Xinnian Xia

Photo-responsive reversible micelles based on azobenzene-modified poly(carbonate)s via azide–alkyne click chemistry

Photo-induced reversible amphipathic copolymer PMPC-azo was click conjugated by connecting amphiphilic poly(ethylene glycol)-modified poly(carbonate)s (PEG-b-poly(MPC)) and azide-functional trifluoromethoxy-azobenzene (azo-N3). The resulting copolymer self-assembled into spherical micelles with a hydrophobic azo core stabilized by a hydrophilic PEG corona in aqueous solution. As characterized by time-resolved UV-vis spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM), these micelles showed reversible self-assembly and disassembly in aqueous solution under alternating UV and visible light irradiation. The model drug Nile Red (NR) was then successfully encapsulated into the micelles. Light-controlled release and re-encapsulation behaviors were demonstrated by fluorescence spectroscopy. The cell cytotoxicity of PMPC-azo micelles was also evidenced by MTT assay. This study provides a convenient method to construct smart nanocarriers for controlled release and re-encapsulation of hydrophobic drugs.

Green synthesis of bisphenol F over 12-phosphotungstic acid supported on acid-activated palygorskite

In this study, acid-activated palygorskite (Pa) with tunable surface acidity was obtained by simple acidic treatment of raw clay. The new catalysts with 5–30 wt% 12-phosphotungstic acid (H3O40PW12·xH2O, PTA) were then readily prepared by the wet impregnation method. Their characteristic features were systematically investigated by various means including energy-dispersive X-ray (EDX), X-ray diffraction (XRD), N2 adsorption/desorption isotherms, Fourier-transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA), as well by comparison with Pa, PTA and H-Beta zeolite. The high activities of these catalysts promoted phenol to undergo hydroxyalkylation, resulting in an interesting bisphenol F (BPF) product. Among these solid acid catalysts, 10% PTA/Pa was chosen as the most suitable catalyst giving an 87% yield and 96% selectivity under mild conditions (phenol/formaldehyde mole ratio of 15 : 1; T = 343 K; catalyst concentration of 0.006 g g−1; 40 min). The surface acid strength and acidic type were characterized by ammonia temperature programmed desorption of NH3 (NH3-TPD), and FT-IR of pyridine adsorption (Py-IR). It was found that the catalytic activity could be further enhanced by impregnating PTA onto Pa due to the enhanced acid strength and the redistribution of Bronsted and Lewis acid sites. Besides, a more appropriate combination of Bronsted and Lewis acid sites was essential to achieve the highest BPF yield. Recycle experiments were conducted and a plausible mechanistic pathway was proposed according to our observations and findings.

Hollow Microsphere TiO2/ZnO p–n Heterojuction with High Photocatalytic Performance for 2,4-Dinitropheno Mineralization

A unique hollow microsphere TiO2/ZnO p–n heterojuction was successfully fabricated via a one-step hydrothermal method for degradation of 2,4-Dinitrophenol. The enhancement of mineralization of 2,4-dinitrophenol (2,4-DNP) via photocatalytic degradation of TiO2/ZnO p–n heterojuction was investigated. The 2,4-DNP was degraded completely by TiO2/ZnO, and 78% of the total organic carbon (TOC) was removed which is greatly superior to that on the controlled TiO2, ZnO with 53%, 45%, respectively. A schematic diagram of photocatalytic oxidation mechanism of 2,4-DNP was also presented by ⋅OH radical detection. The oxidation of 2,4-DNP and the intermediate productions was based on the hydroxyl (OH) with a high oxidation potential of 2.8V. Moreover, the excellent stability and reliability of the TiO2/ZnO composite hollow microsphere photocatalyst demonstrated its promising application for removal of organic pollutant from water.

Hydroxyalkylation of phenol to bisphenol F over Al-pillared clay

Hydroxyalkylation of phenol to bisphenol F over the intercalation of aluminum hydroxy oligomeric into layered montmorillonite K10 was investigated. A remarkably high product yield (89.2%) and selectivity to bisphenol F (92.7%) has been achieved at a 110 °C reaction temperature and reaction time of 80 min with a Al-MMT(6) catalyst. A series of catalysts were prepared and characterized by FT-IR, XRD, BET, NH3-TPD and Py-IR. Characterization results showed that the catalytic performance of these catalysts depended on weak and moderate acidity and the textural properties (specific surface areas). The effect of the catalyst calcination temperature to this reaction was also studied. Moreover, the influences of various reaction parameters like mole ratio, catalyst concentration, reaction temperature and reaction time on the product yield and selectivity to bisphenol F were investigated. Finally, the reusability of the catalyst was studied and a plausible mechanistic pathway was proposed.

Polycarbonate-based core-crosslinked redox-responsive nanoparticles for targeted delivery of anticancer drug

We reported a facile and efficient strategy for the construction of polycarbonate-based core-crosslinked redox-responsive nanoparticles (CC-RRNs), which can efficiently regulate the drug loading content and redox-responsive drug release. A series of CC-RRNs for delivery of doxorubicin (DOX) were synthesized by the click reaction between alkyne-bearing amphiphilic block copolymer PEG-b-poly(MPC)n (PMPC) and azide-terminated α-lipoic acid derivative (LA) and 6-bromohexanoic acid derivative (AHE) at different ratios, followed by introduction of crosslinked networks under a catalytic amount of dithiothreitol (DTT). Dynamic light scattering (DLS) experiments showed that the CC-RRNs presented more excellent stability over non-crosslinked unresponsive nanoparticles (NC-URNs) under physiological conditions. Interestingly, the DOX loading content of nanoparticles (NPs) increased as the proportion of LA moieties increased, and the maximum value was up to 20.0 ± 0.6%, close to the theoretical value of 23.1%. The in vitro redox-responsive release of DOX and MTT assays confirmed that the ratio of LA-to-AHE of PMPC-based polymers not only determined the ultimate drug release of DOX-loaded CC-RRNs in a reductive environment, but also dominated the cytotoxicity towards HepG2 cells. Confocal laser scanning microscopy (CLMS) and flow cytometry further proved the enhancement of cellular uptake and tumor accumulation. This facile strategy overcomes tedious fabrication procedures for drug nanocarriers, offers an opportunity for regulating the functionality of NPs, and thus paves the pathway for scale-up production of biodegradable drug carriers with biocompatibility, stability and targetability.

Fe 1-x Zn x S ternary solid solution as an efficient Fenton-like catalyst for ultrafast degradation of phenol

Heterogeneous Fenton-like system has been proved to be an promising alternative to Fenton system due to its easy separation. However, its a challenge to design heterogeneous Fenton-like catalysts with high activity and great durability. Here, ternary solid solution Fe1-xZnxS were prepared via hydrothermal synthesis as heterogeneous Fenton-like catalysts. The Fe0.7Zn0.3S sample exhibited state of the art activity for yielding OH by H2O2 decomposition, and the ultrafast degradation of phenol was achieved in 4 min at initial acidic condition under room temperature. The phenol degradation rate constant of Fe0.7Zn0.3S was 99 and 70 times of ZnS and FeS, respectively. Further, we show that the unique structural configuration of iron atoms, the formation of FeS2-pyrite with (200) plane, are responsible for the excellent activity. The intermediate products were identified by LC-MS and a possible pathway was accordingly proposed to elucidate the mechanism of phenol degradation by OH. Overall, this work provides an idea for the rational design of the relevant heterogeneous Fenton-like catalysts.