Diluted Magnetic Semiconductor Nanowires Prepared by the Solution-Liquid-Solid Method

Fast near-infrared photodetectors from p-type SnSe nanoribbons

Low-dimensional tin selenide nanoribbons (SnSe NRs) show a wide range of applications in optoelectronics fields such as optical switches, photodetectors, and photovoltaic devices due to the suitable band gap, strong light-matter interaction, and high carrier mobility. However, it is still challenging to grow high-quality SnSe NRs for high-performance photodetectors so far. In this work, we successfully synthesized high-quality p-type SnSe NRs by chemical vapor deposition and then fabricated near-infrared photodetectors. The SnSe NR photodetectors show a high responsivity of 376.71 A W^-1, external quantum efficiency of 5.65 × 10⁴%, and detectivity of 8.66 × 10¹¹Jones. In addition, the devices show a fast response time with rise and fall time of up to 43μs and 57μs, respectively. Furthermore, the spatially resolved scanning photocurrent mapping shows very strong photocurrent at the metal-semiconductor contact regions, as well as fast generation-recombination photocurrent signals. This work demonstrated that p-type SnSe NRs are promising material candidates for broad-spectrum and fast-response optoelectronic devices.

Solution-Liquid-Solid Growth and Catalytic Applications of Silica Nanorod Arrays

As an analogue to the vapor-liquid-solid process, the solution-liquid-solid (SLS) method offers a mild solution-phase route to colloidal 1D nanostructures with controlled sizes, compositions, and properties. However, direct growth of 1D nanostructure arrays through SLS processes remains in its infancy. Herein, this study shows that SLS processes are also suitable for the growth of nanorod arrays on the substrate. As a proof of concept, seedless growth of silica nanorod arrays on a variety of hydrophilic substrates such as pristine and oxide-modified glass, metal sheets, Si wafers, and biaxially oriented polypropylene film are demonstrated. Also, the silica nanorod arrays can be used as a new platform for the fabrication of catalysts for photothermal CO2 hydrogenation and the reduction of 4-nitrophenol reactions. This work offers some fundamental insight into the SLS growth process and opens a new avenue for the mild preparation of functional 1D nanostructure arrays for various applications.

Effect of Mn2+ substitution on the structure, properties and HER activity of cadmium phosphochlorides

Cadmium phosphochlorides, Cd4P2Cl3 and Cd7P4Cl6, possess cadmium atoms differently bonded to chlorine and phosphorus ligands. A combined experimental and theoretical study has been carried out to examine the effect of manganese substitution in place of cadmium in these compounds. Experimentally it is found that manganese prefers the Cd7P4Cl6 phase over Cd4P2Cl3. First-principles calculations reveal, stabilization of Cd7P4Cl6 upon Mn-substitution with a significant reduction in the formation energy when Mn2+ is substituted at Cd-sites coordinated octahedrally by Cl-ligands. Substitution of Mn2+ at two different Cd-sites in these compounds not only alters their formation energy differently but also causes a notable change in the electronic structures. In contrast to n-type conductivity in pristine Cd7P4Cl6, Mn2+ substituted Cd7-y Mn y P4Cl6 analogues exhibit p-type conductivity with a remarkable enhancement in the photochemical HER activity and stability of the system. Photochemical properties of pristine and substituted compounds are explained by studying the nature of charge carriers and their dynamics.

Anomalous optical and magnetic behavior of multi-phase Mn doped Zn(2)SiO(4) nanowires: a new class of dilute magnetic semiconductors

We present the synthesis of Mn doped Zn(2)SiO(4) dense nanowire bundles using the VLS mode of growth with unusual optical and magnetic properties. The synthesized Zn(2)SiO(4) nanowires were identified with two phases, α-Zn(2)SiO(4) as the major phase and β-Zn(2)SiO(4) as the minor phase. XPS studies confirmed that Zn(2)SiO(4) nanowires were Zn rich and Mn doped. Temperature dependent photoluminescence (PL) measurements showed three distinct emission bands: green, yellow and red due to Mn doping in the α-phase, β-phase and the substitution of Si with Mn in the α-phase, respectively. The PL analysis showed that these emission bands followed anomalous Berthelot-type behavior. The carrier escape energies were 70 ± 3 meV, 49 ± 2 meV and 65 ± 4 meV for the 530, 570 and 660 nm bands, respectively, while the radiation rates (Er =) were 1.0 ± 0.4 meV, 3.10 ± 1.10 meV and 1.4 ± 0.4 meV corresponding to the three respective bands. Mn doping of Zn(2)SiO(4) nanowires induced ferromagnetism, which was observed above room temperature, with a Curie temperature well above 380 K. The observation of magnetic behavior in this class of semiconductors has potential applications in high temperature spintronics and magneto-optical devices.

Facile synthesis of highly efficient one-dimensional plasmonic photocatalysts through Ag@Cu₂O core-shell heteronanowires

A novel class of one-dimensional (1D) plasmonic Ag@Cu2O core-shell heteronanowires have been synthesized at room temperature for photocatalysis application. The morphology, size, crystal structure and composition of the products were investigated by XRD, SEM, TEM, XPS, and UV-vis instruments. It was found the reaction time and the amount of Ag nanowires play crucial roles in the formation of well-defined 1D Ag@Cu2O core-shell heteronanowires. The resultant 1D Ag@Cu2O NWs exhibit much higher photocatalytic activity toward degradation of organic contaminants than Ag@Cu2O core-shell nanoparticles or pure Cu2O nanospheres under solar light irradiation. The drastic enhancement in photocatalytic activity could be attributed to the surface plasmon resonance and the electron sink effect of the Ag NW cores, and the unique 1D core-shell nanostructure.

W18O49 nanowire alignments with a BiOCl shell as an efficient photocatalyst

Top-down nanostructure engineering and band engineering are promising methods for fabricating efficient photocatalysts with enhanced optical and electronic properties; however, composites with simultaneously engineered structure and band are very rare. Herein, we constructed a unique architecture composed of a W18O49 nanowire alignment core and porous BiOCl shell (WA@BiOCl), which combined the advantages of both an assembly structure and a type II core-shell heterojunction. The W18O49 alignments (WA) were synthesized using a "one-pot" solvothermal treatment of WCl6/NaNO3via NO3(-)-mediated assembly, whereas the W18O49 nanowires with BiOCl shell (W@BiOCl) were obtained using WCl6/BiCl3. Then, WA@BiOCl, in contrast to W@BiOCl alignments, were fabricated when WCl6 and Bi(NO3)3 were present in the starting mixture. Optical absorption, photoelectrochemical measurements and photoluminescence characterizations show that either the alignments or the core-shell heterojunctions can enhance light harvesting, photo-charge transfer and collection. As a synergetic result, the WA@BiOCl architecture exhibited very high photoactivity and photostability. Under UV-vis (or vis) irradiation, WA@BiOCl is 2.43 (1.93), 3.93 (2.73) and 5.34 (3.44)-fold more active than W@BiOCl, WA and W18O49, respectively. The results demonstrate that the simultaneous nanostructure and band engineering can produce a more efficient photocatalyst than a single strategy alone, which suggests a potential method for the fabrication of photocatalysts in the fields of environment and energy.

Ultra-small fluorescent inorganic nanoparticles for bioimaging

The recent advances of ultra-small fluorescence inorganic nanoparticles including quantum dots, metal nanoclusters, carbon and graphene dots, up-conversion nanocrystals, and silicon nanoparticles have been comprehensively reviewed.

One-dimensional CdS nanostructures: a promising candidate for optoelectronics

As a promising candidate for optoelectronics, one-dimensional CdS nanostructures have drawn great scientific and technical interest due to their interesting fundamental properties and possibilities of utilization in novel promising optoelectronical devices with augmented performance and functionalities. This progress report highlights a selection of important topics pertinent to optoelectronical applications of one-dimensional CdS nanostructures over the last five years. This article begins with the description of rational design and controlled synthesis of CdS nanostructure arrays, alloyed nanostructucures and kinked nanowire superstructures, and then focuses on the optoelectronical properties, and applications including cathodoluminescence, lasers, light-emitting diodes, waveguides, field emitters, logic circuits, memory devices, photodetectors, gas sensors, photovoltaics and photoelectrochemistry. Finally, the general challenges and the potential future directions of this exciting area of research are highlighted.

Field-effect transistors fabricated from diluted magnetic semiconductor colloidal nanowires

Field-effect transistors (FETs) fabricated from undoped and Co(2+)-doped CdSe colloidal nanowires show typical n-channel transistor behaviour with gate effect. Exposed to microscope light, a 10 times current enhancement is observed in the doped nanowire-based devices due to the significant modification of the electronic structure of CdSe nanowires induced by Co(2+)-doping, which is revealed by theoretical calculations from spin-polarized plane-wave density functional theory.

Electrochemically controlled auger quenching of Mn²+ photoluminescence in doped semiconductor nanocrystals

Auger processes in colloidal semiconductor nanocrystals have been scrutinized extensively in recent years. Whether involving electron-exciton, hole-exciton, or exciton-exciton interactions, such Auger processes are generally fast and hence have been considered prominent candidates for interpreting fast processes relevant to photoluminescence blinking and multiexciton decay. With recent advances in the chemistries of nanocrystal doping, increasing attention is now being paid to analogous photophysical properties of colloidal-doped semiconductor nanocrystals. Here, we report the first investigation of the effects of electron-dopant exchange interactions on dopant luminescence in doped semiconductor nanocrystals. Using electrochemical techniques, electrical control of charge-carrier densities in films of colloidal Mn(2+)-doped CdS quantum dots has been achieved and used to demonstrate remarkably effective Auger de-excitation of photoexcited Mn(2+). The doped nanocrystals are found to be substantially more sensitive to Auger de-excitation than their undoped analogues, a result shown to arise primarily from the long Mn(2+) excited-state lifetime. This observation of exceptionally effective Auger quenching has broader implications in areas of high-power, single-particle, or electrically driven luminescence of doped semiconductor nanocrystals, and also suggests interesting opportunities for modulating Mn(2+) photoluminescence intensities on sublifetime time scales, or for imaging charge carriers in nanocrystal-based devices.