A novel approach was presented for the in situ synthesis of fluorescent magnetosomes by biological mineralization and carbonization processes for the first time. The surface structures, magnetism and fluorescence were studied, and the cytotoxicity tests and fluorescent trace in liposomes were probed. The fluorescent magnetosomes exhibit not only unique fluorescence and ferromagnetic properties but also low toxicity and superior imaging capability.

A simple and green method for the synthesis of fluorescent silver nanocluster–nanoparticle complexes (AgNCs–AgNPs) is presented. In this method, Ag+ was reduced to form AgNCs–AgNPs using hydrogen as the reductant and sodium polyacrylate as a soft template at room temperature. The AgNCs–AgNPs possess strong fluorescence, and the fluorescence property has high sensitivity and excellent selectivity to Ca2+. An approach based on the enhancement of fluorescence was firstly applied for the quantitative determination of Ca2+. The approach displays a wide linear response, excellent selectivity and high sensitivity, and provides a potential candidate for the quantitative determination of Ca2+ in biological systems.

New metal-free catalytic systems with carbon dots (CDs) have been presented for the degradation of thymol blue at room temperature. It was found that degradation efficiency was influenced by the pH value, the concentration of H2O2 and the addition of KI. The degradation mechanisms of catalytic systems were studied by means of electron spin resonance and a free radical quenching technique. The results show that HO˙ and ˙O2− originating from the decomposition of H2O2 in the presence of CDs contribute to the degradation of the dyes. The most important merits of the catalytic system are high degradation efficiency of thymol blue in a near-neutral solution and avoiding secondary pollution from metal ions, which make them environmentally-friendly systems for the treatment of pollutants.

Well-dispersed AuNPs@CDs nanocomposites were successfully synthesized from the reduction of chloroauric acid by carbon dots (CDs) at room temperature. The as-prepared AuNPs@CDs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), and the results indicate AuNPs@CDs nanocomposites with a core–shell structure. The AuNPs@CDs are found to possess intrinsic peroxidase-like activity, and the catalytic activity is higher than that of AuNPs. The mechanism of peroxidase-like activity of AuNPs@CDs was investigated by fluorescence spectroscopy, electron spin resonance and cyclic voltammetry, and it is found that the mechanism could be ascribed to facilitating the electron transfer between TMB and H2O2.

•High fluorescent CDs have been synthesized at room temperature.•The CDs showed superior photostability and low cytotoxicity.•The good biocompatibility of the CDs was conformed.•The CDs manifest potential for cell imaging and fluorescent staining.A simple and green approach was developed to synthesize highly fluorescent carbon dots (CDs) using albumin as a carbon source in aqueous solution at room temperature. The CDs were characterized by excellent monodispersion, superior photostability, pH-independent emission, long fluorescence lifetime and high quantum yield (QY). The photoluminescent (PL) mechanism of CDs was explored by means of time-resolved PL decay, and the results revealed that PL originated from the emission of both defect state and intrinsic state. In addition, biological imaging with the application of CDs was carried out in human breast cancer Bcap-37 cell, which demonstrated that CDs were provided with an excellent biocompatiblity, low cytotoxicity and good transmembrane ability. Besides, CDs could be considered as a potential substitute for organic dyes or semiconductor quantum dots (SQDs) in biological imaging.

An “off–on” approach for the detection of ascorbic acid using carbon dots as a fluorescent probe is presented, which is based on the fluorescence recovery of the quenched C-dots/Fe3+ complex when ascorbic acid is introduced. This sensor was also employed to determine the encapsulation efficiency of ascorbic acid in a liposome formulation.

Fluorescent hydrophobic carbon dots are synthesized in a green way and used for determination of 2,4,6-trinitrophenol in a hydrophobic medium for the first time. The approach for TNP detection realized a wide linear response, excellent selectivity and high sensitivity, which provides a potential candidate for practical TNP sensing in hydrophobic conditions.

Novel N-doped carbon dots (CDs) were synthesized. The fluorescent quantum yield of the CDs is up to 93.3%, and the fluorescence lifetime of the CDs is up to 19.50 ns. The optical properties of the CDs in various pH solutions were probed in different ways. The fluorescence characteristics of the CDs depended on change of surface structure, which was associated with pH value.

•A single phosphor with pure white light emitting are synthesized.•A facile and simple procedure is used to bind two discrete dyes to the CdS QDs.•The chromaticity of the phosphor is able to be precisely tailored.•The competition between direct excitation and FRET is inspected by fluorescence decay.A facile route to produce ternary single nanophosphors with white light is reported. This phosphor combines emission from CdS quantum dots in blue with organic dyes calcein in green and rhodamine B in orange. The chromaticity can be tailored precisely by adjusting the molar ratio of quantum dots to dyes. The phosphors are able to generate a pure white light with CIE coordinate of (x=0.33, y=0.34). The distribution of direct excitation and fluorescence resonance energy transfer (FRET) are inspected by time-resolved photoluminescence decays. The results indicate that direct excitation plays a more important role.

•A new technique to synthesize silver nanoparticles with controllable size was developed using toluene–scCO2 microemulsion.•Hydrogen was used as reducing agent in the synthesis process.•The relationship between the wavelength of maximum absorption and size of AgNPs was discussed, which was consistent with the MIE theory.A new technique to synthesize silver nanoparticles (AgNPs) with controllable size was developed using hydrogen as reducing agent in toluene–supercritical carbon dioxide (toluene–scCO2, the mixture ratio of toluene:CO2 is about 20%, v/v) microemulsion. The method involves both process of AgNPs formation (nucleation and crystal growth) at high pressure and thermal incubation at ordinary pressure in the micro-water pool of the microemulsion. Silver ions were reduced by hydrogen (H2) in the micro-reactor of toluene–scCO2 microemulsion, and the size of AgNPs can be controlled by adjusting molar ratio of water to surfactant. The size and morphology of AgNPs were characterized by DLS, TEM and AFM. The AgNPs capped with surfactant were proved by the ATR-FTIR. The relationship between the wavelength of maximum absorption and size of AgNPs was discussed, which was consistent with the MIE theory. This method is better than traditional microemulsion method to synthesize AgNPs by comparing AgNPs prepared using different methods. This method is not only able to obtain AgNPs with controllable size, but also avoids use of fluorinated reagents and reducing agent residual.

A multifunctional polydiacetylene-liposome (PDA-liposome) was prepared by self-assembly, which can be characterized with controlled drug release and fluorescence tracing. The controlled drug release was realized in both in vitro simulation and cancer cells by temperature control. The internalization and distribution of the PDA-liposome in cancer cells were presented by fluorescence cell imaging.

A novel simple and green method was developed to synthesize highly luminescent carbon dots using ascorbic acid as a carbon source in aqueous solution. The as-prepared C-dots showed downconversion and upconversion fluorescence properties. They were applied to imaging of human breast cancer cells and normal human mammary cells, showing low cytotoxicity and good biocompatibility.

A novel reversible fluorescent switch of a polydiacetylene liposome (PDA liposome) was realized by alternating heating and UV irradiation processes. The reversible fluorescence switching of the PDA liposome was mainly caused by the microstructural changes of the PDA backbone in the PDA liposomes under the alternating conditions of heating and UV irradiation.

In this study, thioglycolic acid capped-CdTe quantum dots (QDs) were modified by polyethylenimine (PEI), and then combined with fluorescein isothiocyanate (FITC) to fabricate FITC–CdTe conjugates. The self-assembly of FITC, CdTe and PEI was ascribed to electrostatic interactions in aqueous solution. The resulting conjugates were developed toward two routes. In route one, ratiometric photoluminescence (PL) intensity of conjugates (IFITC/IQDs) was almost linear toward pH from 5.3 to 8.7, and a ratiometric PL sensor of pH was favorable obtained. In route two, firstly added S2− induced remarkable quenching of QDs PL peak (at the “OFF” state), which was restored due to following addition of Cd2+ (at the “ON” state). In the conjugates, successive introduction of S2− and Cd2+ hardly influenced on FITC PL peaks. According to this PL “OFF-ON” mode, a ratiometric PL method for the detection of Cd2+ was achieved. Experimental results confirmed that the IFITC/IQDs exhibited near linear proportion toward Cd2+ concentration in the range from 0.1 to 15 μM, and the limit of detection was 12 nM. Interferential experiments adequately testified that the proposed sensors of pH and Cd2+ were practicable in real samples and complex systems. In comparison with conventional analytical techniques, the ratiometric PL method was simple, rapid, economic and highly selective.Graphical abstractHighlights► Dual-functional quantum dots were used for ratiometric fluorescence detection of pH and Cd2+. ► Limit of detection for Cd2+ was 12 nM. ► Experimental results confirmed high selectivity of this sensor. ► Perfect analytical performance was achieved in real samples.

Liposomes with superparamagnetic iron oxide nanoparticles embedded in membrane were prepared by the supercritical carbon dioxide (scCO2) method. The cargos can be released from liposomes by both triggered agents, temperature and alternating current electromagnetic field (AMF). The release mechanism was explained from the view of microstructure change investigated by fluorescence probe method. The contents could be repetitively released from liposomes controlled by switching on and off the AMF. The results indicated that the release from the liposomes was due to the magnetocaloric effect resulting in the liposome phase transition and the magnetic-impelled motions leading to the improved bilayer permeability, rather than the destruction of the liposome structure.Graphical abstractHighlights► Liposomes with hydrophobic magnetic nanoparticles in membrane were prepared. ► The release of cargo from magnetoliposomes can be controlled by thermal stimulation. ► The release of cargo from magnetoliposomes can be triggered by magnetic stimulation. ► Repetitive release proved the retained liposome structure during the release process. ► Hydrophobic magnetic nanoparticles affects the release property of magnetoliposomes.

Novel thermosensitive liposomes with embedded Au nanoparticles (AuNPs) in the liposome bilayer were prepared by a combination method of film build and supercritical CO2 incubation. These AuNPs–liposomes possess AuNPs that are embedded in the bilayer and a drug that is encapsulated in the central aqueous compartment. The AuNPs in the liposomes can strongly absorb light energy and efficiently convert the absorbed energy to heat. The localized heat induces a phase transition in the liposome bilayer and releases the drug. The drug release from the AuNPs–liposomes can be controlled by the irradiation time and AuNPs concentration in the AuNPs–liposomes at room temperature, where the AuNPs function as a nanoswitch for triggering drug release both spatially and temporally. The results suggest that drug release from the AuNPs–liposomes is due to a photothermic effect that induces phase transition of the liposomes rather than destruction of the liposome bilayer.

Magnetoliposomes, consisting of liposomes and magnetic nanoparticles (MNPs), have been tailored as very promising delivery vehicles in biotechnology and biomedicine applications. In this paper, liposomes with hydrophobic MNPs were prepared. The hydrophobic MNPs were successfully embedded in the lipid bilayer, which was proved by the results obtained from transmission electron microscope, atomic force microscope, differential scanning calorimetry and steady state fluorescence measurements. Moreover, systematic researches were carried out to investigate the effects of hydrophobic MNPs concentration on the morphology and microstructure of liposomes. The results show that the lipid bilayer was saturated with the hydrophobic MNPs when the mass ratio of MNPs to lipid reached 0.002.Graphical abstractHighlights► Liposomes with hydrophobic Fe3O4 nanoparticles in bilayer were prepared and studied. ► Saturation concentration of Fe3O4 in bilayer was confirmed by different methods. ► The embedded hydrophobic nanoparticles modify the microstructure of lipid bilayer. ► The embedded hydrophobic nanoparticles provide better membrane fluidity. ► The hydrophobic nanoparticles enlarge nonpolar domain and free volume in membrane.

At room temperature, the self-assembly of CdTe/ZnS quantum dots (QDs)/poly(N-isopropylmethacylamide-co- methylacrylic acid) [QDs/P(NIPAM–MAA)] hybrid microgels were achieved. The temperature-dependent swelling and shrinking behavior of polymer microgels played an important role in the photoluminescence (PL) changes of hybrid microgels. At 25 °C, polyethylenimine modified-QDs and P(NIPAM–MAA) microgels (at the swelling state) were combined by electrostatic attraction to form nanocompounds. At 45 °C, nanocompounds' shrinking triggered strong scattering centers, together with marked PL decrease. Almost whole reversible PL changes were observed between 25 °C and 45 °C after repeated heating-cooling cycles. In addition, the nanocompounds exhibited well monodisperse spheres and bright PL imaging, the average diameter was found to be approximately 300 nm.Graphical abstractHighlights► Water-soluble quantum dots encapsulated into thermosensitive microgels exhibited reversible luminescence behavior between 25 °C and 45 °C. ► TEM testified the acquirement of quantum dots/microgels nanocompounds. ► Luminescent mechanism was discussed. ► These nanocompounds were applied in fluorescence imaging.

Rhodamine 6G (R6G) and 3-mercaptopropionic acid (MPA) capped-CdTe quantum dots (QDs) were conjugated by electrostatic interactions in aqueous solution. The R6G-QDs conjugate was utilized as a photoluminescence (PL) ratiometric sensor for the detection of glutathione (GSH). In this method, intentional introduction of GSH destroyed the conjugation of R6G and QDs, and induced regular PL change of R6G-QDs conjugates due to the competitive chelation between GSH and MPA ligand on the surface of QDs. The ratio of PL intensity of R6G (IR6G) to that of QDs (IQDs) in this conjugate was near linear toward the concentration of GSH in the range from 0.05 to 80 μM, and corresponding regression equation showed a good linear coefficient of 0.9954. The limit of detection of 15 nM in this proposed method was about 40-fold lower than that of other QDs-based PL sensors. Interferential experiments testified that R6G-QDs conjugates-based ratiometric PL sensor of GSH showed high selectivity over other related thiols and amino acids. Real sample assays further verified perfect analysis performance of the PL sensor of GSH. In comparison with conventional analytical techniques for the measurement of GSH, this ratiometric PL sensor was facile, economic, highly sensitive and selective.Highlights► Rhodamine 6G-quantum dots conjugates were developed to be a ratiometric fluorescence sensor of glutathione. ► Interferential experiments and real samples assays verified the perfect analysis performance of the sensor. ► The sensor exhibited a much low limit of detection (15 nM).

A near-infrared-emitting CdTe/CdS core/shell quantum dots (QDs)-based photoluminescence (PL) sensor was designed and applied for highly selective and sensitive detection of Cd2+. This sensor was based on a PL “OFF–ON” mode. First, the addition of ammonium pyrrolidine dithiocarbamate (APDC) led to remarked PL quenching of QDs. Second, PL of APDC surface modified QDs (QDs-APDC) was gradually restored with the each increment of Cd2+ concentration. Experimental results showed that PL of QDs-APDC was near proportional upon the addition of Cd2+ in the range from 0.1 to 2 μM with a good correlation coefficient of 0.9989. The limit of detection of this proposed method was 6 nM. Interferential experiments confirmed that this sensor of Cd2+ was highly selective over other metal ions. To further investigate perfect analysis performance, this sensor was favorably utilized to determine Cd2+ in tap water, river water and liposome solutions.Highlights► A near-infrared-emitting quantum dots-based fluorescence sensor was developed to detect Cd2+. ► This sensor was based on a fluorescence “OFF–ON” mode. ► The limit of detection was 6 nM. ► Interferential experiments confirmed the high selectivity of this sensor.

Highly fluorescent silver nanoparticles (AgFNPs) have been prepared by microemulsion method and the sizes of AgFNPs were controlled by altering the molar ratio (ω) of water-to-surfactant in the water-in-oil microemulsion. The results were shown that the AgFNPs sizes increased with incremental molar ratio (ω) of water-to-surfactant. The AgFNPs have been characterized by transmission electron microscopy, dynamic light scattering, fluorescence and absorption spectroscopy, and fluorescence lifetime study. Study of the spectral characteristics was shown that the absorbance of AgFNPs increased significantly with the ω, and linear relationship between absorbance and the size of AgFNPs was observed. The increase of AgFNPs size caused a red shift of maximum absorption wavelength in the UV–Vis spectra, and the relationship between maximum absorption wavelength and AgFNPs size appeared linear dependence. The maximum fluorescence emission wavelength did not shift with the change of particles size, but the emission intensity increases with the ω. The results were shown that the other factors to affect the fluorescence properties of AgFNPs were the surface properties and microstructure, except the AgFNPs size. These surface properties depend upon the stabilizing agent, reactant concentration, and solvents and so on.

The coexistence curves (T, n), (T, Φ), and (T, Ψ) (n, Φ, and Ψ are the refractive index, volume fraction, and effective volume fraction, respectively) for the ionic liquid microemulsion systems of {polyoxyethylene tert-octylphenyl ether (T-X100) + 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) + cyclohexane} with various molar ratio (ω) of [bmim][BF4] to T-X100 have been determined by measuring refractive indices at a constant pressure in the critical region. The critical temperatures (Tc) and critical volume fraction (Φc) were obtained for the ionic liquid microemulsions. The critical exponents were deduced precisely from the coexistence curves within about 1 K below Tc and the values were consistent with the 3D Ising value.Graphical abstractThe critical exponents are consistent with the 3D Ising value in the critical region for ionic liquid microemulsion system.Highlights► The liquid-liquid coexistence curves of the ionic liquid microemulsion were determined in the critical region. ► The experimental results were analyzed to determine the critical exponent β and the critical amplitude B, and the anomalies of the diameters for different choices of order parameters. ► The IL microemulsions critical behavior belonged to the 3D-Ising universality class in a region sufficiently closed to the critical temperature.

A pH- and thermo-sensitive berberine hydrochloride liposome modified by the poly(N-isopropylacrylamide-co-methacrylic acid-co-octadecyl acrylate) was synthesized. The morphology and size were determined by atomic force microscope (AFM) and dynamic light scattering (DLS). The phase transition temperature (Tpm) and phase transition pH (pH*) of the copolymer–liposome were obtained by differential scanning calorimetry (DSC). The results indicate that the size of copolymer–liposome depends on the mass ratios of the copolymer to soya bean lecithin (SPC) and the solution pH value, and the size can reach a maximum value at phase transition pH (pH*). The Tpm and pH* were affected by the mass ratios of the copolymer to SPC and properties of the copolymer. The release of berberine hydrochloride (BH) from the copolymer–liposome was investigated and the maximum release of BH was caused at Tpm and pH* of the copolymer–liposome. The results illustrate that BH released from the liposome is due to the phase transition of the copolymer–liposome, where both Tpm and pH* were acted as switches of the phase transition, and both spacial and temporal releases can be carried out by adjusting the temperature, pH value and release time.Graphical abstractHighlights► A copolymer–liposome with both temperature and pH sensitive was synthesized. ► Phase transition temperature and pH of the copolymer–liposome were determined. ► Optimum drug release was at a point with both phase transition temperature and pH.

The critical behavior of an ionic liquid-in-oil (IL-O) microemulsion of 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] (IL), cyclohexane, and the nonionic surfactant polyoxyethylene tert-octylphenyl ether (T-X100) was studied for the first time. The coexistence curves of (T, n) and (T, Φ) (n and Φ are refractive index and volume fraction of the fraction of the volume of IL and T-X100 to the total volume of the system, respectively) for an IL-O microemulsion at constant pressure and a constant molar ratio (ω) of IL to T-X100 have been determined by measurements of the refractive index. The critical exponent β was deduced precisely from (T, n) and (T, Φ) coexistence curves. These values were 0.329 and 0.330, respectively, and were consistent with the 3D Ising exponent within experimental uncertainties. The refractive index (n) is a better choice of the concentration variable than the volume fraction (Φ) used for the construction of the order parameter to fit the Ising behavior.

A thermosensitive liposome with embedded AuNPs in a bilayer was prepared using supercritical CO2. The AuNPs-liposome can absorb a certain wavelength light, convert optical energy into heat, induce phase transition, and release drug. The results show that drug release from the liposome is due to the photothermic effects inducing phase transition of the liposome rather than destruction of the liposome structure.

A thermosensitive liposome with embedded AuNPs in a bilayer was prepared using supercritical CO2. The AuNPs-liposome can absorb a certain wavelength light, convert optical energy into heat, induce phase transition, and release drug. The results show that drug release from the liposome is due to the photothermic effects inducing phase transition of the liposome rather than destruction of the liposome structure.