Metastable materials have received extensive attention due to their unique physical and chemical properties which are different from those of the thermodynamically stable phase. However, the variety of reported metastable materials is still very limited owing to difficulties in the effective synthesis of pure metastable materials because they can easily transform into the corresponding stable phases. Therefore, it is crucial and a great challenge to explore new metastable materials with novel and fascinating functions. In this study, hierarchically porous metastable β-Ag2WO4 hollow nanospheres with a diameter of 50-500 nm were prepared for the first time by a facile precipitation reaction between AgNO3 and Na2WO4 in the presence of poly(methacrylic acid) (PMAA). It was found that the PMAA not only provided a spherical soft template to induce the formation of hollow nanospheres but also worked as an inhibitor to prevent the phase transformation from thermodynamically unstable β-Ag2WO4 to stable α-Ag2WO4 phase. The resultant metastable β-Ag2WO4 hollow nanospheres show a larger specific surface area (165.5 m(2) g(-1)) owing to the hierarchically porous structure (micropores, mesopores, and macropores), resulting in a high photocatalytic performance for the decomposition of methyl orange and phenol aqueous solutions. The present work can provide some new insight into the smart design and preparation of other new metastable hollow materials, and the prepared metastable β-Ag2WO4 hollow nanospheres have various potential applications in chemical reactors, drug-delivery carriers, solar cells, catalysis, and separation and purification fields.
Platinum
telluride (PtTe2) has garnered significant
research enthusiasm owing to its unique characteristics. However,
large-scale synthesis of PtTe2 toward potential photoelectric
and photovoltaic application has not been explored yet. Herein, we
report direct tellurization of Pt nanofilms to synthesize large-area
PtTe2 films and the influence of growth conditions on the
morphology of PtTe2. Electrical analysis reveals that the
as-grown PtTe2 films exhibit typical semimetallic behavior,
which is in agreement with the results of first-principles density
functional theory (DFT) simulation. Moreover, the combination of multilayered
PtTe2 and Si results in the formation of a PtTe2/Si heterojunction, exhibiting an obvious rectifying effect. Moreover,
the PtTe2-based photodetector displays a broadband photoresponse
to incident radiation in the range of 200–1650 nm, with the
maximum photoresponse at a wavelength of ∼980 nm. The R and D* of the PtTe2-based
photodetector are found to be 0.406 A W–1 and 3.62
× 1012 Jones, respectively. In addition, the external
quantum efficiency is as high as 32.1%. On the other hand, the response
time of τrise and τfall is estimated
to be 7.51 and 36.7 μs, respectively. Finally, an image sensor
composed of a 8 × 8 PtTe2-based photodetector array
was fabricated, which can record five near-infrared (NIR) images under
980 nm with a satisfying resolution. The result demonstrates that
the as-prepared PtTe2 material will be useful for application
in NIR optoelectronics.
Palladium diselenide (PdSe 2 ), a noble transition metal dichalcogenide has attracted increasing attention in recent years due to its outstanding semiconductor properties. In this study, 2D PdSe 2 nanofilms with thicknesses ranging from 2 to 28 nm and their heterostructures with Si substrates (PdSe 2 /Si heterostructures) were synthesized via a simple selenization method. Electrical transport characterizations based on field-effect transistor devices indicate that the few-layer PdSe 2 nanofilms exhibit a p-type semiconducting behavior. The optimal sensing performance of the PdSe 2 /Si-8 sensor (8 nm-thick PdSe 2 ) exhibits a comparable response toward NO 2 gas (ΔR/R a = ∼7.2% to 100 ppb and ∼18% to 1 ppm) at room temperature (RT). This response may result from the heterostructure effect and maze-type surface. Additionally, the PdSe 2 /Si-8 sensor has selectivity toward NO 2 compared with other gases including NO, H 2 , CO, NH 3 , and C 2 H 5 OH. Furthermore, density functional theory (DFT) calculations reveal the largest adsorption energy and charge transfer between NO 2 and the PdSe 2 surface, which coincides well with the experimental results. Moreover, the PdSe 2 /Si-8 sensor also exhibits repeatability and long-term stability during about 4 months at RT. These results indicate that the PdSe 2 /Si heterostructures may be a promising nanomaterial for room-temperature NO 2 gassensing devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.