Author
Wencai Yi
Other affiliations: California State University, Northridge, Jilin University
Bio: Wencai Yi is an academic researcher from Qufu Normal University. The author has contributed to research in topics: Raman spectroscopy & Materials science. The author has an hindex of 16, co-authored 58 publications receiving 790 citations. Previous affiliations of Wencai Yi include California State University, Northridge & Jilin University.
Papers
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TL;DR: In this article, the authors used molybdenum dioxide as a SERS material, showing high enhancement factors and stability to oxidation even at high temperatures, which is the best among the metal oxides and even reaches or approaches to Au/Ag.
Abstract: Compared with noble metals, semiconductors with surface plasmon resonance effect are another type of SERS substrate materials. The main obstacles so far are that the semiconducting materials are often unstable and easy to be further oxidized or decomposed by laser irradiating or contacting with corrosive substances. Here, we report that metallic MoO2 can be used as a SERS substrate to detect trace amounts of highly risk chemicals including bisphenol A (BPA), dichloropheno (DCP), pentachlorophenol (PCP) and so on. The minimum detectable concentration was 10−7 M and the maximum enhancement factor is up to 3.75 × 106. To the best of our knowledge, it may be the best among the metal oxides and even reaches or approaches to Au/Ag. The MoO2 shows an unexpected high oxidation resistance, which can even withstand 300 °C in air without further oxidation. The MoO2 material also can resist long etching of strong acid and alkali. Semiconducting materials are potential SERS substrates as alternatives to noble metals, but often suffer from poor stabilities and sensitivities. Here, the authors use molybdenum dioxide as a SERS material, showing high enhancement factors and stability to oxidation even at high temperatures.
211 citations
TL;DR: Kinetics simulations have been performed to study the importance of these reactions in the reduction of atmospheric SO2 and give a new insight on how the pre-existing aerosols catalyze the hydrolysis of SO2, leading to the formation and growth of new particles.
Abstract: The deposition and hydrolysis reaction of SO2 + H2O in small clusters of sulfuric acid and water are studied by theoretical calculations of the molecular clusters SO2–(H2SO4)n–(H2O)m (m = 1,2; n = 1,2). Sulfuric acid exhibits a dramatic catalytic effect on the hydrolysis reaction of SO2 as it lowers the energy barrier by over 20 kcal/mol. The reaction with monohydrated sulfuric acid (SO2 + H2O + H2SO4 – H2O) has the lowest energy barrier of 3.83 kcal/mol, in which the cluster H2SO4–(H2O)2 forms initially at the entrance channel. The energy barriers for the three hydrolysis reactions are in the order SO2 + (H2SO4)–H2O > SO2 + (H2SO4)2–H2O > SO2 + H2SO4–H2O. Furthermore, sulfurous acid is more strongly bonded to the hydrated sulfuric acid (or dimer) clusters than the corresponding reactant (monohydrated SO2). Consequently, sulfuric acid promotes the hydrolysis of SO2 both kinetically and thermodynamically. Kinetics simulations have been performed to study the importance of these reactions in the reduction o...
63 citations
TL;DR: A Linux-based command-line toolkit was developed to assist VASP users to perform various types of calculations, such as structure optimization, single point energy, work function, electronic structure simulations, mechanical and optical property calculations.
58 citations
TL;DR: It is reported that plasmonic MoO2 nanospheres can be used as a highly sensitive and stable semiconducting-substrate material for surface-enhanced Raman scattering (SERS).
Abstract: Semiconductor-based surface-enhanced Raman spectroscopy is getting more and more attention because of its great price advantage. One of the biggest obstacles to the large-scale application of it is the poor stability. Here, we report that plasmonic MoO2 nanospheres can be used as a highly sensitive and stable semiconducting-substrate material for surface-enhanced Raman scattering (SERS). By using the MoO2 nanospheres as Raman substrates, a series of typical compounds with high attention can be accurately detected. This new non-noble metal substrate material shows a very high detection limit of 10–8 M, and exhibits great near-field enhancement with one of the highest enhancement factor of 4.8 × 106 reported to date. More importantly, the oxide with intermediate valence displays unexpected ultrahigh stability, which can withstand the corrosion of strong acid and strong alkali as well as 150 °C high temperature oxidation in air. Moreover, the accurate detection of multicomponent samples was also successful o...
58 citations
TL;DR: In this article, a series of planar boron allotropes with honeycomb topology was proposed and their band structures exhibited Dirac cones at the K point, the same as graphene.
Abstract: We propose a series of planar boron allotropes with honeycomb topology and demonstrate that their band structures exhibit Dirac cones at the K point, the same as graphene. In particular, the Dirac point of one honeycomb boron sheet locates precisely on the Fermi level, rendering it as a topologically equivalent material to graphene. Its Fermi velocity (vf) is 6.05 × 105 m/s, close to that of graphene. Although the freestanding honeycomb B allotropes are higher in energy than α-sheet, our calculations show that a metal substrate can greatly stabilize these new allotropes. They are actually more stable than α-sheet sheet on the Ag(111) surface. Furthermore, we find that the honeycomb borons form low-energy nanoribbons that may open gaps or exhibit strong ferromagnetism at the two edges in contrast to the antiferromagnetic coupling of the graphene nanoribbon edges.
56 citations
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TL;DR: VASPKIT as mentioned in this paper is a command-line program that aims at providing a robust and user-friendly interface to perform high-throughput analysis of a variety of material properties from the raw data produced by the VASP code.
1,357 citations
TL;DR: This review organizes and introduces several common gas sensing mechanisms of metal oxide semiconductors in detail and classifies them into two categories, the scope and relationship of these mechanisms are clarified and some perspectives for future investigations on the gas sensing mechanism are discussed.
Abstract: In recent years, gas sensors have been increasingly used in industrial production and daily life. Metal oxide semiconductor gas sensing materials are favoured for their outstanding physical and chemical properties, low cost and simple preparation methods. However, the gas sensing mechanisms of metal oxide semiconductors have not been considered by researchers, resulting in omissions and errors in the interpretation of gas sensing mechanisms in many articles. This review organizes and introduces several common gas sensing mechanisms of metal oxide semiconductors in detail and classifies them into two categories. The scope and relationship of these mechanisms are clarified. In addition, this review selects four strategies for enhancing the gas sensing properties of metal oxide semiconductors and analyses the gas sensing mechanisms to highlight the importance of the gas sensing mechanism. Finally, some perspectives for future investigations on the gas sensing mechanisms of metal oxide semiconductors are discussed as well.
488 citations
TL;DR: The flexible SERS substrates with low‐cost, batch‐fabrication, and easy‐to‐operate characteristics can be integrated into portable Raman spectroscopes for point‐of‐care diagnostics, which are conceivable to penetrate global markets and households as next‐generation wearable sensors in the near future.
Abstract: Surface-enhanced Raman scattering (SERS) spectroscopy provides a noninvasive and highly sensitive route for fingerprint and label-free detection of a wide range of molecules. Recently, flexible SERS has attracted increasingly tremendous research interest due to its unique advantages compared to rigid substrate-based SERS. Here, the latest advances in flexible substrate-based SERS diagnostic devices are investigated in-depth. First, the intriguing prospect of point-of-care diagnostics is briefly described, followed by an introduction to the cutting-edge SERS technique. Then, the focus is moved from conventional rigid substrate-based SERS to the emerging flexible SERS technique. The main part of this report highlights the recent three categories of flexible SERS substrates, including actively tunable SERS, swab-sampling strategy, and the in situ SERS detection approach. Furthermore, other promising means of flexible SERS are also introduced. The flexible SERS substrates with low-cost, batch-fabrication, and easy-to-operate characteristics can be integrated into portable Raman spectroscopes for point-of-care diagnostics, which are conceivable to penetrate global markets and households as next-generation wearable sensors in the near future.
348 citations
TL;DR: Z-scheme composite represents an ideal system for photocatalytic hydrogen evolution, but the charge transfer mechanism is still ambiguous, and how to design and construct such a system is a big challenge as mentioned in this paper.
319 citations
TL;DR: This review article encompasses some recent advances in the facet engineering that has been performed to control the surface of mono‐component semiconductor systems and to design the surface and interface structures of multi‐component heterostructures toward photocatalytic applications.
Abstract: The facet-engineered surface and interface design for photocatalytic materials has been proven as a versatile approach to enhance their photocatalytic performance. This review article encompasses some recent advances in the facet engineering that has been performed to control the surface of mono-component semiconductor systems and to design the surface and interface structures of multi-component heterostructures toward photocatalytic applications. The review begins with some key points which should receive attention in the facet engineering on photocatalytic materials. We then discuss the synthetic approaches to achieve the facet control associated with the surface and interface design. In the following section, the facet-engineered surface design on mono-component photocatalytic materials is introduced, which forms a basis for the discussion on more complex systems. Subsequently, we elucidate the facet-engineered surface and interface design of multi-component photocatalytic materials. Finally, the existing challenges and future prospects are discussed.
289 citations