Characterisation of one-dimensional CdS nanorods synthesised by solvothermal method

One-dimensional (1D) cadmium sulfide nanorods were successfully synthesised using cadmium nitrate and sulfur powder as starting materials and polyvinyl alcohol (PVA, MW = 1 25,000) as a capping agent in ethylenediamine as a solvent by solvothermal method at 200°C for 24 and 72 h. X-ray diffraction patterns (XRD) indicated a single phase of hexagonal wurtzite CdS structure, of which the results are in accordance with those of selected area electron diffraction (SAED). The morphologies of CdS were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which showed 1D nanorods. The length and diameter of CdS nanorods were increased when PVA was added and the reaction times were prolonged. High resolution transmission electron microscopy (HRTEM) showed that growth direction of wurtzite CdS nanorods is along [001] direction or c-axis. Raman spectra presented the 1LO and 2LO at 299.36 and 600.72 cm^?1, respectively. The 2LO/1LO intensity ratios were increased when the length of CdS nanorods became longer.     

One-dimensional cadmium sulfide (CdS) nanostructures by the solvothermal process: Controlling crystal structure and morphology aided by different solvents

Cadmium sulfide (CdS) nanowires and nanorods with different aspect ratios were successfully synthesized by the solvothermal method aided with various solvents, namely ethylenediamine, ethanolamine and triethylene tetraamine. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses revealed that, highly pure CdS nanostructures were crystallized with different structures and preferable growth orientations depending on solvent nature. Field emission electron microscope (FE-SEM) images showed that the aspect ratio of CdS nanostructures depends upon the dielectric constant and boiling temperature of solvents. CdS nanostructures with the highest aspect ratio in the form of nanowire were obtained using ethylenediamine, whereas CdS nanorods were produced in the presence of ethanolamine and triethylene tetraamine solvents. The absorption edge of CdS nanowires and nanorods showed a blue shift compared with that of bulk CdS due to an increase in their band gap energies.     

CdS:Mn nanorods: solvothermal synthesis and properties

Manganese (0.05-9 mol.%) doped CdS nanorods were synthesized via solvothermal route using ethylenediamine (En) and a mixture of En and water as the solvents. The diameters and the lengths of the doped CdS nanorods varied from 40-100 nm and 600-2500 nm, respectively, with change in the composition of the solvents. The broad photoluminescence (PL) emission from the undoped CdS nanorods centered at approximately 535 nm is found to be blue shifted to 516 nm with the incorporation of Mn in the CdS crystal structure. Also increase in the intensity of the PL was noticed in the Mn doped CdS nanorods for both the solvent systems. Maximum PL intensity was observed for 1 mol.% Mn in case of En system and for 0.5 mol.% Mn in case of En/water system, above which quenching occurred as a result of Mn-Mn clustering. EPR study revealed six-line hyperfine splitting for low Mn concentration in both solvent systems. Increase in the Mn concentration caused EPR signal broadening due to Mn-Mn clustering.     

Synthesis of highly-active single-crystalline TiO2 nanorods and its application in environmental photocatalysis

Highly-active anatase TiO₂ nanorods have been successfully synthesized via a simple two-step method, hydrothermal treatment of anatase/rutile titanium dioxide nanoparticle powder in a composite-hydroxide eutectic system of 1:1 M KOH/NaOH, followed by acid post-treatment. The morphology and crystalline structure of the obtained nanorods were characterized using XRD, TEM, SEM/EDX and BET surface area analyzer. The obtained TiO₂ nanorods have a good crystallinity and a size distribution (about 4-16 nm); with the dimensions of 200-300 nm length and of 30-50 nm diameter. Compared with its precursor anatase/rutile TiO₂ nanoparticles and the titanate nanotubes, the pure anatase TiO₂ nanorods have a large specific surface area with a mesoporous structure. The photocatalytic performance of the prepared nanorods was tested in the degradation of the commercial Cibacrown Red (FN-R) textile dye, under UV irradiation. Single-crystalline anatase TiO₂ nanorods are more efficient for the dye removal.     

Structural and optical characterization of Ni-doped CdS quantum dots

Ni-doped CdS quantum dots have been prepared by chemical precipitation technique. The X-diffraction results indicated that the particle size of Ni-doped CdS nanoparticles is smaller than that of undoped CdS and no secondary phase was observed. The average grain size of the nanoparticles is found to lie in the range of 2.7–4 nm. The compositional analysis results show that Cd, Ni, and S are present in the samples. HRTEM studies reveal that the average particle size of undoped and Ni-doped CdS quantum dots is 2 and 3 nm, respectively. Raman spectra shows that 1LO, 2LO, and 3LO peaks of the Ni-doped CdS samples are slightly red shifted when compared to that of undoped CdS. The absorption edge of Ni-doped CdS nanoparticles is found to shift towards the higher-wavelength (red shift) side when compared to that of undoped CdS and the band gap is observed to lie in the range of 3.79–3.95 eV. This band gap is higher than that of the bulk CdS and is due to quantum confinement effect present in CdS nanoparticles.     

Characterization of cadmium sulfide nanorods prepared by the solvothermal process

Cadmium sulfide nanorods were successfully prepared from cadmium nitrate tetrahydrate and thiourea in ethylenediamine by 200 °C solvothermal reactions using hydroxyethyl cellulose (HEC) as a capping material. X-ray diffraction (XRD), selected area electron diffraction (SAED), and Raman spectroscopy showed that the products were hexagonal wurtzite CdS with the 1st and 2nd harmonic modes at 303.5 and 593.0 cm^− 1, respectively. The intensity ratios of the 2nd to 1st harmonic modes were increased with their aspect ratios, due to the great strength of exciton-phonon coupling. By using scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM) and fast Fourier transformation (FFT), the products were in the shape of nanoparticles in the HEC-free solution, and became nanorods with higher aspect ratios in the HEC-added solutions — especially with longer reaction time. These nanorods were single crystals with growth in the [001] direction.     

Synthesis and characterizations of CdS nanorods by SILAR method: effect of film thickness

In this investigation, we have successfully synthesized CdS nanorods by simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method. The effect of film thickness on the physico-chemical properties such as structural, morphological, wettability, optical, and electrical properties of CdS nanorods has been investigated. The XRD pattern revealed that CdS films are polycrystalline with hexagonal crystal structure. SEM and TEM images showed that CdS film surface are composed of spherical grains along with some spongy cluster and an increase in film thickness up to 1.23 μm causes the formation of matured nanorods having diameter 150–200 nm. The increases in water contact angle form 105° to 130° have been observed as film thickness increases from 0.13 to 1.23 μm indicating hydrophobic nature. The optical band gap was found to be increased from 2.02 to 2.2 eV with increase in film thickness. The films showed the semiconducting behavior with room temperature electrical resistivity in the range of 10⁴–10⁶ Ω cm and have n-type electrical conductivity.     

Structural,optical and magnetic properties of cobalt-doped CdS dilute magnetic semiconducting nanorods

Nanostructures of dilute magnetic semiconductors (DMS) in which a part of host material is replaced by a magnetic dopant are the promising candidates for spintronic devices. Pure and cobalt-doped DMS nanorods of CdS have been synthesized by solvothermal method. The effect of doping as well as the size of synthesized nanorods on structural, optical, and magnetic properties has been investigated. Transmission electron microscopy confirms the nanorods' morphology with an average diameter between 7 and 11 nm. Structural study reveals the formation of single phase hexagonal wurtzite structure of CdS with P6₃mc space group. UV–visible absorption spectra confirms that the band gap of the synthesized nanorods lie in the visible region between 2.46 and 2.72 eV. Photoluminescence spectra show defects-free nature of synthesized nanorods. The hump of emission band, around 430 nm in Co-doped CdS nanorods, attributes to the direct transition from the energy states created in CdS. Magnetic study reflects the ferromagnetic character of synthesized nanorods with high magnetic saturation, 0.034, 0.041, 0.070 and 0.090 emu g⁻¹ for, respectively, pure, 5%, 10% and 15% Co-doped CdS nanorods. The observed ferromagnetism in the synthesized nanorods have been explained on the basis of F-center (sulfur vacancy) mediated exchange mechanism and indirect interaction among Co (II) centers.     

Room temperature ferromagnetism in solvothermally synthesized pure CdSe and CdSe:Ni nanorods

We report here room temperature ferromagnetism in CdSe and Ni-doped CdSe nanorods. Pure and 3% Ni-doped CdSe nanorods are synthesized by using low temperature solvothermal process by using ethylenediamine as solvent. X-ray diffractogram depicts the wurtzite (hexagonal) structure of the CdSe nanorods. From Transmission Electron Microscopy analysis, it is found that the average diameter of the CdSe nanorods is about 4–5 nm having length of about 50 nm. Magnetic studies are made by the analysis of M–H curves, obtained by using Superconducting Quantum Interference Device. The room temperature ferromagnetic behaviour has been shown by both pure CdSe as well as Ni-doped CdSe nanorods.     

Studies on optical absorption and photoluminescence of thioglycerol-stabilized ZnS nanoparticles

ZnS quantum dots of size 3 nm are prepared at 303 K using ZnSO₄ and Na₂S₂O₃ precursors with thioglycerol as stabilizing agent. Cd²⁺ doped ZnS were prepared by varying doping concentration from 1 to 8 wt.%. ZnS quantum dots were mixed with CdS quantum dots of size 4 nm in the 3:1, 2:1, 1:1, 1:2, 1:3 and 1:4 M ratio. The nanoparticles were characterized by UV–vis, photoluminescence (PL), XRD and high-resolution TEM measurements. The XRD pattern, high-resolution TEM image and SAED pattern reveal that the nanoparticles are in well-crystallized cubic phase. The band gap of ZnS has increased from the bulk value 3.7 to 4.11 eV showing quantum size effect. Excitonic transition is observed at 274 nm in UV absorption and PL emission at 411 nm. Doping with Cd²⁺ red-shifts both UV and PL spectral bands and enhances the PL band of ZnS nanoparticles. Mixing CdS and ZnS quantum dots in different molar ratios shows red-shift of the band edge in the CdS/ZnS hybrid system. In the 1:1 hybrid system of CdS/ZnS nanoparticles, PL band is red-shifted and the intensity is almost doubled with respect to that of CdS nanoparticles.     

Synthesis of ZnO nanorods from aqueous solution

In the present work, crystalline one-dimensional ZnO nanorods were synthesized by a PVP (polyvinylpyrrolidone)-assisted hydrothermal process with zinc acetate as the precursor. The major advantage of this technique is the use of water as the solvent: cheaper and more environmentally friendly than alcohol. The as-synthesized ZnO nanorods have diameters of 50-200 nm and lengths up to 5 μm. X-ray powder diffractometry (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED), Fourier transmission infrared spectroscopy (FTIR) were used to characterize the structural and the chemical features of the ZnO nanorods.     

A simple route to lanthanum hydroxide nanorods

This letter first describes a facile, low-cost, solution-phase approach to the large-scale preparation of lanthanum hydroxide single crystal nanorods at 60 °C without any template and surfactant. X-ray diffraction (XRD) shows that the nanorods are of pure hexagonal structure. The size and morphology of the products were examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Lanthanum hydroxide single crystal nanorods are with diameters of approximately 20 nm and lengths of 150-200 nm. The processes of formation and decomposition for the as-prepared lanthanum hydroxide nanorods were discussed.     

Matrix-assisted pulsed laser deposition of polymer and nanoparticle films

Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique was used to deposit films of Poly(9,9-dioctylfluorene) - PFO and Methoxy Ge Triphenylcorrole [Ge(TPC)OCH3]. The PFO was dissolved in different matrices, like chloroform-CHCl3, tetrahydrofuran - THF and toluene with a 0.5 wt % concentration, while Ge(TPC)OCH3 was diluted in THF with a concentration of 0.01 wt %. The frozen targets were irradiated with a KrF excimer laser. The, films presented good emission properties to be exploited in light emitting devices and gas sensors based on luminescence quenching. The working principle of the MAPLE technique was used for the deposition of colloidal nanoparticles and nanorods, too. TiO2 colloidal nanoparticles (diameter: ∼10 nm) and nanorods (diameter: 5 nm; length: 50 nm) were diluted in deionised water (0.02 wt %) and toluene (0.016 wt %) respectively. The deposited nanostructures preserved dimensions and structural properties of the starting particles and the films showed very interesting electrical responses when exposed to oxidizing gases for sensing applications.     

Synthesis and characterization of cuprous sulfide crystals with novel morphology

Cuprous sulfide (Cu_2−xS) crystals in different stoichiometries were synthesized by hydro- and solvo-thermal methods at 125 °C using Na₂S₂O₃ as sulfur source in pure water, mixed solvents of ethylenediamine (en) and water, and pure en, respectively. The products were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersion spectrometer (EDS), transmission electron microscope (TEM) and selected area electronic diffraction (SAED). Owing to different sulfur sources, crystal structures and morphologies of cuprous sulfides were different from those developed by some former researchers. Novel twelve-fold symmetrical Cu₇S₄ single crystals were synthesized at an en/water volume ratio of 3:1, and they were built up by two layers of about 80-100 nm in thickness. Moreover, the possible growth process had been discussed based on the analyses of detailed configuration of the products.     

Synthesis and morphological control of europium doped cadmium sulphide nanocrystals

Europium doped cadmium sulphide (Cd(0.98)Eu(0.2)S) nanostructures were synthesised by chemical co-precipitation method using ethylene glycol (EG) and deionized water (Eu:CdS-1), and isopropyl alcohol (IPA) and deionized water (Eu:CdS-2) as mixed solvents. It has been found that the nanostructure of the europium doped CdS can be controlled by simply varying the mixed solvent system. Powder XRD pattern reveals the formation of hexagonal (wurtzite) and cubic (zinc blende) structure for Eu:CdS-1, and Eu:CdS-2, respectively. The crystallite size of the sample prepared using IPA and deionized water was measured to be 2.64 nm which is much smaller than that of the sample prepared using EG and deionized water as mixed solvent (3.65 nm). Morphology of the materials can also be changed from flower shaped crystals to paddy like structures by varying the mixed solvents. Band gap values of Eu3+ doped CdS nanocrystals synthesized from two different solvents were estimated using UV-reflectance spectra. The size and crystallinity of the samples were confirmed by HRTEM and SAED analysis. A significant change in the PL emission of the CdS nanocrystals was observed for the europium doped CdS which is mainly due to the presence of EU3+ ions which also play a significant role in the energy transfer process. It was also observed that the shift in the emission and efficiency depends on size and shape of the synthesised nanoparticles.     

Preparation and characterization of KGM/CdS nanocomposite film with low infrared emissivity

In this research, novel organic-inorganic nanocomposite films of Konjac glucomannan (KGM) and CdS were prepared by one-step synthesis. As-prepared films were characterized by IR, TEM and SEM. The results indicated that hexagonal CdS nanoparticles with the sizes of 10 to 100 nm were well dispersed in KGM. The infrared emissivities of the films were characterized by IR-1 infrared emissivity instrument. As results showed, the KGM/CdS nanocomposite films had significantly lower infrared emissivity (8-14 μm), meanwhile when the size of KGM nanoparticles was between 10 and 20 nm and the mole ratio of CdS to KGM was 1.2:1, the film got the lowest infrared emissivity value of 0.011, which would be attributed to the strong synergism effect existing between KGM and CdS nanoparticles.     

Chemical synthesis of CdS nanoparticles and their optical and dielectric studies

Cadmium sulphide nanoparticles were synthesized by chemical displacement reaction method using cadmium nitrate as cadmium source and ammonium sulphide as sulphur source. The CdS samples are characterized using X-ray diffraction, UV–Vis spectroscopy, FTIR spectroscopy, scanning electron microscopy and impedance spectroscopy. CdS nanoparticles are found to possess cubic structure with the crystallite size ~10 nm. The absorption spectra of synthesized CdS nanoparticles revealed the blue shift in excitonic transitions with respect to CdS bulk material, clearly confirming the formation of nanoparticles. The dielectric properties of CdS nanoparticles are studied in the frequency range 10³–10⁷ Hz at room temperature. The dielectric properties of CdS nanoparticles are found to be significantly enhanced specially in the low frequency range due to confinement.     

Quantum confinement effects in Gd-doped CdS nanoparticles prepared by chemical precipitation technique

CdS and Gd-doped CdS nanoparticles have been synthesized by chemical precipitation technique. The X-ray diffraction patterns show that the CdS and Gd-doped CdS nanoparticles exhibit hexagonal structure. The high resolution transmission electron microscope image shows that CdS and Gd-doped CdS nanoparticles have particle size lying in the range of 3.5 to 4.0 nm. Raman spectra show that 1LO, 2LO and 3LO peaks of the Gd-doped CdS nanoparticles are slightly shifted to lower wavenumber side when compared to that of CdS. Optical absorption spectra of Gd-doped CdS nanoparticles shows that absorption edge is slightly shifted towards longer wavelength side (red shift) when compared to that of CdS and this shift is due to the quantum confinement effect present in the samples.     

Solvothermal synthesis and photoluminescence properties of ZnO nanorods and nanorod assemblies from ZnO2 nanoparticles

Without the use of any extra surfactant or template, hexagonal phase ZnO crystallites consisting of individual nanorods or nanorod assemblies were synthesized simply by solvothermal treatment of several nanometer ZnO₂ nanoparticles in three different solvents (including ethanol, 80 wt.% hydrazine hydrate aqueous solution and ethylenediamine) at 150 °C for 24 h. The structures and optical properties of the resultant products were characterized by means of X-ray powder diffraction (XRD), scanning electron microscope (SEM), and room temperature photoluminescence (RTPL) spectra. The RTPL spectra of the resultant products all showed a much stronger ultraviolet bandgap emission peaking at around 387 nm and a weaker emission associated with the defect level. The as-synthesized ZnO crystallites are promising materials for the optoelectronic devices due to their excellent UV emission properties.     

CdS microflowers and interpenetrated nanorods grown on Si substrate: Structural,optical properties and growth mechanism

CdS semiconductor with different morphologies have been achieved by simple thermal evaporation of CdS powder at 1050 °C in a flowing Ar atmosphere. The products were characterized by X-ray diffraction, Scanning electron microscopy, Transmission electron microscopy and Photoluminescence. microflowers and interpenetrative nanorods of CdS were formed on catalyst free Si wafers at a temperature of 700 °C and 600 °C respectively. The flower like structures are composed of many interleaving nanorods which have the uniform diameter of about 700 nm and a well crystalline structure with [0001] as growth direction. The interpenetrative nanorods are found to be bounded with six side facets. X-ray diffraction studies revealed the hexagonal structure in both the products. The formation mechanism of microflowers and interpenetrated nanorods was discussed on the basis of nucleation growth kinetics. Room temperature photoluminescence spectra showed a strong green emission band (at ∼510 nm) from the CdS flower like structures, but on the other hand a red emission shoulder along with strong green emission band was observed for interpenetrative nanorods. These CdS micro/nanostructures with abundant morphologies may find applications in various micro/nanodevices, and the kinetics-driven morphology might be exploited to synthesize similar structures of other functional II–VI semiconductors.