Yuming Dong

Dual responsive enzyme mimicking activity of AgX (X=Cl, Br, I) nanoparticles and its application for cancer cell detection.

Chitosan (CS) modified silver halide (AgX, X=Cl, Br, I) (CS-AgX) nanoparticles (NPs) were found to possess dual responsive enzyme mimetic activities. In the presence of H2O2, they were able to oxidize various colorimertic dyes, namely, peroxidase-like activity. Upon photoactivation, CS-AgX NPs could also oxidize the typical substrates in the absence of H2O2. Taking CS-AgI as an example, it was found that the photostimulated enzyme mimetics of CS-AgI NPs showed several unprecedented advantages over natural peroxidase or other existing alternatives based on nanomaterials, such as excellent enzyme-like activity over a broad pH range (3.0-7.0), the independence of hydrogen peroxide on activity, the easily regulated activity by light irradiation, and the good reutilization without significant loss of catalytic activity. The mechanism of the dual responsive enzyme-like activity of CS-AgI was investigated. On the basis of these findings, the photoactivated CS-AgI was designed to develop a facile, cheap, rapid, and highly sensitive colorimetric assay to detect cancer cells. The detection limit of the method for MDA-MB-231 was estimated to be as low as 100 cells, which was much lower than that reported by the method using peroxidase mimetics based on nanomaterials. We believe that CS-AgX NPs with dual responsive enzyme-mimicking activity, especially the excellent photostimulated enzyme-like activity, may find widely potential applications in biosensors.

Insight into the Crucial Factors for Photochemical Deposition of Cobalt Cocatalysts on g-C3N4 Photocatalysts

Photochemical preparation of inexpensive hydrogen evolution cocatalysts is of great significance and is challenging. Currently, the crucial factors in the photochemical preparation of nonnoble metals are still unknown. In this work, taking Co/g-C3N4 composite photocatalysts as a case, complexing agents and sacrificial agents were found to be the crucial factors for the photochemical deposition process. Cobalt was supported on the electron outlet points of g-C3N4 for 1 h, and the ratio of Co in the Co/g-C3N4 composite photocatalyst can be regulated by changing the irradiation time of the preparation process. The optimized hydrogen evolution rate of Co/g-C3N4 was about 11.48 μmol h-1, which was 75 times more than pure g-C3N4. The photocatalytic H2 evolution rate was stable after 48 h. The mechanism for the high activity of Co/g-C3N4 composites was explored by surface photovoltage spectra and photoluminescence spectra. Co effectively promoted the separation of the photogenerated electrons and holes of g-C3N4 and improved the H2 production rate.

Enzyme-Initiated Quinone-Chitosan Conjugation Chemistry: Toward A General in Situ Strategy for High-Throughput Photoelectrochemical Enzymatic Bioanalysis

Herein we report a general and novel strategy for high-throughput photoelectrochemical (PEC) enzymatic bioanalysis on the basis of enzyme-initiated quinone-chitosan conjugation chemistry (QCCC). Specifically, the strategy was illustrated by using a model quinones-generating oxidase of tyrosinase (Tyr) to catalytically produce 1,2-bezoquinone or its derivative, which can easily and selectively be conjugated onto the surface of the chitosan deposited PbS/NiO/FTO photocathode via the QCCC. Upon illumination, the covalently attached quinones could act as electron acceptors of PbS quantum dots (QDs), improving the photocurrent generation and thus allowing the elegant probing of Tyr activity. Enzyme cascades, such as alkaline phosphatase (ALP)/Tyr and β-galactosidase (Gal)/Tyr, were further introduced into the system for the successful probing of the corresponding targets. This work features not only the first use of QCCC in PEC bioanalysis but also the separation of enzymatic reaction from the photoelectrode as well as the direct signal recording in a split-type protocol, which enables quite convenient and high-throughput detection as compared to previous formats. More importantly, by using numerous other oxidoreductases that involve quinones as reactants/products, this protocol could serve as a common basis for the development of a new class of QCCC-based PEC enzymatic bioanalysis and further extended for general enzyme-labeled PEC bioanalysis of versatile targets.

Synthesis of Hydrotalcite-like Compounds Intercalated by 12- Phosphorus Tungsten Heteropoly Acid and Catalytic Performance on the Epoxidation of Fatty Acid Methyl Esters

A kind of effective hydrotalcite-like catalysts which can be used in the epoxidation of fatty acid methyl esters were exploited in this work. The hydrotalcite-like compounds were synthesized by using the coprecipitation method, and then a novel pillared-hydrotalcite was obtained through ion-exchange method. Then, the catalyst activity was tested by epoxidation of fatty acid methyl esters without carboxylic acid, and the results indicate that pillared-hydrotalcite shows better catalytic performance. The effects of reaction time, temperature and catalyst reusability on the epoxidation of fatty acid methyl esters were discussed in detail. The conversion and selectivity of epoxy products reach 56.1% and 59.4% respectively at 60 ℃ for 16 h. After recycling 4 times, the recycle utility rate was still over 90%. Finally, the mechanism of interaction be- tween the catalyst and oxidant was investigated.

ITO nanoparticle film as a hole-selective layer for PbS-sensitized photocathodes

Photocathodes sensitized by photoactive semiconductors are of great significance for photoelectrochemical hydrogen evolution and tandem solar cells, yet their development is hindered by the scarcity of appropriate materials to serve as a hole-selective layer. In this work, we report a novel photocathode employing PbS as the photoactive material and tin-doped indium oxide (ITO) as the hole-selective layer. The optimized electrode showed a photocurrent of −75 μA cm−2 under light illumination at −0.222 V vs. Ag/AgCl with operational activity for 9 hours. The key factors for hole transfer were investigated. These results showed ITO to be a promising hole-transfer material for photoelectrochemical photocathodes.

MoO2 Formed on Mesoporous Graphene Oxide: Efficient and Stable Catalyst for Epoxidation of Olefins

A novel mesoporous MoO2 composite supported on graphene oxide (m-MoO2/GO) has been designed and applied as an efficient epoxidation catalyst. The m-MoO2/GO composite was characterised by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, Brunauer–Emmet–Teller surface area analysis, field emission scanning electron microscopy, and transmission electron microscopy. Compared with pure mesoporous MoO2 (m-MoO2) and amorphous MoO2-graphene oxide (a-MoO2/GO), m-MoO2/GO exhibits the best catalytic activity. The conversion and selectivity for cyclooctene are both over 99 % in 6 h. Remarkably, the mesoporous structure in m-MoO2/GO which derives from SiO2 nanospheres endows the catalyst better catalytic performance for long chain olefins: the conversion of methyl oleate can be as high as 82 %. Such a robust catalyst can be easily recycled and reused five times without significant loss of catalytic activity. This novel catalyst is promising in the synthesis of epoxides with a long carbon chain or large ring size.