Spiropyran-modified silicon quantum dots (Si QDs) were successfully fabricated through covalently linking the aminated Si QDs and spiropyrans. In comparison with Si QDs, the fluorescence emission peaks of the Si QDs in the spiropyran-modified Si QDs always locate at 525 nm irrespective of the excitation wavelengths. The spiropyran-modified Si QDs showed reversible photoluminescence. Blue-green fluorescence of the spiropyran-modified Si QDs could be gradually switched off, and red fluorescence could be gradually switched on with UV irradiation. The process could be reversible with visible light irradiation. The reversibly switchable photoluminescence of the spiropyran-modified Si QDs using UV and visible light irradiation could also be multiply repeated with good stability. Therefore, the spiropyran-modified Si QDs could be a promising candidate in many potential application areas such as photo-switch, data storage, and biolabeling and bioimaging.

Silicon quantum dots (Si QDs) were synthesized by a facile one-step synthesis that involved etching silicon powder through a hydrothermal method. The Si QDs, without any surface modification, maintained good water dispersibility, strong photoluminescence and high pH stability, and can be used as a sensor to detect Cu2+.

A kind of photoswitchable nanoparticles which are the fluorescent carbon nanoparticles grafted with the copolymers of styrene and spiropyran (f-CNP-g-poly(St-co-SP) is reported. The f-CNP-g-poly(St-co-SP) not only feature the reversibly photoswitchable fluorescence, but also have good processability. Their fluorescence could be reversibly switched between blue-green and red by using ultraviolet/visible light irradiation. Furthermore, they could be readily processed into nanofibers with reversibly photoswitchable fluorescence by electrospinning. They can be potentially applied in fabricating microdevice, optical switching, information storage, anti-counterfeiting as well as biological imaging.

Fluorescent carbon nanoparticles (f-CNPs) were successfully grafted with polystyrene by employing a “grafting from” method via reversible addition-fragmentation chain transfer polymerization (RAFT). The detailed polymerization kinetic studies showed that the grafting polystyrene polymerization from the f-CNPs surface via RAFT was living-controlled. The synthesized f-CNP-g-PSt nanocomposites with different grating lengths via RAFT could fluoresce like f-CNPs. At the same time, the synthesized f-CNP-g-PSt nanocomposites could be easily processed into fibers by electrospinning. The fibers could still fluoresce at the appropriate excitation wavelength. The f-CNP-g-PSt nanocomposites synthesized via RAFT feature good processability may be applied as luminescent plastic.

An innovative auto-catalytic method was proposed to synthesize phytosterol esters from phytosterols and long-chain fatty acids without adding any catalyst and solvent. The effects of reaction temperature, molar ratio of oleic acid/phytosterols, reaction time and carbon-chain length of the fatty acids on the reaction were investigated. The results showed that the conversion, the yield and the selectivity of the reaction were increased with the increase in reaction temperature, molar ratio and a decrease in the length of carbon chains of fatty acids. The selectivity was decreased on prolonging the reaction time. A high conversion (99.1%) with a high yield (94.9%) and selectivity (95.8%) was achieved under a molar ratio of oleic acid/phytosterols of 3:1, a reaction temperature of 220 °C and reaction time of 4 h. The properties of the phytosterol oleic esters by autocatalysis conformed to the quality indices of phytosterol esters from the China Ministry of Health and were superior to the commercial product. The kinetics suggested that the reaction order was 2 and the reaction activation energy was 58.75 kJ mol−1. The auto-catalytic process, omitting the separation step for catalysts and solvents, could be considered as a promising process to synthesize phytosterol esters.

Fluorescent carbon nanoparticles (CNPs) with diameters of about 3 nm which can emit blue-green light were synthesized through the hydrothermal carbonization of ethylenediaminetetraacetic acid disodium salt (EDTA·2Na). Then, the CNPs were functionalized with spiropyrans to obtain the spiropyran-functionalized CNPs. The emission of the spiropyran-functionalized CNPs centered at 510 nm could be switched off, while being turned on at 650 nm via energy transfer after UV light irradiation. The process could be reversed by using visible light irradiation. The optical switching of the fluorescence was repeated 10 times without apparent “fatigue”, showing excellent photoreversibility and high stability. Spiropyran-functionalized CNPs may find potential applications in biological imaging and labeling, reversible data storage/erasing, as well as individual light-dependent nanoscale devices.

The deactivation and in situ regeneration of anion exchange resin (D261) used as a catalyst in the continuous transesterification of soybean oil with methanol for biodiesel production were studied in a fixed-bed reactor. The chemical and physical structures of the resins were investigated by means of X-ray photoelectron spectrometer (XPS), N2 adsorption/desorption isotherms, and scanning electron microscope (SEM). The results showed that biodiesel conversion was over 90% within the run time of 4 h but rapidly declined to 23.7% after 8 h. The fouling of organic substances (triglyceride and glycerol) covered on the resin was the main reason leading to the decrease in the biodiesel conversion. The fouling extent on the resin was related to the resin position in the fixed bed. The largest activity loss of the resin occurred at the bottom of the fixed bed. The leakage of OH– groups from the resins, independent of the resin height in the bed, also resulted to the decline of the resin activity. An in situ regeneration method was put forward. The resin regenerated can be restored to the original catalytic activity to perform continuous transesterification for biodiesel production.

Poly(styrene sulfonic acid) (PSSA)/Poly(vinyl alcohol) (PVA) blend membranes prepared by the solution casting were employed as heterogeneous acid catalysts for biodiesel production from acidic oil obtained from waste cooking oil (WCO). The membranes were annealed at different temperature in order to enhance their stability. The structure and properties of the membranes were investigated by means of Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), X-ray diffraction (XRD). It is found that the crosslinking structure among PVA and PSSA chains formed when the thermal treatment temperature was higher than 80 °C. The retention of PSSA in the blend membranes in the methanol/water solvent was markedly increased from 50% to 85% with the increase of the annealing temperature from room temperature (for the untreated membrane) to 150 °C due to the formation of the crosslinking structure. The results of esterification of acidic oil show that the conversion was slightly improve with the PVA content in the membrane at a fixed PSSA content. The thickness of the catalytic membrane had no significant effect on the conversion in the end. The membrane annealed at 120 °C exhibited the best catalytic performance among the membranes, with a stable conversion of 80% with the runs.

The highly ordered porous films were fabricated from the solution of polystyrene with one carboxyl terminal group in carbon disulfur in a chamber with a water bath. It is found that the pore size can be readily controlled by changing the temperature of water bath. The pore size increases with an increase in the water-bath temperature in a given range. And the porous film from the “dilute” solution can be readily formed even at a low relative humidity (RH), while the porous film from the “concentrated” solution can be fabricated only at a rather high RH. The regularity of porous film becomes better at the higher RH and higher concentration. It suggests that there exists a synergetic effect of solution concentration and RH on the formation of porous film. These phenomena are explained by the slow evaporation rate of the solvent under the conditions.

Fluorescent carbon nanoparticles (CNPs) with diameters of about 3 nm which can emit blue-green light were synthesized through the hydrothermal carbonization of ethylenediaminetetraacetic acid disodium salt (EDTA·2Na). Then, the CNPs were functionalized with spiropyrans to obtain the spiropyran-functionalized CNPs. The emission of the spiropyran-functionalized CNPs centered at 510 nm could be switched off, while being turned on at 650 nm via energy transfer after UV light irradiation. The process could be reversed by using visible light irradiation. The optical switching of the fluorescence was repeated 10 times without apparent “fatigue”, showing excellent photoreversibility and high stability. Spiropyran-functionalized CNPs may find potential applications in biological imaging and labeling, reversible data storage/erasing, as well as individual light-dependent nanoscale devices.