Se Nanorods Research Articles

Insights into enhanced visible light photocatalytic activity of t-Se nanorods/BiOCl ultrathin nanosheets 1D/2D heterojunctions

A novel multidimensional heterojunction, the 1D trigonal Se nanorods (t-Se NRs) dissociated from CdSe QDs germinating on the 2D BiOCl ultrathin nanosheets, was successfully synthesized via a facile hybridization method. Such unique nanocomposite served as an efficient visible-light-driven photocatalyst for the photodegradation of the tetracycline hydrochloride (TC-HCl) solution. The obviously enhanced photocatalytic performance compared with pure BiOCl was mainly attributed to the introduction of Se NRs, which greatly enhanced the optical absorption in visible-light region and suppressed the recombination rate of electron-hole pairs by steering the charges migrating in a special manner. Specially, t-Se NRs in BiOCl system played an integral and important role as holes transfer channels, impelling more photogenerated electrons of BiOCl to participate in the photocatalytic process. Reactive species trapping experiments indicated the main reactive species were O2– radicals, which were generated by the collisions of excited electrons and molecular oxygen. Meanwhile, the radically increased ESR peak of O2– radicals for the heterogenous materials demonstrated successful release of abundant high-energy electrons. This work could be extended to the design of other robust 1D/2D heterojunction photocatalysts in application to the environmental demands.

Hydrothermal transformation of SnSe crystal to Se nanorods in oxalic acid solution and the outstanding thermoelectric power factor of Se/SnSe composite

The present work demonstrates the synthesis of one-dimensional (1D) Se nanorods with ~50 nm diameter by hydrothermal transformation of SnSe crystals in oxalic acid solution and suggests the reaction mechanism for this chemical transformation. SnSe particles react with oxalic acid to generate numerous Se nuclei, which crystallize into Se nanorods due to the intrinsic character of the 1D growth of Se. The resulting Se/SnSe composite exhibits outstanding thermoelectric power factor without the aid of any rare dopants, which is higher than both undoped polycrystalline SnSe and SnSe doped with Pb and Cu.

Functionalized self-assembly of colloidal CdX (X = S, Se) nanorods on solid substrates for device applications.

In comparison to randomly oriented nanorods (NRs), self-assembly of the colloidal CdX (X = S, Se) NRs into well-organized large-scale structures results in unique collective properties. Moreover, the anisotropic structural features of self-assemblies preserved from colloidal CdX (X = S, Se) NRs have opened up exciting opportunities in the field of nanotechnology applications. We present the latest strategies for the self-assembly of colloidal NRs on solid substrates, and further focus on the self-assembled NRs for applications in devices. Advanced progress in the preparation of NR building blocks on the basis of nanofabrication techniques and comprehensive studies on the interactions of NRs with substrates will remarkably expand the application of colloidal semiconductor NRs. Understanding and mastering the driving forces behind the assembly of the NRs is the key goal of engineering future functional structures based on NRs.

Symmetry-Breaking Segmented Selenium Nanorods and Nanowires: Synthesis via Coupling of Nanorods

We present a facile route to prepare selenium nanorods (SeNRs) with alternating symmetry-breaking segments dispersed in aqueous solution. The key roles in this preparation include an assistance provided by the carboxymethyl–cellulose (CMC) and a careful control in particle’s nucleation and growth. Thus, prepared symmetry-breaking segmented SeNRs, namely, SBS-SeNRs, show discrete trigonal and quasi-trigonal phases in the form of repeating quasi-trigonal–trigonal–quasi-trigonal, (tq–t–tq)n, where tq stands for the quasi-trigonal phase in the space group of P321 and t is the trigonal phase in the space group of P3121. Evidence from the particle dimensions analysis during the growth and the result of post-synthesis surface modification showed that the SBS-SeNRs grow via two different particle couplings. The first one was found in the early stage that very short monoclinic Se nanorods couple together with a simultaneous phase transition to trigonal SeNR. The second coupling occurs at the later stage by the coupling of the (tq–t–tq)-SeNRs, which are formed via a growth of symmetry-breaking Se at both ends of the t-SeNR. Meanwhile, we designed an experiment by conducting the silica coating via sol–gel process to further prove the symmetry-breaking segmented nanostructure. The coating proceeded preferentially on the trigonal segments of SBS-SeNRs rather than the quasi-trigonal segments to form a float-like core−shell nanostructure, as well as a string of beads-like one in the case of selenium nanowires (SeNWs). The synthesis of SBS-SeNRs demonstrates the segmented nanomaterials are no longer limited in the combination of different compositions, but opens up a possibility for the versatile intriguing segmented nanomaterials in the future.

One-pot synthesis of cubic ZnSe entangled nanowires and hexagonal Se nanorods

Se nanorods, ZnSe nanowires and their mixture can be prepared by a single process at different reaction temperatures between 300 to 360 °C. The Se nanorods are generally longer than 1 μm, while the ZnSe nanowires have an entangled structure and have a diameter and length of 15–20 nm and 0.3–2 μm, respectively.

Hydrothermal synthesis, characterization, and magnetic properties of cubic MnSe2/Se nanocomposites material

The cubic MnSe2/Se nanocomposites were produced under hydrothermal condition, by reduction of SeCl4 to Se and Se2−, and reaction of the reduced selenium with Mn2+ ion during the next step, in the presence of different surfactants using hydrazine as reductant. The main factors affecting the morphology, the particle size and the phase of the products, such as surfactant, reductant and its amount, reaction temperature and time were studied. The pure Se or a mixture of Se and MnSe2 nanorods were obtained in the presence of different surfactants and small amounts of hydrazine. The cubic MnSe2/Se nanocomposites were formed at 120°C for 12h or longer periods of time, in the presence of polyethylene glycol (PEG) and large amounts of hydrazine. The size of the as-prepared cubes decreases with increasing the reaction time. With increasing temperature of reaction from 120°C to 180°C, the morphology of the products changes from cubes to the mixture of nanorods and nanoparticles.

Dielectrophoretic trapping of selenium nanorods for use in device applications

Dielectrophoretic alignment of the Selenium (Se) nanorods is reported for electrical characterization and possible applications as micro/nano devices. Selenium nanorods were successfully synthesized using a reverse microemulsion process. The produced material was investigated structurally using X-ray diffraction and transmission electron microscope. Suspensions of the Se powder in the concentration of 0.1 (g/l) were prepared in pure ethanol. Interdigitated platinum electrodes were employed for manipulation of suspended materials in the fluid. When Se particles were exposed to the platinum electrodes in two frequencies of 10 and 100 kHz, dielectrophoretic force captured suspended particles onto the interdigitated micro-electrode array. The trapped Se nanorods were aligned along the electric field lines and bridged the electrode gaps. Dielectrophoretic entrapment of Se nanorods on microelectrode was also detected by impedance measurements. The device was characterized and can potentially be used as a nanodevice.

Near‐Infrared‐Emitting CdxHg1−xSe Nanorods Fabricated by Ion Exchange in an Aqueous Medium

Whereas CdSe nanorods that are grown in organic solution have a hexagonal wurtzite structure, which is the limiting case for exchange, HgSe is more commonly encountered as a cubic zinc blende system. An exchange process was performed at room temperature and at atmospheric pressure in an aqueous environment after phase transfer of the original CdSe nanorods, which reinforced the tendency for the endpoint of HgSe to be cubic. Consequently, we observed that under ambient conditions, the exchange process terminated with an average composition of only Cd(0.9)Hg(0.1)Se. Following the changes during the process by optical spectroscopy and high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM), we observed that the Hg(2+) ions diffused into the rods to a point limited by the formation of stacking faults due to the different lattice structures of the two limiting cases of zinc blende and wurtzite. HAADF-STEM and energy dispersive spectroscopy analyses also confirmed that the Hg substitution did not occur uniformly throughout the individual nanorods, as Hg-poor and Hg-rich regions coexist around the stacking faults. The formation of near-infrared-emitting alloyed Cd(x)Hg(1-x)Se nanorods in an aqueous medium highlights the subtle dependence of the ion-exchange process on the differences in the crystal structures of the two endpoint lattices.

Effect of nickel salt precursors on morphology, size, optical property and type of products (NiSe or Se) in hydrothermal method

NiSe micro/nanocrystals with multiform morphologies, including particles, rods and flowers were prepared by hydrothermal method from different Ni salts: NiBr2, Ni(ClO4)2⋅6H2O, NiCl2⋅6H2O and NiSO4⋅6H2O. Se nanorods were produced simply by varying the nickel salts to Ni(CH3COO)2⋅H2O and Ni(NO3)2⋅6H2O. The process was performed at 180°C for 12h and cetyltrimethyl ammonium bromide (CTAB) and hydrazine hydrate (N2H4⋅H2O) used as surfactant and reductant, respectively. The samples were analyzed by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electronic diffraction (SAED) and X-ray energy dispersive spectroscopy (EDS). The synthesis was performed conveniently and safely.

Biosynthesis and structural characteristics of selenium nanoparticles by Pseudomonas alcaliphila

In this paper, we report that selenium (Se) nanoparticles were first biosynthesized by Pseudomonas alcaliphila with a simple and eco-friendly biological method. The structural characteristics of Se nanoparticles were examined. The results showed that spherical particles appeared with diameters ranging from 50 to 500 nm during incubation and Se nanorods were present after incubating in an aqueous reaction solution for 24h. However, the formation of Se nanorods was interrupted when 5% (w/v) poly(vinyl pyrrolidone) (PVP) was added in the aqueous reaction solution, obtaining stable spherical Se nanoparticles with a diameter of about 200 nm.

Expanding the One-Dimensional CdS–CdSe Composition Landscape: Axially Anisotropic CdS1–xSex Nanorods

We report the synthesis and characterization of CdS(1-x)Se(x) nanorods with axial anisotropy. These nanorods were synthesized via single injection of a mixture of trioctylphosphine sulfur and selenium precursors to a cadmium-phosphonate complex at high temperature. Transmission electron microscopy shows nanoparticle morphology changes with relative sulfur and selenium loading. When the synthetic selenium loading is between 5% and 10% of total chalcogenides, the nanorods exhibit pronounced axial anisotropy characterized by a thick "head" and a thin "tail". The nanorods' band gap red shifts with increasing selenium loading. X-ray diffraction reveals that CdS(1-x)Se(x) nanorods have a wurtzite crystal structure with a certain degree of alloying. High-resolution and energy-filtered transmission electron microscopy and energy-dispersive X-ray spectroscopy confirm the head of the anisotropic nanorods is rich in selenium, whereas the tail is rich in sulfur. Time evolution and mechanistic studies confirm the nanorods form by quick growth of the CdSe-rich head, followed by slow growth of the CdS-rich tail. Metal photodeposition reactions with 575 nm irradiation, which is mostly absorbed by the CdSe-rich segment, show effective electronic communication between the nanorod head and tail segments.

Facile, one-step controlled synthesis of Se nanocrystals in the presence of l-tyrosine

Abstract Se with different morphologies was synthesized using l -tyrosine as reducing agent and soft template by means of hydrothermal method. The method was simple and convenient to handle. The reaction process was monitored using ultraviolet–visible spectroscopy (UV–vis) and Fourier-transform infrared spectroscopy (FTIR). The morphology and crystalline phase were determined by transmission electron microscopy (TEM), scanning electronic microscopy (SEM) and X-ray diffraction (XRD) pattern. The results show that the morphologies and the crystalline phases of Se can be easily controlled. By varying the concentration ratio of l -tyrosine to selenious acid, the morphologies and crystalline phases of Se were not changed, but the diameter of Se was different. Se nano-rods are obtained in the lower temperature, and there is a transformation of microspheres into nanorods of Se with the increase of reaction time or reaction temperature. In addition, we discuss the possible mechanism of the reduction of SeO 3 2− ions by l -tyrosine. The eco-friendly, biogenic synthesis strategy could be widely used for preparing inorganic/organic biocomposites.

Bovine Serum Albumin Driven Interfacial Growth of Selenium–Gold/Silver Hybrid Nanomaterials

Selenium (Se) nanorods (NRs) capped with BSA were used as precursor to synthesize Se-Au/Ag hybrid nanocrystals (NCs). Aqueous Au/Ag ions in the presence of fixed amount of purified dried Se NRs were reduced by ascorbic acid at 80 degrees C to generate respective nucleating centres which subsequently grew on the capped BSA hot spots. The hybrid NCs thus obtained were characterized by SEM, TEM, and EDS analysis while their synthesis was monitored simultaneously by UV-visible absorbance due to the surface plasmon resonance of Au and Ag nanoparticles (NPs). In both cases, a gradual decrease in the absorbance of Au/Ag NPs with respect to reaction time was observed which indicated a diminishing number density of such particles in colloidal aqueous phase. SEM and TEM analyses then explained the presence of Au NPs in self assembled ball shaped aggregates and their selective adsorption on Se NRs, whereas no self aggregated balls of Ag NPs were observed and they always grew on the Se NRs. The results were discussed on the basis of different routes followed by the Au and Ag nucleating centres to produced hybrid nanomaterials.

Room-temperature synthesis of single-crystalline Se nanorods with remarkable photocatalytic properties

We demonstrated for the first time that single-crystalline Se nanorods (NRs), prepared with a facile chemical reduction approach at room temperature, may display noticeable catalytic activities toward methylene blue degradation in dark environment after subjected to a short period of irradiation. Such capability of photocatalysis in the dark for Se NRs was attributed to the memory effect related to pre-irradiation treatment. The result of spin-trapping electron paramagnetic resonance measurement suggests that a sustained supply of OH radicals could be attained for Se NRs upon the cease of irradiation, which is accountable for the memory photocatalytic effect as revealed in the dark. As compared to the commercial P-25 TiO2 powder and Se nanoparticles, the as-synthesized Se NRs exhibited superior photocatalytic performance under UV illumination, demonstrating their potential as active photocatalysts in relevant redox reactions. Furthermore, the recycling test reveals that Se NRs could be promisingly utilized in the long-term course of photocatalysis. The present Se NRs may find potential use for unique photocatalytic applications, in which typical photocatalysis prevails under light illumination, while memory photocatalytic effect takes over when irradiation is interrupted.

Selective Synthesis of Fe7Se8 Polyhedra with Exposed High‐Index Facets and Fe7Se8 Nanorods by a Solvothermal Process in a Binary Solution and Their Collective Intrinsic Properties

Fe(7)Se(8) polyhedra with high-index facets and Fe(7)Se(8) nanorods can be selectively synthesized by a solvothermal reaction in a mixed solvent of diethylenetriamine (DETA) and deionized water (DIW). It is found that the morphologies of Fe(7)Se(8) nanocrystals can be effectively controlled by adjusting the volume ratio of DETA and DIW. The unusual polyhedral crystals are bounded by two {001} and twelve {012} facets. The intrinsic properties of Fe(7)Se(8) nanocrystals have been investigated. Magnetic measurements indicate that the obtained polyhedra and nanorods show a weak ferromagnetic ordering at room temperature. In particular, a new photoluminescence emission at 403 nm from the Fe(7)Se(8) nanocrystals has been observed. The described solvothermal reaction in a mixed solvent may be extended to the synthesis of other transition-metal chalcogenide crystals with controlled shape, facets, and structure, which may bring new functionalities.

Synthesis and Characterization of Cu(InxB1−x)Se2 Nanocrystals for Low-Cost Thin Film Photovoltaics

Chalcopyrite quaternary semiconductor Cu(In(x)B(1-x))Se(2) nanocrystals have been successfully prepared via a relatively simple and convenient solvothermal route. The effect of different solvents on the formation of the product also indicates that diethylenetriamine is the optimal solvent for this reaction. The device parameters for a single junction Cu(In(x)B(1-x))Se(2) solar cell under AM1.5G are as follows: an open circuit voltage of 265 mV, a short-circuit current of 25.90 mA/cm(2), a fill factor of 34%, and a power conversion efficiency of 2.34%. Based on a series of comparative experiments under different reaction conditions, the probable formation mechanism of crystal Cu(In(x)B(1-x))Se(2) nanorods is proposed.

Highly efficient orange emission in ZnO:Se nanorods

The origin of the visible emissions in ZnO nanostructures is a long-standing issue. In this work, a strong orange emission around 2.1 eV in ZnO:Se nanorods is reported. Temperature-dependent photoluminescence (PL) and PL decay results indicate that radiative recombination dominates the overall decay process, leading to highly efficient orange emission at room temperature. It is proposed that Se acts as isoelectronic centers and no evidence of ZnO1−xSex alloy formation is found. Based on the PL excitation results, we propose a Se-induced impurity band model to describe the photophysics of the orange emission.

Synthesis of Sb<SUB>2</SUB>E<SUB>3</SUB> (E = S, Se) Nanorods with a Flat Cross Section by a Rapid Hot Injection Method

We report herein a simple colloidal synthesis route, i.e., rapid injection of E (E = S, Se) source into a hot solvent (1-octadecence, ODE) containing antimony precursor (antimony stearate), to grow Sb2E3 nanorods. The as-prepared nanorods were extensively characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM). The mechanism for growth of Sb2E3 nanorods was also clarified from the view of crystal structure-directed growth. We believe that the method present here is a more straightforward and cost-effective route to prepare Sb2E3 nanocrystals with high quality.

Surface Activity of Highly Hydrophobic Surfactants and Platelike PbSe and CuSe Nanoparticles

Lead selenide (PbSe) and copper selenide (CuSe) nanoparticles were synthesized in aqueous phase at a relatively mild temperature (85 °C) in the presence of various cationic Gemini surfactants (12−2−12, 12−0−12, and 16−2−16) as capping/stabilizing agents. All nanoparticles exhibited clear core−shell (surfactant) morphologies. PbSe reactions produced predominantly platelike cubic morphologies along with long Se nanorods (NRs) as a reaction byproduct. CuSe particles were polyhedral thin plates with perforations. High resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD) measurements were used to characterize the shape and structure of the particles. HRTEM allowed us to measure the precise thickness of the surfactant shell around each nanocrystal (NC) which was in excellent agreement with the length of the surfactant hydrocarbon tail. Infrared spectroscopic (FT-IR) studies suggested a strong affinity of cationic surfactant for NC ...

Aerobic microbial manufacture of nanoscale selenium: exploiting nature’s bio-nanomineralization potential

The potential of the environment to yield organisms that can produce functional bionanominerals is demonstrated by selenium-tolerant, aerobic bacteria isolated from a seleniferous rhizosphere soil. An isolate, NS3, was identified as a Bacillus species (EU573774.1) based on morphological and 16S rRNA characterization. This strain reduced Se(IV) under aerobic conditions to produce amorphous alpha Se(0) nanospheres. A room-temperature washing treatment was then employed to remove the biomass and resulted in the production of clusters of hexagonal Se(0) nano-rods. The Se(0) nanominerals were analyzed using electron microscopy and X-ray diffraction techniques. This Bacillus isolate has the potential to be used both in the neutralizing of toxic Se(IV) anions in the environment and in the environmentally friendly manufacture of nanomaterials.