Huimin Wang,Tingting Wang,Zibin Huang,Yizhuo Liu,Dehui Leng,Junli Wang
The growth of metal chalcogenide nanowires (NWs) on metal substrates is challenging work since the direct reactions taking place between the chalcogen (S, Se or Te) and zero-valent metal (M0) are frequently unable to regulate the crystallization of nanocrystals in an anisotropic one-dimensional (1D) manner. We here report the use of Ag2Se seeds as catalyst particles to realize the growth of metal selenide (MSe) NWs on their respective metal foil or flakes, including ZnSe/Zn, CdSe/Cd, and MnSe/Mn material systems. Metal foil or flakes (M = Zn, Cd and Mn) serve as a support substrate as well as a metal cation source during the NW synthesis. The preformed Ag2Se seeds play the roles of not only catalytic particles that initiate a so-called solution–solid–solid process to produce crystalline MSe NWs on metal substrates, but also inert impurities that promote an electrochemical anodic reaction of the metal to supply metal cations (M0 − 2e → M2+) for the NW formation. The microstructural studies by HRTEM reveal the polytypism and particularly the diameter-dependence of crystal phases and growth directions in the resulting MSe NWs, which can be rationalized from the viewpoints of the energetics and the catalyst/NW interfacial structures. These semiconductor NWs grown on metal foil or flakes may find wide use in photoelectric catalysis and devices without a transfer process of free-standing NWs onto a conductive support substrate.
Broadband optoelectronic devices intrigue enormous interests on account of their promising potential in optical communications, sensors and environmental monitoring. PbSe nanocrystals are promising candidates for the construction of next-generation photodetectors due to their fascinating intrinsic properties and solution-processed compatibility with varied substrates. Here, we report the fabrication of a broadband photodetector on the basis of high-quality solution-processed PbSe nanorods in rock-salt phase grown along unconventionally anisotropic growth direction of <112> zone axis. The rock-salt PbSe nanorods are synthesized in solution phase over the catalysis of Ag 2 Se with relatively high-temperature body-centered cubic phase via a solution-solid-solid growth regime using oleylamine and oleic acid as solvents and stabilizer surfactants, from which the PbSe nanorods with the unconventionally anisotropic growth direction are controllably grown in size and shape in the synthetic procedure typically with about 17 nm in diameter and 58 nm in length on average. Meanwhile, the PbSe nanorods-based photodetector exhibits a broadband response from 405 to 1,064 nm with a high responsivity of 0.78 A·W −1 and a fast response time of 17.5 µs. The response time is much faster in comparison with most of the PbSe-based photodetectors with response time in millisecond level.
In this work, we combine the catalytic growth and ligand control mechanisms to synthesize ultrathin/ultralong ZnSe nanowires (NWs). Ag 2 Se catalyst seeds initiate the NW growth and significantly cause the increase of the NW lengths up to several micrometers. The long-chain amine mixture of oleylamine and 1-dodecylamine acts as reaction medium and ligands (or surfactants) to control the sizes of Ag 2 Se seeds and ZnSe NWs within several nanometers (the mean diameter of NWs: ∼5.5 nm). The microstructure studies by HRTEM reveal the presence of zinc blende (ZB)/wurtzite (W) alternations and a number of stacking faults and twins within individual ZnSe ultrathin NWs. These NWs exhibit optical quantum confinement effect due to the diameters smaller than the theoretical exciton Bohr diameter of bulk ZnSe. Raman spectrum and photoelectronic performance under white light illumination are also presented.
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