate the reduction of p-nitrophenol in the presence of sodium borohydride, which shows comparable catalytic activity. The homogeneous and heterogeneous catalytic activities of CD-AgNPs are assessed using UV and CV techniques, respectively.

A series of castor oil based polyurethane/siloxane cross-linked films were prepared using castor oil, isophorone diisocyanate, and 3-aminopropyl trimethoxysilane by the sol–gel process. Fourier transform infrared (FT-IR) spectra reveal the cross-linking interaction between polyurethane and siloxane moieties, thereby shifting the peak position of characteristic N—H and C═O groups to higher wavenumber. 29Si (silica) solid state nuclear magnetic resonance spectra were used to prove the formation of siloxane network linkage in the polyurethane system, thereby analyzing the Si environment present in the polyurethane/siloxane cross-linked films. The activation energy values at two stages (Tmax1 and Tmax2) for the degradation of polyurethane films were increased with increasing silane ratio. The calculated activation energy values for the higher silane ratio (1.5) are 136 and 170 kJ/mol at Tmax1 and Tmax2, respectively. From contact angle measurements, we observed that increasing siloxane cross-linking increased the hydrophobicity of the films. The optical transmittance obtained from ultraviolet–visible spectra indicated that the film samples are transparent in the region 300–800 nm. The moisture sorption/desorption isotherm curve shows a characteristic behavior of type III isotherm corresponds to hydrophobic materials. Dynamic mechanical studies show that the increase in storage modulus reveals siloxane cross-linking gives rigidity to the films. Atomic force microscopic images show that the introduction of siloxane changes the surface roughness of the polyurethane films. It is found that the siloxane cross-linking can be used to obtain hydrophobic surface films having good thermal stability and optical transmittance.

The metabolic effectiveness of choline lactate in the growth media was investigated relative to conventional carbon source for growing Staphylococcus lentus, a bacterial strain commonly used in bioremediation of industrial effluents and xenobiotic detoxification. Bacterial growth thermodynamics was determined by biocalorimetry. 13C NMR and FTIR spectroscopic analyses traced the consumption of choline lactate at specific time intervals of bacterial growth. Under aerobic conditions, it is apparent that S. lentus initially metabolized lactate for its energy needs, while the choline cation of the ionic salt seemed to provide its C and N for biosynthetic intermediates for cell structure/function, in the growing bacterial colony. Urea accumulation after 40 h of bacterial growth was recorded. Possible metabolic trajectory of choline lactate consumed during S. lentus growth is suggested here. The theoretical estimation of heats of reaction for the proposed metabolic pathway (455 kJ/mol) was comparable with the experimentally obtained reaction enthalpy (435 kJ/mol), which further validated the proposed metabolic pathway. The biomass and energy profile of bacteria growth in choline media was found to be more favorable than in glucose media. The ionic liquid, choline lactate, offers a metabolically and energetically efficient carbon (and nitrogen) source for growing S. lentus.

Bacillus badius isolated from soil has been identified as potential producer of penicillin G acylase (PGA). In the present study, batch experiments performed at optimized inoculum size, temperature, pH, and agitation yielded a maximum PGA of 9.5 U/ml in shake flask. The experiments conducted in bioreactor with different oxygen flow rates revealed that 0.66 vvm oxygen flow rate could be sufficient for the maximum PGA activity of 12.7 U/ml. From a detailed investigation on the strategies of the addition of phenyl acetic acid (PAA) for increasing the production of PGA, it was found that the controlled addition of 10 ml of 0.1 % (w/v) PAA once in every 2 h from 6th hour of growth showed the maximum PGA activity of 32 U/ml. Thus, our studies for the first time showed that at concentration above 0.1 % (w/v) PAA, the PGA production decreased. This selective condition paves the way for less costly bioprocess for the production of PGA.

In the present investigation, we report the thermodynamics of clouding in four amphiphilic drugs viz., two tricyclic antidepressants: amitriptyline hydrochloride (AMT) and imipramine hydrochloride (IMP) and two phenothiazines: chlorpromazine hydrochloride (CPZ) and promethazine hydrochloride (PMT) in the absence and presence of sugars. For an amphiphile, cloud point (CP) can be considered as the limit of its solubility as the phase separates at temperatures above the CP. The clouding components release their solvated water and separate out from the solution. For all the cases, the standard Gibbs energy change of solubilization (ΔGs0) is evaluated, and found to be positive. However, the standard enthalpy change of solubilization (ΔHs0), and the product of standard entropy change of solubilization and temperature (TΔSs0) values are found negative as well as positive.Graphical abstractHighlights► Thermodynamics of amphiphilic drugs, AMT, IMP, CPZ & PMT at CP with/without sugars. ► The ΔGs0 is evaluated, and found to be positive (for all the cases). ► The ΔHs0 and TΔSs0 values are found negative as well as positive. ► The results have relevance in drug delivery/model drug delivery.

“Click” polymerization reaction has been performed on the functional self-assembled monolayer to incorporate polytriazoles. Ellipsometric and atomic force microscopic studies indicated a high degree of polymerization and fairly dense surface coverage. Band gap calculation revealed the possibility of its use as a semiconducting material.

Industrial wastewaters such as tannery and textile processing effluents are often characterized by a high content of dissolved organic dyes, resulting in large values of chemical and biological oxygen demand (COD and BOD) in the aquatic systems into which they are discharged. Such wastewater streams are of rapidly growing concern as a major environmental issue in developing countries. Hence there is a need to mitigate this challenge by effective approaches to degrade dye-contaminated wastewater. In this study, several choline-based salts originally developed for use as biocompatible hydrated ionic liquids (i.e., choline sacchrinate (CS), choline dihydrogen phosphate (CDP), choline lactate (CL), and choline tartarate (CT)) have been successfully employed as the cosubstrate with S. lentus in the biodegradation of an azo dye in aqueous solution. We also demonstrate that the azo dye has been degraded to less toxic components coupled with low biomass formation.

Two new rhodamine based probes 1 and 2 for the detection of Fe3+ were synthesized and their selectivity towards Fe3+ ions in the presence of other competitive metal ions tested. The probe 1 formed a coloured complex with Fe3+ as well as Cu2+ ions and revealed the lack of adequate number of coordination sites for selective complexation with Fe3+. Incorporation of a triazole unit to the chelating moiety of 1 resulted in the probe 2, that displayed Fe3+ selective complex formation even in the presence of other competitive metal ions like Li+, Na+, K+, Cu2+, Mg2+, Ca2+, Sr2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+, Cd2+, Hg2+ and Pb2+. The observed limit of detection of Fe3+ ions (5 × 10−8 M) confirmed the very high sensitivity of 2. The excellent stability of 2 in physiological pH conditions, non-interference of amino acids, blood serum and bovine serum albumin (BSA) in the detection process, and the remarkable selectivity for Fe3+ ions permitted the use of 2 in the imaging of live fibroblast cells treated with Fe3+ ions.

The accelerating rate calorimetry studies on the tributyl phosphate and nitric acid reactions at various acid concentrations revealed that the conditions for red oil formation may vary with acid strength. The accelerating rate calorimeter studies supplemented with FT-IR characterization of the end products confirmed the formation of red oil at temperatures as low as 75 °C. This study thus strongly advocates for a revisit of safety limits set in the fuel reprocessing plants to prevent red oil formation. The chemical pathway for red oil formation is worked out.

A novel voltammetric protein assay has been demonstrated using bovine serum albumin in the presence of silver nanostructures (AgNs) formed electrochemically on gold substrates modified by self-assembled monolayer of thioctic acid. It is shown that the prepared AgNs exhibit voltammetric response characteristic of Ag and shows near Nernstian response at physiological pH. The advantages of the electrochemical assay compared to conventional protein analysis are the wide linear concentration range (10−4–10−11 g/mL) and trace level detection limits (50 pg/mL). The result of this electrochemical analysis agreed well with an independent spectrophotometric method using Bradford reagent, but the detection limit is far superior using the electrochemical method. Further, the modified electrode exhibits high sensitivity and long term stability. We invoke a new concept of surface enhanced activity of Ag+ ions at the electrochemical interface by the negatively charged bovine serum molecules.Graphical abstractHighlights► Formation of silver nanostructure by galvanic replacement method. ► Voltammetric assay of proteins with wide concentration range 10−4–10−11 g/mL. ► Detection of proteins at trace levels (50 pg/mL). ► Surface enhanced activity of silver nanostructure at electrochemical interface. ► Comparison of voltammetric assay with Bradford method.

In the present work, we report the surface properties and mixed micellization of a tricyclic antidepressant drug amitriptyline hydrochloride (AMT) with nonionic surfactant poly(ethylene glycol) t-octylphenyl ether (TX-100) using surface tension measurements. The surface properties in aqueous solution of AMT drug in the absence and presence of TX-100 are presented. The critical micelle concentration (cmc), maximum surface excess concentration at the air/water interface (Γmax) and the minimum area per surfactant molecule at the air/water interface (Amin) parameters are evaluated. Γmax increases and cmc as well as Amin decrease with increasing concentration (mole fraction) of the additive (TX-100). We also report the thermodynamics of AMT in the absence and presence of TX-100 and evaluated Gibbs energies (viz., at air/water interface (Gmin(s)), the standard Gibbs energy change of micellization (ΔmicG0), the standard Gibbs energy change of adsorption (ΔadsG0), the excess free energy change of micellization (ΔGexm)).Variation of the standard Gibbs energy change of micellization, ΔmicG0 and the standard Gibbs free energy change of adsorption, ΔadsG0 of the amphiphilic drug at different concentration/molefraction of TX-100 at 298.15 K.Highlights► Surface properties and mixed micellization studies of drug AMT with surfactant TX-100 using surface tension measurements. ► The cmc of AMT with or without TX-100 were measured and the Γmax and the Amin parameters were evaluated. ► Γmax increases and cmc as well as Amin decrease with increasing concentration of TX-100. ► The thermodynamic parameters of AMT with or without TX-100 were evaluated. ► Gibbs energies (viz., Gmin(s), ΔmicG0, ΔadsG0, ΔGexm) were evaluated and found mixed systems are more stable.

The effects of aeration and agitation on metabolic heat, alkaline protease production and morphology for Aspergillus tamarii MTCC5152 are reported in this manuscript. Measurement of metabolic heat has been attempted by the continuous and dynamic heat balance method in a biological real-time reaction calorimeter. At lower agitation intensities, growth-related processes were dominating. As a result the protease activity and the product heat yields were lower than those for 350 and 450 rpm. Although biomass growth was necessary to obtain maximum protease yield, agitation seemed to play a vital role in the protease production process. Energy dissipation per circulation function of the process is also deduced from power input. At optimal conditions, 350 rpm and 1 vvm, the gassed power required was 0.133 W. Pellet morphology and protease production were studied under different aeration and agitation intensities of A. tamarii. Pellet structure was considerably influenced by DO, a higher DO level resulted in denser pellets (1,018.4 kg/m3) leading to higher protease activity. Coupling of hydrodynamics and bio-reaction highlighted the complex relationship between energy dissipation, substrate uptake rate and fungal physiology. This study emphasised the potential of biocalorimetry as a reliable monitoring and robust control tool for aerobic fermentation of A. tamarii, using agricultural by-products.

Mixed aquo-organic solvents are used in chemical, industrial, and pharmaceutical processes along with amphiphilic materials. Their fundamental studies with reference to bulk and interfacial phenomena are thus considered to be important, but such detailed studies are limited. In this work, the interfacial adsorption of sodium dodecylsulfate (SDS, C12H25SO4–Na+) in dioxane–water (Dn–W) and methanol–water (Ml–W) media in extensive mixing ratios along with its bulk behavior have been investigated. The solvent-composition-dependent properties have been identified, and their quantifications have been attempted. The SDS micellization has been assessed in terms of different solvent parameters, and the possible formation of an ion pair and triple ion of the colloidal electrolyte, C12H25SO4–Na+ in the Dn–W medium has been correlated and quantified. In the Ml–W medium at a high volume percent of Ml, the SDS amphiphile formed special associated species instead of ion association. The formation of self-assembly and the energetics of SDS in the mixed solvent media have been determined and assessed using conductometry, calorimetry, tensiometry, viscometry, NMR, and DLS methods. The detailed study undertaken herein with respect to the behavior of SDS in the mixed aquo-organic solvent media (Dn–W and Ml–W) is a new kind of endeavor.

Fungal cultivation in a biological real-time reaction calorimeter (BioRTCal) is arduous due to the heterogeneous nature of the system and difficulty in optimizing the process variables. The aim of this investigation is to monitor the growth of fungi Aspergillus tamarii MTCC 5152 in a calorimeter. Experiments carried out with a spore concentration of 105 spores/mL indicate that the growth based on biomass and heat generation profiles was comparable to those obtained hitherto. Heat yield due to biomass growth, substrate uptake, and oxygen uptake rate was estimated from calorimetric experiments. The results would be useful in fermenter design and scale-up. Heat of combustion of fungal biomass was determined experimentally and compared to the four models reported so far. The substrate concentration had significant effects on pellet formation with variation in pellet porosity and apparent density. Metabolic heat generation is an online process variable portraying the instantaneous activity of monitoring fungal growth and BioRTCal is employed to measure the exothermic heat in a noninvasive way.

In the present study, we report the micellization and clouding behavior of an amphiphilic antidepressant drug viz., amitriptyline hydrochloride (AMT) at different fixed temperatures and KCl concentrations in aqueous solutions. The critical micelle concentration (cmc) of AMT, as measured by conductivity method, increases with increasing temperature and decreasing with KCl concentration. The thermodynamic parameters viz., standard Gibbs energy (ΔGm0), standard enthalpy (ΔHm0), and standard entropy (ΔSm0) of micellization of AMT are evaluated. The values clearly indicate more stability of the AMT solution in presence of KCl. Like surfactant, AMT also shows phase separation behavior. The cloud point (CP) of AMT in water decreases with increase in pH of the medium because of the deprotonation of the drug molecule. The CP values increase with increasing KCl concentration and AMT concentrations, clearly indicating the micellar growth at higher concentration. Furthermore, for better understanding of the behavior of drug molecule in water, we evaluated various thermodynamic parameters of the above drug molecule at CP.Graphical abstractPlots (representative) of specific conductance vs. [AMT] in absence and presence of different fixed KCl concentrations at 303.15 K. The curves 2, 3, 4, and 5 have been shifted by 2, 4, 6, and 8 scale units (mS/cm), respectively.Highlights► Micellization of AMT studied at different fixed temperatures and KCl concentrations in aqueous solutions. ► The cmc of AMT increases with increasing temperature and decreasing with KCl concentration. ► The thermodynamic parameters are evaluated which clearly indicate more stability of the AMT solution in presence of KCl. ► Influence of KCl on the cloud point has been studied and energetic parameters are evaluated. ► The results have relevance in drug delivery/model drug delivery.

The present work was undertaken with a view to understand the influence of a model non-ionic tri-block copolymer PEO–PPO–PEO (poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide)) with molecular weight 5800 i.e., P123 [(EO)20–(PO)70–(EO)20] on the self-aggregation characteristics of the anionic surfactant sodium dodecylsulfate (SDS) in aqueous solution (D2O) using NMR chemical shift, self-diffusion and nuclear spin-relaxation as suitable experimental probes. In addition, polymer diffusion has been monitored as a function of SDS concentration. The concentration-dependent chemical shift, diffusion data and relaxation data indicated the significant interaction of polymeric micelles with SDS monomers and micelles at lower and intermediate concentrations of SDS, whereas the weak interaction of the polymer with SDS micelles at higher concentrations of SDS. It has been observed that SDS starts aggregating on the polymer at a lower concentration i.e., critical aggregation concentration (cac = 1.94 mM) compared to polymer-free situation, and the onset of secondary micelle concentration (C2 = 27.16 mM) points out the saturation of the 0.2 wt% polymer or free SDS monomers/micelles at higher concentrations of SDS. It has also been observed that the parameter cac is almost independent in the polymer concentrations of study. The TMS (tetramethylsilane) has been used as a solubilizate to measure the bound diffusion coefficient of SDS–polymer mixed system. The self-diffusion data were analyzed using two-site exchange model and the obtained information on aggregation dynamics was commensurate with that inferred from chemical shift and relaxation data. The information on slow motions of polymer–SDS system was also extracted using spin–spin and spin–lattice relaxation rate measurements. The relaxation data points out the disintegration of polymer network at higher concentrations of SDS. The present NMR investigations have been well corroborated by surface tension and conductivity measurements.Graphical abstractSDS self-aggregation characteristics in the absence and presence of the PEO–PPO–PEO tri-block copolymer [(EO)20–(PO)70–(EO)20], and also copolymer aggregation features in the presence of SDS, investigated using NMR diffusometry.Highlights► NMR diffusion study provides an opportunity to demonstrate polymer–surfactant interactions in distinct regimes of SDS. ► The obtained micelle pertinent parameters like cmc and hydrodynamic radius reveal the binding nature of polymer to SDS. ► The onset of secondary micelle concentration (C2) of SDS. ► The disintegration of polymer at higher SDS concentrations. ► The NMR results well corroborated by surface tension and conductivity data.

In this paper, we report the preparation and characterization of mesoporous and biocompatible transparent silica aerogel by the sol–gel polymerization of tetraethyl orthosilicate using ionic liquid. Choline cation based ionic liquid allows the silica framework to form in a non collapsing environment and controls the pore size of the gel. FT-IR spectra reveal the interaction of ionic liquid with surface –OH of the gel. DSC thermogram giving the evidence of confinement of ionic liquid within the silica matrix, which helps to avoid the shrinkage of the gel during the aging process. Nitrogen sorption measurements of gel prepared with ionic liquid exhibit a low surface area of 100.53 m2/g and high average pore size of 3.74 nm. MTT assay proves the biocompatibility and cell viability of the prepared gels. This new nanoporous silica material can be applied to immobilize biological molecules, which may retain their stability over a longer period.Graphical abstractThe use of choline based ionic liquid to sol–gel system, allows the silica framework to form in a non collapsing environment and avoids the shrinkage of the gel. Presence of ionic liquid in silica mesoporous materials enhanced the cell viability and proliferation. This sol–gel could be applied to immobilize biological molecules and respond to the external analytes.Highlights► The preparation of silica aerogel by the sol–gel polymerization process of tetraethylorthosilicate using a biocompatible choline formate ionic liquid. ► For the first time, we report the choline based ionic liquid used to the sol–gel system. ► Ionic liquids could be used to stabilize and solubilize biomolecules such as proteins, enzymes, etc.; so these aerogels could be used to encapsulate biomolecules. ► Choline ionic liquids have plastic crystalline behavior; these sol–gel systems can give better performance in electrochemical devices.

The aggregation behavior and interaction of an amphiphilic antidepressant drug imipramine (IMP) hydrochloride with the cationic surfactant cetyltrimethylammonium bromide (CTAB) have been studied using light scattering (both static and dynamic) techniques. Due to rigid tricyclic hydrophobic moiety present in the molecule, the drug shows interesting association behavior. The static light scattering measurements show that the self-association of IMP commenced above a well-defined critical micellar concentration (CMC), which decreases with increasing the mole fraction of the CTAB surfactant. Both the excess Gibbs energy (ΔGex) and the Gibbs energy of micellization (ΔGM°) are negative, and decrease with increasing mole fraction of the surfactant. The hydrodynamic diameters (dh) of the micellar aggregates were also evaluated using the dynamic light scattering measurements. The data indicate formation of larger aggregates by IMP and CTAB due to mixed micellization and subsequent micellar growth. The results have been analyzed using different models (viz., Clint, Motomura, Rosen, Rubingh, etc.) for mixed micelle formation.Graphical abstractHighlights► Aggregation/mixed micellization of IMP drug with CTAB has been studied by SLS/DLS. ► The SLS measurements show that the self-association of IMP commenced above CMC. ► The CMC value decreases with increasing the mole fraction of the CTAB surfactant. ► Both ΔGex and ΔGM° are negative, and decrease with increasing mole fraction of CTAB. ► The hydrodynamic diameters (dh) of the micellar aggregates were evaluated using the DLS measurements.

In the present paper, we report the micellization, aggregation behavior and thermodynamics of a cationic surfactant viz. cetyltrimethylammonium bromide (CTAB) in absence and presence of tyrosine-hydantoin (TH) drug. The solution behavior of the mixture of CTAB and TH drug has been determined using conductivity, surface tension, UV–visible and fluorescence spectroscopic methods. A strong interaction between the two amphiphiles is indicated from the above measurements. The critical micelle concentration (cmc) of CTAB is found to decrease with increase in the amount of TH in the mixture. The cmc values obtained by these methods are in good agreement with each other. The critical micelle concentration, aggregation number and standard free energy changes of aggregation of the surfactant (CTAB) in aqueous solution in absence and presence of TH are evaluated at different temperatures (294, 303 and 318 K). The aggregation number is obtained by the steady-state fluorescence spectroscopic method. Thermodynamic parameters (the standard Gibbs energy change of micellization, ΔG ° m, the standard enthalpy change of micellization, ΔH ° m, the standard entropy change of micellization, ΔS ° m, the standard Gibbs (transfer) energy, (ΔG°m)tr, and the excess free energy change of micellization, ΔGex) have been evaluated. The negative values of standard Gibbs energy change indicate spontaneous micellization and synergism. The interaction parameter, βm, activity coefficients (f1, f2) have been evaluated, and using these data we evaluated excess Gibbs energies, which indicate the spontaneity and the stability of the mixed micelles.

The aggregation properties of Tyr-Phe dipeptide and Val-Tyr-Val tripeptide were studied in aqueous solution and in the presence of SDS and SDS–polymer environments using UV–visible, surface tension, fluorescence and circular dichroism (CD) techniques. Both the peptides formed micelles. The cmc values obtained for dipeptide and tripeptide are 2 × 10−5 and 4 × 10−5 M, respectively in aqueous solution at 25 °C. The presence of additives (SDS and polymer) hindered the micelle formation of peptides. The cmc values obtained by various methods are in good agreement with each other. Effect of peptides on the aggregation properties of SDS also was investigated. The cmc of SDS was decreased in presence of peptides and were reduced with increase in temperature. Using monophasic micellization concept, the association constant (KA) for the SDS–peptide mixed micellar systems was determined. Using biphasic model, the thermodynamic parameters viz; ΔG°m, ΔH°m and ΔS°m for SDS–water and SDS–peptide–water mixed micellar systems, the standard free energy for transfer of SDS from aqueous to peptide additive environments were estimated at various temperatures. These results suggest that the SDS is more stable in micellized form in the SDS–water–peptide ternary systems compared to the situation in the corresponding SDS–water binary systems.Graphical abstractThe aggregation properties of Tyr-Phe dipeptide and Val-Tyr-Val tripeptide were determined in aqueous solution. Plot of fluorescence intensity vs concentration of peptides at 25 °C.Research highlights▶ For the first time we have demonstrated that the Tyr-Phe dipeptide and Val-Tyr-Val tripeptide form micelles in aqueous solution. ▶ The interactions of these peptides with SDS and PEO–PPO–PEO triblock copolymer were studied. ▶ The thermodynamic parameters of the peptide micelles and their mixed systems were evaluated.

In the present paper, we report the micellization at different fixed temperatures [(293.15, 303.15, 313.15, and 323.15) K] and the clouding behavior of the phenothiazine drug 10-[2-(dimethylamino)propyl]phenothiazine hydrochloride (promethazine hydrochloride, PMT) in the absence and presence of KCl. The critical micelle concentration (cmc) of PMT was measured by the conductivity method. The cmc values decrease with increasing the KCl concentration, whereas with increasing temperature, the cmc values increase. The thermodynamic parameters, namely, the standard Gibbs energy (ΔmG°), standard enthalpy (ΔmH°), and standard entropy (ΔmS°) of micellization of PMT were evaluated, and they indicate greater stability of the PMT solution in the presence of KCl. PMT shows phase separation also. The cloud point (CP) of PMT decreases with increasing pH because of deprotonation of the drug molecules. The CP values increase with increasing KCl as well as PMT concentration because of micellar growth. Furthermore, the thermodynamic parameters were evaluated at the CP.

In the present paper, we report the thermodynamics of the four amphiphilic drugs (two antidepressants, amitriptyline hydrochloride and imipramine hydrochloride, and two phenothiazines, chlorpromazine hydrochloride and promethazine hydrochloride) in the presence of additives [NaCl, cetyltrimethylammonium bromide (CTAB), polyethylene glycol t-octylphenyl ether (TX-100)] and evaluated Gibbs energies [at the air/water interface (Gmin(s)), the standard Gibbs energy change of micellization (ΔmicG0), the standard Gibbs energy change of adsorption (ΔadsG0), and the excess free energy change of micellization (ΔGex)].

5,5-Acetamidomethyl-5-methylimidazolidine-2,4-dione shows antimicrobial activity against bacteria at millimolar concentrations well above its critical micellar concentration (cmc). Two-dimensional surface properties were investigated using Langmuir Film Balance to understand the membrane-active nature and nanomaterial behavior of this hydantoin derivative. Hydantoin forms an expanded nanofilm at air–water interface. The maximum limiting surface area (A0) and collapse pressure (πc) are dependent on hydantoin concentration. Hydantoin undergoes a change in orientation at the interface, in the pressure region 2.5 and 7.5 mN m−1, corresponding to surface areas 51–15 and 41–12 Å2 molecule−1, respectively. A large collapse pressure (πc) in LB film indicates a role for hydrophobic interactions in the self-assembly of hydantoin. Surface areas computed using Connolly method, are in good agreement with the experimental results. Monolayer studies suggest a dispersed state for hydantoin when its concentration is below cmc, suggesting a mechanism for the observed bacteriostatic activity of hydantoin. In the present study, it has been found for the first time that the minimum inhibitory concentration (MIC) of the hydantoin is very close to its cmc.

At the cloud point (CP, where phase separation occurs), the thermodynamic properties of aqueous buffer solution of the amphiphilic phenothiazine drug promethazine hydrochloride (PMT) are calculated in the presence of various additives (viz., alcohols, surfactants, and polymers). PMT undergoes clouding phenomena, which depend upon the physicochemical conditions (e.g., concentration, pH, temperature, etc.). As the clouding components release their solvated water, they separate out from the solution. Therefore, the CP of an amphiphile can be considered the limit of its solubility. Herein, we report the thermodynamics of clouding in PMT in the presence of additives. The standard Gibbs energy change of solubilization (ΔsG0) for all of the additives is found to be positive. However, the standard enthalpy change (ΔsH0) and the product of temperature and the standard entropy change (TΔsS0) values are negative as well as positive depending upon the type and nature of the additive. The results are discussed on the basis of these factors.

An amphiphilic drug chlorpromazine hydrochloride (CPZ), a phenothiazine with neuroleptic activity, undergoes clouding phenomena, which depend upon the physicochemical conditions (e.g., concentration, pH, temperature, etc.). The clouding components release their solvated water and separate out from the solution. Therefore, the cloud point (CP) of an amphiphile can be considered as the limit of its solubility. Herein, we report the energetics of clouding in CPZ in the presence of additives (viz., alcohols, surfactants, and polymers). The standard Gibbs energy change of solubilization (ΔG0s) for all of the additives is found to be positive. However, the standard enthalpy change (ΔH0s) and the product of the temperature and the standard entropy change (TΔS0s) values are negative as well as positive, depending upon the type and nature of the additive, and the results are discussed on the basis of these factors.

Mixed self-assembled monolayer of thiols were formed on the electrode surface using aromatic and aliphatic thiols and the modified interface were used to demonstrate charge trapping behavior at the modified interface. The electrode surface was modified by two schemes. In Scheme 1, electrode surface modified with methylene blue (MB) shows charge trapping behavior when contacts the electrolyte containing potassium ferricyanide. In Scheme 2, a redox-active bilayer is constructed using hexamineruthenium (II) chloride and methylene blue. This redox-active bilayer assembly exhibits unidirectional flow of current.

Self-assembling characteristics of a hydantoin drug are determined using UV–visible spectroscopy, surface tension, conductivity and fluorescence methods. The critical micelle concentration (cmc) obtained by these methods are in good agreement with each other. The critical micelle concentration, aggregation number and standard free energy change of aggregation of the hydantoin in aqueous solution are 1.5 mM, 8 ± 1 and −15.9 kJ mol−1, respectively, at 22 °C. The aggregation number obtained by both steady-state and time-resolved fluorescence spectrophotometric methods are in good agreement with each other. Pyrene fluorescence quenching rate constants in hydantoin micelles with varying amount of quencher in the absence and presence of oxygen are found to be 6.2 ± 0.3 × 109 and 1.7 ± 0.2 × 1010 M−1 s−1, respectively. Furthermore, here we have for the first time investigated that there is no need of adding any external fluoroprobe for the determination of the aggregation number of the micelles if the micelle forming substance contains a fluorescent excited state. The accessibility of the quencher to the total fluorescence in hydantoin micelles in the absence and presence of external probe viz. pyrene has also been estimated.

•Fungal protein mediated green synthesis of silver nanocomposite has been developed.•The silver nanocomposite ruptured the bacterial cell membrane and released intracellular materials.•The silver nanocomposite inhibited the respiratory chain dehydrogenase and metabolic activity of the cells.•The silver nanocomposite fragmented the DNA and down regulated protein expression.•The silver nanocomposite exhibited ROS independent particle specific antibacterial activity.The biosynthesis of nano-silica silver nanocomposite (NSAgNC) and it is as antibacterial effect on gram-negative bacteria viz. Escherichia coli and Pseudomonas aeruginosa has been investigated for disinfection of water. The as-synthesized NSAgNC exhibited antibacterial activity in a dose dependent manner and ∼99.9% of E. coli and P. aeruginosa were killed at a concentration of 1.5 mg/mL of NSAgNC (5.1 wt% Ag) within 5 h. The NSAgNC showed similar antibacterial activities both in oxic and anoxic conditions. The results further demonstrated that NSAgNC exhibited reactive oxygen species (ROS) independent “particle specific” antibacterial activity through multiple steps in absence of leached out Ag+ ions. The initial binding of NSAgNC on the cell wall caused loss of cell membrane integrity and leakage of cytoplasmic materials. Inhibition of respiratory chain dehydrogenase by NSAgNC caused metabolic inactivation of the cells and affecting the cell viability. Genomic and proteomic studies further demonstrated the fragmentations of both plasmid and genomic DNA and down regulation of protein expression in NSAgNC treated cells, which leading to the cell death. Thus the biosynthesized NSAgNC has great potential as disinfectant for water purification while minimizing the toxic effects.Download full-size image

Polymer functionalized surfaces are important components of various sensors, solar cells and molecular electronic devices. In this context, the use of self-assembled monolayer (SAM) formation and subsequent reactions on the surface have attracted a lot of interest due to its stability, reliability and excellent control over orientation of functional groups. The chemical reactions to be employed on a SAM must ensure an effective functional group conversion while the reaction conditions must be mild enough to retain the structural integrity. This synthetic constraint has no universal solution; specific strategies such as “graft from”, “graft to”, “graft through” or “direct” immobilization approaches are employed depending on the nature of the substrate, polymer and its area of applications. We have reviewed current developments in the methodology of immobilization of a polymer in the first part of the article. Special emphasis has been given to the merits and demerits of certain methods. Another issue concerns the utility – demonstrated or perceived – of conjugated or non-conjugated macromolecules anchored on a functionally decorated SAM in the areas of material science and biotechnology. In the last part of the review article, we looked at the collective research efforts towards SAM-based polymer devices and identified major pointers of progress (236 references).

Incorporation of the triazolyl moiety modulates the basicity and effective size of the chelating ring, changes the stoichiometry in complex formation and thereby imparts Cu2+ ion selectivity.

Two new rhodamine based probes 1 and 2 for the detection of Fe3+ were synthesized and their selectivity towards Fe3+ ions in the presence of other competitive metal ions tested. The probe 1 formed a coloured complex with Fe3+ as well as Cu2+ ions and revealed the lack of adequate number of coordination sites for selective complexation with Fe3+. Incorporation of a triazole unit to the chelating moiety of 1 resulted in the probe 2, that displayed Fe3+ selective complex formation even in the presence of other competitive metal ions like Li+, Na+, K+, Cu2+, Mg2+, Ca2+, Sr2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+, Cd2+, Hg2+ and Pb2+. The observed limit of detection of Fe3+ ions (5 × 10−8 M) confirmed the very high sensitivity of 2. The excellent stability of 2 in physiological pH conditions, non-interference of amino acids, blood serum and bovine serum albumin (BSA) in the detection process, and the remarkable selectivity for Fe3+ ions permitted the use of 2 in the imaging of live fibroblast cells treated with Fe3+ ions.

“Click” polymerization reaction has been performed on the functional self-assembled monolayer to incorporate polytriazoles. Ellipsometric and atomic force microscopic studies indicated a high degree of polymerization and fairly dense surface coverage. Band gap calculation revealed the possibility of its use as a semiconducting material.

The present investigation attempts at fabricating collagen-based scaffolds impregnated with sago starch capped silver nanoparticles (AgNPs), useful for biomedical applications, and aims at studying their physicochemical aspects. AgNPs synthesized through a chemical reduction method, capped using different concentrations of sago starch, are incorporated into collagen derived from fish scales, and lyophilized to form scaffolds. FT-IR spectra confirm and validate the interaction of sago starch capped AgNPs with collagen in the scaffolds. TGA and DSC results indicate enhanced thermal stability of collagen scaffolds impregnated with sago capped AgNPs compared to collagen alone. All the collagen scaffolds containing sago starch capped AgNPs show high tensile strength values for their use as wound dressing materials. Moreover, lower minimum inhibitory concentration values are obtained for the above capped AgNP collagen scaffolds, which indicate higher antibacterial activities compared to uncapped AgNPs tested against both gram positive and negative bacterial strains. The novelty is that the developed scaffolds are biodegradable and in vitro studies reveal them as biocompatible and suitable for tissue regeneration applications.

The influence of water-insoluble nonionic triblock copolymer PEO–PPO–PEO [poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide)] i.e., E6P39E6 with molecular weight 2800, on the microstructure and self-aggregation dynamics of anionic surfactant sodium dodecylsulfate (SDS) in aqueous solution (D2O) were investigated using high resolution nuclear magnetic resonance (NMR) and small-angle neutron scattering (SANS) measurements. Variable concentration and temperature proton (1H), carbon (13C) NMR chemical shifts, 1H self-diffusion coefficients, 1H spin–lattice and spin–spin relaxation rates data indicate that the higher hydrophobic nature of copolymer significantly influenced aggregation characteristics of SDS. The salient features of the NMR investigations include (i) the onset of mixed micelles at lower SDS concentrations (<3 mM) relative to the copolymer-free case and their evolution into SDS free micelles at higher SDS concentrations (∼30 mM), (ii) disintegration of copolymer–SDS mixed aggregate at moderate SDS concentrations (∼10 mM) and still binding of a copolymer with SDS and (iii) preferential localization of the copolymer occurred at the SDS micelle surface. SANS investigations indicate prolate ellipsoidal shaped mixed aggregates with an increase in SDS aggregation number, while a contrasting behavior in the copolymer aggregation is observed. The aggregation features of SDS and the copolymer, the sizes of mixed aggregates and the degree of counterion dissociation (α) extracted from SANS data analysis corroborate reasonably well with those of 1H NMR self-diffusion and sodium (23Na) spin–lattice relaxation data.

Novel bio-renewable castor oil based polyurethane (PU)–silica nanocomposite films were prepared using castor oil, 1,6-hexamethylene diisocyanate and dibutyltin dilaurate in tetrahydrofuran at room temperature. ATR-FTIR spectra confirm the formation of polyurethane and the presence of silica nanoparticles in the polyurethane matrix. The increase of Si nanoparticle content shifts the peak position of N–H and CO (both hydrogen and non-hydrogen bonded) groups present in the polyurethane structure. Furthermore, Raman spectra confirmed the urethane–amide interaction present in the polyurethane–silica nanocomposites. 29Si CP/MAS NMR spectra evidence the formation and the presence of completely condensed SiO2 species in the polyurethane nanocomposite films. The incorporation of silica nanoparticles increases the thermal stability of the above-mentioned polyurethane films, which can be seen from the increase in activation energy (Ea) values of the degradation process. The Ea values at two stages (Tmax1 and Tmax2) of the degradation process are 133, 139 and 157, 166 kJ mol−1 for PU control and PU-5AMS (5 wt% amine modified silica nanoparticles), respectively. DSC results prove the interfacial interaction present between silica nanoparticles and the polyurethane hard segment, which decreases the melting temperature. Optical transmittance of the polyurethane films decreased with increasing silica content due to the scattering at the interfaces between the silica nanoparticles and polyurethane. It is interesting to note that the presence of silica nanoparticles gives reinforcement to polyurethane film, thereby increasing the storage modulus up to 24% for PU-5AMS. FE-SEM and HR-TEM images confirm the presence of silica nanoparticles in the polyurethane matrix.

Peptide based self-assembled structures, especially those from smaller peptides, have attracted much research interest due to their potential applications as biomaterials. These structures have been produced using different solvents (one of the methods), including alcohols, except fluorinated alcohols, which are believed to support non-aggregated structures. Herein, we have studied the ability of 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) solvents to induce self-assembly of an aromatic dipeptide, namely Tyr–Phe (YF). SEM images showed that HFIP and TFE can induce self-assembly with completely different morphologies, namely microribbons and microspheres, respectively, when YF is dried on a glass surface. Optical microscopic images showed that the microribbons possess birefringence under polarized light, whereas the microspheres do not, indicating that the self-assembled structures derived from HFIP solution are more highly ordered and crystalline in nature than those derived from TFE. Spectroscopic results indicated that the YF peptide adopts completely different conformations in these solvents. Time-dependent experiments suggested that the conformation of YF in HFIP is kinetically unstable and undergoes conformational change, whereas it is more stable in TFE, demonstrating that the modes of interaction of the TFE and HFIP solvents with the peptide are dissimilar. Different self-assembled structures were observed at different time intervals when YF was incubated in neat HFIP and 10% HFIP–90% TFE, establishing that the monomeric conformation plays a dominant role in deciding the final self-assembled structure (morphology) of YF. The current results demonstrate that TFE and HFIP solvents can produce self-assembled structures with different morphologies during solvent evaporation, despite their similar properties, such as secondary structural (α-helix) induction and preserving the peptide in its monomeric conformation in solution.

The static 1D 13C and 2D Proton Encoded Local Field (PELF) NMR experiments are carried out in the nematic phase of a less viscous liquid crystal 4-(trans-4′-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT) with a view to find orientational order. The PELF spectra provide better resolution which facilitates the assignment of cyclohexyl and phenyl ring carbons relatively easy. For the cyclohexyl unit, four pairs of dipolar splitting are clearly noticed in contrast to earlier reports on structurally similar mesogens where only two pairs of doublets are seen. The linear relationship between anisotropic chemical shifts and orientational order is established and semi-empirical parameters are obtained to aid the study of the order behaviour of 6CHBT over the entire nematic range. The data further fitted to the Haller equation and a reasonably good agreement is observed. The temperature dependence trends of orientational order parameters extracted for various carbons using 13C–1H dipolar couplings with those of 13C chemical shifts are compared. A gradual decrease in the order parameter is noticed for different molecular segments while traversing from the core to the aliphatic chain via the cyclohexyl ring. The notable decreasing trends of order parameters along the chain are observed similar to those of the corresponding phenyl cyclohexanes reported earlier.