•Rational design and assemble of new bimetallic based chemodosimeters.•The Re(I)-Pt(II) complex is a good food detector for volatile biogenic sulfides.•Naked-eye luminescent responses specific to CH3SH and CH3SCH3 by the food detector to check the freshness of meat.•Applicable for in-situ CH3SH monitoring in real rotten pork samples and as efficient as GCMS detection.Detection of volatile biogenic sulfides (VBS) plays a crucial role in food safety because the amounts of these compounds can reflect the freshness of meat. A new indicator-displacement assay with Re(I)-Pt(II) complexes, [Re(Lig)(CO)3(bridge)]–[Pt(DMSO)(Cl)2] (1: Lig = 5-phenyl-1,10-phenanthroline and bridge = NCS−; 2: Lig = 5-phenyl-1,10-phenanthroline and bridge = CN−; 3: Lig = 2,2′-biquinoline and bridge = NCS−), was demonstrated to be a very effective sensing method to VBS. The results indicated that the control of Re(I)–bridge–Pt(II) and Re(I)–ligand combination are able to regulate their sensing selectivity and sensitivity. This system was successfully applied to detect CH3SCH3 in real rotten pork with a linear luminometric response up to 20.0 mg kg−1 (R = 0.997) with the detection limit as 0.05 mg kg−1. Complex 1 also gave comparable results on the detection of VBS with respect to those determined by GCMS with recovery range from 76% to 102% (RSD% = 13.8).

•Molecular imprinting-based fluorescent and solvatochromic chemosensor was synthesized.•Chemosensor 1 exhibits a turn-off fluorescent response toward phthalate esters in ethanol.•Chemosensor 2 shows solvatochromic properties.•Chemosensor 2 displays fluorescent-enhancing and colorimetric response toward DBP.This paper reports a molecular imprinting-based fluorescent and solvatochromic multifunctional chemosensor for phthalate esters (PAEs). The multifunctional chemosensor was fabricated through precipitation polymerization using 4-[(1E)-4-(2-hydroxyphenyl) ethenyl]-1-allylpyridinium bromide (HPEAPB) as the functional monomer and phthalamide-4,4′-dibutyl dimethyl ester (PDDB) as the mimic template. The molecular imprinting-based chemosensor shows specific affinity toward PDDB and dibutyl phthalate (DBP) in ethanol. Of note is that the molecular imprinting-based chemosensor shows turn-off fluorescent response toward PAEs in an ethanol solution with a limit of detection of 2.0 × 10−6 mol L-1 (0.7 ppm) when HPEAPB is in the protonated form (chemosensor 1), and shows solvatochromic properties, fluorescent enhancement and a colorimetric (from orange to bright yellow) response toward PAEs in an ethanol solution with a limit of detection of 4.0 × 10−5 mol L-1 by the naked eye when HPEAPB is in the deprotonated form (chemosensor 2). This multifunctional chemosensor is promising for the simple, accurate and low-cost detection of trace PAEs.

•A product-imprinted polymer based organocatalyst was developed.•The organocatalyst is amphiphilic and photoswitchable.•The catalyst catalyzes aldol reaction with good conversion and low catalyst loading.•The catalyzed aldol reaction performs well in a mixed solvent of DMSO and water.A series of amphiphilic molecularly imprinted polymers (MIP1, MIP2, MIP3, MIP4, MIP5, and MIP6) containing hydrophobic photoresponsive sites and hydrophilic catalytically active sites were fabricated using bifunctional monomers. These polymers were characterized by scanning electron microscopy, N2 adsorption–desorption analysis, Fourier Transform infrared spectroscopy, thermal gravimetric analysis, and ultraviolet–visible spectroscopy. The catalytic activity of the amphiphilic molecularly imprinted polymer was investigated towards the aldol reaction between p-nitroaldehyde and acetone (a molecular enlargement reaction) in a mixed solvent of DMSO and water at room temperature. The polymer catalyst MIP3 performs best, and displayed good conversions with low catalyst loading (5 mol% of l-hydroxyproline with respect to the aldehyde) and photoswitching properties (photo-regulated conversion difference of 20%). Compared with the corresponding non-imprinted polymer, a higher binding capacity, higher conversion, and better photoswitching properties were obtained when the molecularly imprinted polymer was used as the catalyst, illustrating the importance of the specific cavities in the molecularly imprinted polymer.Download full-size image

•A novel water-soluble azobenzene derivative MAPADSA was synthesized.•A photoresponsive SMIP was fabricated on sacrificial silica microspheres.•A photoresponsive hollow MIP was obtained after removal of the silica core.•Photoresponsive hollow MIP displayed better properties than photoresponsive SMIP.•PHMIP was used to determine trace triamterene in biological samples (LOD: 0.1 ppm).This paper reports a photoresponsive hollow molecularly imprinted polymer for the determination of trace triamterene in biological sample. The photoresponsive hollow molecularly imprinted polymer was prepared on sacrificial silica microspheres via surface imprinting technique through atom transfer radical polymerization using a novel water-soluble azobenzene derivative, 4-[(4-methacryloyloxy)phenylazo]-3,5-dimethyl benzenesulfonic acid, as the functional monomer, and the sacrificial silica core was subsequently removed using HF etching method with 1.25 vol.% HF ethanolic solution. The morphologies and properties of the photoresponsive hollow molecularly imprinted polymer were further characterized and compared systematically with the corresponding photoresponsive surface molecularly imprinted polymer. Compared with surface imprinted polymer, the hollow material displayed higher binding capacity, better recognition ability, faster mass-transfer rate, and larger isomerization rate constants toward triamterene. The static binding properties of the imprinted materials were investigated under three irradiation conditions. The photoresponsive hollow molecularly imprinted polymer showed better specificity toward triamterene than its structural analogues (folic acid and caffeine) as examined by UV–vis and HPLC. The photoresponsive hollow molecularly imprinted polymer was utilized for the determination of trace triamterene in biological samples (human urine and serum) with advantages of simple sample pre-treatment, good recovery and good sensitivity.Download high-res image (303KB)Download full-size image

•Pyridinium-salt-based electrochromic materials, AETPDs, were designed and synthesized.•AETPDs exhibit dual-color and good electrochromic properties.•The carboxylic acids and N-substituents greatly influence their electrochromic properties.This study aims to achieve dual-color properties for pyridinium-salt-based electrochromic materials. A novel series of 4′-(4-alkyl ester)-4,2′:6′,4″-terpyridinium derivatives were designed and synthesized through the introduction of an ester group onto the benzene ring of 2,4-di(4-pyridyl)-4-benzylpyridinium derivatives. Dual-electrochromic devices based on these compounds were fabricated. Multiple shades of green and yellowish green colors were obtained by changing the type of carboxylic acids and the nitrogen substituents. The type of carboxylic acids and the nitrogen substituents significantly influenced their electrochromic properties. 4′-(4-Alkyl ester)-4,2′:6′,4″-terpyridinium derivatives show good electrochromic properties such as high coloration efficiency, reasonable contrast, satisfactory optical memories, and redox stability. The dual-electrochromic materials are promising candidates for applications in electrochromic display systems.Download high-res image (117KB)Download full-size image

A photoresponsive hollow molecularly imprinted polymer (PHMIP) was fabricated for photoresponsive recognition and determination of trace bisphenol A (BPA) in aqueous media using a water-soluble azo compound as the functional monomer. The PHMIP was prepared on sacrificial silica microspheres by surface imprinting and subsequent removal of the silica core. The PHMIP displayed photocontrolled recognition for BPA. SEM, TEM, FT-IR, TGA and N2 adsorption-desorption analyses confirmed successful formation of the hollow structure. The PHMIP displayed higher binding capacity, a larger specific area, and faster mass transfer rate than its corresponding surface molecularly imprinted polymer. The PHMIP was used to determine trace BPA in real samples with a limit of detection of 0.5 ppm. For samples spiked at 0–10 ppm, the BPA recoveries were in the range of 93.0%–99.0%. This PHMIP-based method provides convenient and inexpensive detection method for trace BPA in environmental samples. This method is especially suitable for determining materials that do not possess specific spectroscopic or luminescent properties.

•Protonated Brooker's Merocyanine functionalised polymer microspheres was designed.•The microspheres display colorimetric and fluorescent sensing properties toward CN–.•The microspheres can be reversed for many times for monitoring and detection of CN–.•The microspheres are applicable for determination of CN– in real samples.This paper describes the development of a colorimetric and fluorescent cyanide probe based on crosslinked polymer microspheres functionalized with a protonated merocyanine. The functionalised microspheres were prepared by free radical polymerization using 4-((E)-2-[(4-hydroxylphenyl) ethenyl-1-allyl pyridinium bromide as the functional monomer, ethylene glycol dimethacrylate as the crosslinker, and azobisisobutylnitrile as the radical initiator. Upon introducing CN– to a suspension of the functionalised microspheres in ethanol/H2O (9:1, v/v), a change from yellow to red and a decrease in fluorescence intensity at 497 nm were immediately observed. This CN– probe can be reversed many times, which is cost efficient and beneficial to the environment. Analytical application of the functionlised microspheres to measure CN– concentration in spiked water samples was explored with good recoveries. Thus, the colorimetric and fluorescent CN− probe has high potential for the ultrasensitive detection of CN− in real samples.

•A novel photoresponsive molecularly imprinted polymer (MIP) for selective recognition of guanine in aqueous media is developed.•The MIP displays good selectivity toward guanine over other competing compounds.•The MIP can efficiently extract guanine from complicated beer and then photocontrolled release it in aqueous media for quantitative analysis.A novel photoresponsive molecularly imprinted polymer (MIP) was developed for the selective extraction of guanine from complex samples. The photoresponsive MIP was fabricated using guanine as the template, water-soluble 5-[(4-(methacryloyloxy)phenyl)diazenyl]isophthalic acid as the functional monomer, and water-soluble triethanolamine trimethacrylate as the cross-linker. The MIP displayed good selectivity toward guanine with a dissociation constant of (2.70 ± 0.16) × 10−5 mol L−1 in aqueous media. The density of the guanine-specific receptor sites in the MIP material was (4.49 ± 0.22) μmol g−1. Quantitatively release and uptake of guanine by the MIP occured with irradiation at 365 and 440 nm, respectively. The MIP could efficiently extract guanine from beer and then release it into aqueous media under photocontrol. This method could be used for selective separation and subsequent determination of a specific analytes from complex samples.

An L-proline-catalyzed aldol reaction was photo-controlled using an L-proline-imprinted polymer containing azobenzene. Upon UV irradiation, azobenzene chromophores underwent trans → cis isomerization, thereby releasing L-proline to catalyze the aldol reaction.

A colorimetric cyanide ion (CN−) sensor 4-[(1E)-2-(2-hydroxyphenyl)ethenyl]-1-allylpyridinium bromide (2-HPEAPB) was synthesized via condensation and N-alkylation reactions using 4-methylpyridine and salicylaldehyde as the starting materials. 2-HPEAPB displayed good selectivity, fast response, and high sensitivity toward CN− over other competing anions in acetonitrile–water (95:5, v/v) with a limit of detection of 8.0 × 10−6 mol L−1 by the naked eye. The sensing mechanism and the influence of pH and temperature on sensing properties were investigated. Colorimetric test paper for CN− was prepared by absorption of 2-HPEAPB to a chromatography paper, which could be used to detect CN− directly and quickly. Analytical application of measuring CN− concentration in an electroplating wastewater in real-time was conducted successfully.

•A colorimetric chemodosimeter (AHPEQB) based on quinolinium for cyanide ion was designed.•AHPEQB displays rapid response, good sensitivity, reversibility and selectivity toward cyanide ion among other competing anions in ethanol.•AHPEQB can be used for the ultrasensitive determination of cyanide ion concentration in real samples.A novel colorimetric chemodosimeter for cyanide (CN−) and 1-allyl-4-[2-(4-hydroxyphenyl)ethenyl)]-quinolinium bromide (AHPEQB) was designed and synthesized by condensation and terminal N alkyl reaction. AHPEQB exhibited highly selective and sensitive recognition properties toward CN− over other competing anions in ethanol, a protic solvent, with a 1:1 binding stoichiometry and a detection limit of 1.7 × 10−6 mol L−1. AHPEQB also displayed rapid colorimetric response that could be readily observed by the naked eye and good reversibility. The sensing mechanism of the proposed chemodosimeter was studied by UV–Vis, 1H NMR titration, and comparison 1-allyl-4-[2-(4-acetoxyphenyl)ethenyl)]-quinolinium bromide (AAPEQB). The colorimetric chemodosimeter showed high accuracy in determining the concentration of CN− in real water samples.

A novel turn-on fluorescent synthetic molecular probe for Hg2+ sensing in water based on 8-hydroxyquinoline is presented.

This Letter aimed to develop an efficient method for the determination of cyanide ion (CN−). A novel colorimetric chemosensor 4-[(1E)-2-(4-hydroxyphenyl)ethenyl]-1-allylpyridinium bromide (HPEAPB) was synthesized. HPEAPB displayed good selectivity toward CN− over other competing anions in ethanol. A color change from yellow to red was immediately observed upon the addition of CN− and the limit of detection (LOD) was 3.4 × 10−6 mol L−1. The sensing mechanism was discussed by UV–vis, 1H NMR titration, and a comparison study. Colorimetric test paper for CN− was prepared by attaching HPEAPB to a chromatography paper, which could be used to detect CN− in environmental samples as simply as a pH-indicator paper for pH value. The LOD of the test paper for CN− was 2.0 × 10−4 mol L−1. This detection method for CN− has potential applications in cyanide ion containing fields by combination of rapid and real-time advantages.

•A new tertiary layered assembly named GN–CD–Cyt c was prepared.•Compared with GNs and GN–CD, GN–CD–Cyt c shows improved electron transfer rate.•GN–CD–Cyt c displays high supramolecular recognition capability.This study aimed to develop a new graphene-based layered assembly, named graphene–cyclodextrin–cytochrome c with improved electron transfer rate. This assembly has combined high conductivity of graphene nanosheets (GNs), selectively binding properties and electronegativity of cyclodextrins (CDs), as well as electropositivity of cytochrome c (Cyt c). This assembly can also mimic the confined environments of the intermembrane space of mitochondria. A β-cyclodextrin (β-CD) functionalized GN (GN–CD) assembly was initially prepared by a simple wet-chemical strategy, i.e., in situ thermal reduction of graphene oxide with hydrazine hydrate in the presence of β-CD. Cyt c was then intercalated to the GN–CD assembly to form a layered self-assembled structure, GN–CD–Cyt c, through electrostatic interaction. Compared with GNs and GN–CD, GN–CD–Cyt c assembly displayed improved electron transfer rate and high supramolecular recognition capability toward six probe molecules.

The primary objective of this work is to develop a photo-responsive surface molecularly imprinted polymer (SMIP) for 2,4-dichlorophenoxyacetic acid (2,4-D) to overcome the shortcomings of conventional molecularly imprinted polymers. A photo-responsive functional monomer was firstly prepared by covalent connecting azobenzene and 2,4-D. The photo-responsive SMIP was then prepared on SiO2 nanoparticles via sol–gel process, and 2,4-D was removed via hydrolysis in acid. The SMIP shows specific affinity to 2,4-D and reversible uptake and release of 2,4-D upon alternate irradiation at 365 and 440 nm, respectively. The favorable binding strength of the imprinted receptor sites in the SMIP for 2,4-D is found to be 2.51 × 104 M−1. Density of receptor sites in the SMIP material is 10.59 μmol/g SMIP. The SMIP requires a shorter time to reach equilibrium than does the conventional molecularly imprinted polymer. The well-defined core-shell structure was clearly visualized by high resolution transmission electron microscopy.

In the present work, a conducting polymer, doped polypyrrole, was used to develop a gas sensor by dip-pen nanolithography (DPN). The response time of the sensor to 18 ppm CO2 was 9 s. The sensor response increased linearly as the CO2 concentration increased. A possible mechanism for the CO2 sensing was discussed.

A colorimetric cyanide ion (CN−) sensor 4-[(1E)-2-(2-hydroxyphenyl)ethenyl]-1-allylpyridinium bromide (2-HPEAPB) was synthesized via condensation and N-alkylation reactions using 4-methylpyridine and salicylaldehyde as the starting materials. 2-HPEAPB displayed good selectivity, fast response, and high sensitivity toward CN− over other competing anions in acetonitrile–water (95 : 5, v/v) with a limit of detection of 8.0 × 10−6 mol L−1 by the naked eye. The sensing mechanism and the influence of pH and temperature on sensing properties were investigated. Colorimetric test paper for CN− was prepared by absorption of 2-HPEAPB to a chromatography paper, which could be used to detect CN− directly and quickly. Analytical application of measuring CN− concentration in an electroplating wastewater in real-time was conducted successfully.

A novel turn-on fluorescent synthetic molecular probe for Hg2+ sensing in water based on 8-hydroxyquinoline is presented.