Meng Cao

Bio: Meng Cao is an academic researcher from Shanghai University. The author has contributed to research in topics: Thin film & Sputter deposition. The author has an hindex of 12, co-authored 61 publications receiving 497 citations.

WO3 nanocrystals: Synthesis and application in highly sensitive detection of acetone

Abstract: WO3 nanocrystals have been prepared by a sol–gel route and characterized by X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy. The experimental results show that WO3 nanocrystals have a high crystallographic quality and a good dispersivity. The particles’ sizes are in the range of 25–100 nm. The fabricated WO3 nanocrystal-based sensors have an excellent sensitivity and selectivity to acetone, and display a rapid response and recovery characteristics. The developed sensors exhibit a detection limit down to 0.05 ppm at 300 °C, rendering a promising application in noninvasive diagnosis of diabetes. The response mechanism of the WO3 nanocrystal sensor to low concentration of acetone has been discussed based on the depletion layer model.

Recent advances in metal sulfides: from controlled fabrication to electrocatalytic, photocatalytic and photoelectrochemical water splitting and beyond

Abstract: In recent years, nanocrystals of metal sulfide materials have attracted scientific research interest for renewable energy applications due to the abundant choice of materials with easily tunable electronic, optical, physical and chemical properties. Metal sulfides are semiconducting compounds where sulfur is an anion associated with a metal cation; and the metal ions may be in mono-, bi- or multi-form. The diverse range of available metal sulfide materials offers a unique platform to construct a large number of potential materials that demonstrate exotic chemical, physical and electronic phenomena and novel functional properties and applications. To fully exploit the potential of these fascinating materials, scalable methods for the preparation of low-cost metal sulfides, heterostructures, and hybrids of high quality must be developed. This comprehensive review indicates approaches for the controlled fabrication of metal sulfides and subsequently delivers an overview of recent progress in tuning the chemical, physical, optical and nano- and micro-structural properties of metal sulfide nanocrystals using a range of material fabrication methods. For hydrogen energy production, three major approaches are discussed in detail: electrocatalytic hydrogen generation, powder photocatalytic hydrogen generation and photoelectrochemical water splitting. A variety of strategies such as structural tuning, composition control, doping, hybrid structures, heterostructures, defect control, temperature effects and porosity effects on metal sulfide nanocrystals are discussed and how they are exploited to enhance performance and develop future energy materials. From this literature survey, energy conversion currently relies on a limited range of metal sulfides and their composites, and several metal sulfides are immature in terms of their dissolution, photocorrosion and long-term durability in electrolytes during water splitting. Future research directions for innovative metal sulfides should be closely allied to energy and environmental issues, along with their advanced characterization, and developing new classes of metal sulfide materials with well-defined fabrication methods.

Thin-Wall Assembled SnO2 Fibers Functionalized by Catalytic Pt Nanoparticles and their Superior Exhaled-Breath-Sensing Properties for the Diagnosis of Diabetes

Abstract: Hierarchical SnO 2 fi bers assembled from wrinkled thin tubes are synthesized by controlling the microphase separation between tin precursors and polymers, by varying fl ow rates during electrospinning and a subsequent heat treatment The inner and outer SnO 2 tubes have a number of elongated open pores ranging from 10 nm to 500 nm in length along the fi ber direction, enabling fast transport of gas molecules to the entire thin-walled sensing layers These features admit exhaled gases such as acetone and toluene, which are markers used for the diagnosis of diabetes and lung cancer The open tubular structures facilitated the uniform coating of catalytic Pt nanoparticles onto the inner SnO 2 layers Highly porous SnO 2 fi bers synthesized at a high fl ow rate show fi ve-fold higher acetone responses than densely packed SnO 2 fi bers synthesized at a low fl ow rate Interestingly, thin-wall assembled SnO 2 fi bers functionalized by Pt particles exhibit a dramatically shortened gas response time compared to that of un-doped SnO 2 fi bers, even at low acetone concentrations Moreover, Pt-decorated SnO 2 fi bers signifi cantly enhance toluene response These results demonstrate the novel and practical feasibility of thin-wall assembled metal oxide based breath sensors for the accurate diagnosis of diabetes and potential detection of lung cancer

Zinc oxide based dye-sensitized solar cells: A review

Abstract: Zinc oxide (ZnO) is the closest alternative to TiO2 as the semiconductor material in a dye-sensitized solar cell (DSSC). This is to be attributed to the facts that both TiO2 and ZnO have same electron affinities and almost the same band gap energies, and ZnO has much higher electron diffusivity than TiO2, a high electron mobility, a large excitation binding energy, is available at low-cost, and stable against photo-corrosion. The article provides a broad survey of ZnO based DSSCs, and highlights the potential of utilizing a ZnO photoanode in the place of a TiO2 photoanode in a DSSC. The merits of a ZnO photoanode, over against those of a TiO2 photoanode, are discussed in detail, associated main problems are mentioned, and their solutions are suggested. Parameters to improve the performance of a DSSC are revealed and solutions to optimize them are suggested. Discussions are made on ZnO based flexible, quasi-solid state, and solid state DSSCs. The advantages and disadvantages of ZnO as semiconductor material in DSSCs are weighed. All architectures reported till date are cited, and the techniques used to achieve such hierarchical structures are mentioned. A thorough discussion is made on the dyes used for ZnO based DSSCs. Organic dyes and metal-free dyes are found to be most suitable for such DSSCs. Optimum particle size of ZnO, its stability, its suitable facet for the application in a DSSC, and the best redox couple for a ZnO based DSSC are discussed with evidences. Great emphasis is given on ZnO films that are doped with various materials. The review also discusses miscellaneous works on ZnO based DSSCs. A hitherto never discussed concept of usage of MOFs in a ZnO based DSSC concludes the review.

Natural dyes for dye sensitized solar cell: A review

Abstract: Dye sensitized solar cell converts visible light into electricity using sensitization of the cell. Performances of dye sensitized solar cells are mainly based on dye used as a sensitizer. Now a days study of dyes extracted from natural resources is the main concern for researchers. Application of natural dyes is a promising development in the field of this technology. Natural dyes are cutting down high cost of metal complex sensitizers and also replacing expensive chemical synthesis process through simple extraction process. Natural dyes are abundant, easily extractable, safe material causes no environment threat. These can be extracted from flowers petals, leaves, roots and barks in the form of anthocyanin, carotenoid, flavonoid and chlorophyll pigments. This review discusses development of natural dyes and their effect on various performance parameters of dye sensitized solar cell.

Metal oxides nanoparticles via sol–gel method: a review on synthesis, characterization and applications

Abstract: Metal oxide nanoparticles (MONPs) have enormous applications such as in optical devices, purification systems, biomedical systems, photocatalysis, photovoltaics etc. In this review, we have explored a stable and efficient synthesis protocol of particularly four MONPs: titanium dioxide (TiO2), tin oxide (SnO2), tungsten oxide (WO3) and zinc oxide (ZnO) for getting desired chemical composition, nanostructure, and surface properties. The selection of an efficient synthesis process is a key factor that significantly influences the efficacy of the MONPs. The chemical synthesis of nanoparticles (NPs) via sol–gel route is an effective method to produce high-quality MONPs in comparison to other physical and chemical methods. Sol–gel synthesis is one of the simple, fastest and economically less expensive method, and has its own advantages like low processing temperature, homogeneity of the produced material and formation of the complex structures or composite materials. We believe that this detailed review will provide an insight into sol–gel synthesis of MONPs along with their characterization and diverse applications.