Tin oxide nanocubes, and tin-core/tin oxide-shell nanostructures, with and without a hollow interior

A number of nanoscale tin oxide structures including 2–5 nm tin oxide hollow nanoparticles, 3–5 nm tin oxide nanocubes, 80–120 nm tin-core/tin oxide-shell nanocubes, and hollow tin oxide nanocubes, have been prepared from phenanthroline (phen)-capped Sn nanoparticles. Transmission electron microscopy revealed the existence of a hollow interior in the tin-core/tin oxide-shell nanostructures. It is believed that the low melting Sn core was hollowed out by electron beam irradiation of the sample during microscopy. The 2–5 nm tin oxide hollow nanoparticles and 80–120 nm tin oxide hollow nanocubes had thin but stable shells capable of preserving the integrity of the large cavity within.     

Morphological control of Ni/NiO core/shell nanoparticles and production of hollow NiO nanostructures

Chemical synthesis coupled with a microwave irradiation process allowed for the control of size (6–40 nm), shape, and shell thickness of Ni/NiO core/shell nanoparticles. In this unique synthetic route, the size of Ni nanoparticles (NiNPs) was strongly influenced by the nickel salt-to-stabilizer ratio and the amount of the stabilizer. Interestingly, it was observed that the shape of the nanoparticles was altered by varying the reaction time, where longer reaction times resulted in annealing effects and rupture of the stabilizer micelle leading to distinct shapes of Ni/NiO core/shell nanostructures. Product cooling rate was another important parameter identified in this study that not only affected the shape, but also the crystal structure of the core/shell nanoparticles. In addition, a simple and cost-effective method of microwave irradiation of NiNPs led to the formation of distinctly shaped hollow NiO nanoparticles. These high surface area core/shell nanoparticles with well-controlled morphologies are important and can lead to significant advancement in the design of improved fuel cells, electrochromic display devices, and catalysis systems.     

Ultrasonic irradiation effects on electrochemical synthesis of ZnO nanostructures

In the present article, electrochemical synthesis of ZnO nanostructures in presence of ultrasonic irradiation is investigated. The ultrasonic bath use for synthesis is calibrated using hydrophone method so that its frequency and acoustic power were obtained. From the results of the experimentation the role of ultrasonic irradiation in synthesis of ZnO nanoparticles is discussed. Diameter of the ZnO nanoparticles produced in the electrolyte was compared and investigated in absence and presence of the ultrasonic irradiation utilizing UV–visible photo-spectrometer. Then electrodeposited ZnO layer on the ITO glass as cathode’s surface in absence and presence of the ultrasonic irradiation were studied by UV–visible photo-spectrometer and field emission scanning electron microscopy (FE-SEM) and the results were compared. FE-SEM micrographs show, higher growth of nanosheets on the cathode electrode in presence of ultrasonic irradiation. Experiment shows synthesis of ZnO nanoparticles in presence of the ultrasonic irradiation happen 10 times faster.     

Growth mechanism and optical property of ZnO nanoparticles synthesized by sonochemical method

ZnO nanoparticles have been synthesized by ultrasonic irradiation of an aqueous-alcoholic/aqueous-alcoholic-ethylenediamine (EDA) solutions of zinc nitrate and sodium hydroxide. ZnO nanoparticles possess hexagonal wurtzite structures and they exhibit special photoluminescence properties with a red-shift of 22 nm in UV emission band. It is found that the ultrasonic irradiation time and the solvents both influence the growth mechanism and optical properties of ZnO nanoparticles. The possible growth mechanism of ZnO nanoparticles formation by sonochemical method has been tried to discuss.     

Using sonochemistry for the fabrication of hollow ZnO microspheres

Hollow ZnO microspheres assembled by nanoparticles have been prepared by a sonochemical synthesis at room temperature using carbon spheres as template. The growth process of the precursor was investigated. The prepared hollow spheres were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM). The diameter of the obtained hollow spheres is about 500 nm, and the walls are composed of numerous ZnO aggregate nanocrystallines with diameters of 90 nm. A possible growth mechanism for the formation of ZnO microspheres has been proposed, in which carbon spheres play a crucial role in the formation of the wurtzite hollow ZnO microspheres. The specific structure of the hollow spheres may find applications in nanoelectronics, nanophotonics and nanomedicine.     

Sonochemical synthesis,formation mechanism,and solar cell application of tellurium nanoparticles

Tellurium inherently tends to form 1-D structures and while the 0-D Te nanostructures have better properties and applications in solar cell. In the present study, 0-D Te nanostructures including rice-like and spherical nanoparticles with the particle size of 15–40 nm were successfully synthesized via a facile sonochemical method. In the absence of ultrasonic irradiation nanorods were produced while performing the reaction under ultrasonic waves (at 200 W for 30 min) led to the formation of nanoparticles. Finally, the efficiency of various as-synthesized Te nanostructures in quantum dot-sensitized solar cells (QDSSCs) were evaluated. Using rice-like nanoparticles led to increase in J_SC, V_OC, FF and η parameters from 1.22, 0.54, 0.49 and 0.32% to 1.57, 0.64, 0.63 and 0.63%, respectively, compared with nanorods.     

Synthesis and characterization of Mg-doped ZnO hollow spheres

Mg-doped ZnO nanoparticles were synthesized by a simple chemical method at low temperature with Mg:Zn atomic ratio from 0 to 7%. The synthesis process is based on the hydrolysis of zinc acetate dihydrate and magnesium acetate tetrahydrate were heated under refluxing at 65 °C using methanol as a solvent. X-ray diffraction analysis reveals that the Mg-doped ZnO crystallizes in a wurtzite structure with crystal size of 5–12 nm. These nanocrystals self-aggregated themselves into hollow spheres of size of 800–1100 nm. High resolution transmission electron microscopy images show that each sphere is made up of numerous nanoparticles of average diameter 5–11 nm. The XRD patterns, SEM and TEM micrographs of doping of Mg in ZnO confirmed the formation of hollow spheres indicating that the Mg²⁺ is successfully substituted into the ZnO host structure of the Zn²⁺ site. Furthermore, the UV–Vis spectra and photoluminescence (PL) spectra of the ZnO nanoparticles were also investigated. The band gap of the nanoparticles can be tuned in the range of 3.36–3.55 eV by the use of the dopants.     

Quantum cutting effect and photoluminescence emission at about 1,000 nm from Er–Yb co-doped ZnO nanoplates prepared by wet chemical precipitation method

ZnO nanoplates with Er-doping concentrations varying in the range from 3 to 7 wt% and co-doped with (Er–Yb) (7 + 7 wt%) were successfully prepared by wet chemical precipitation method. The effects of doping on the structural and optical properties of ZnO nanostructures have been systematically investigated. The structural morphology of the prepared nanostructures was found to change with increasing Er-doping concentrations. The visible photoluminescence and infrared photoluminescence of the prepared nanostructures were measured at room temperature. The intensity of visible emission spectra was found to increase with increasing Er-doping concentrations and was further enhanced for (Er–Yb) co-doped ZnO nanoplate samples. Additionally, Er-doped (7 wt%) and Yb-doped (7 wt%) ZnO nanoplates showed an enhanced emission peak at 950 nm, whereas two enhanced emission peaks at 950 and 980 nm have been found for (Er–Yb)-co-doped (7 + 7 wt%) ZnO nanoplates samples when excited at 310, 365 and 371 nm excitation wavelengths.     

Efficient synthesis of ZnO nanoparticles,nanowalls, and nanowires by thermal decomposition of zinc acetate at a low temperature

ZnO nanoparticles, nanowires, and nanowalls were synthesized rapidly on Si via thermal decomposition of zinc acetate by a modified chemical vapor deposition at a low substrate temperature of 200–250°C for the first time. The diameters of the synthesized nanoparticles and nanowires are around 100 and 30 nm, respectively, and the thickness of nanowalls is around 20 nm. High-resolution transmission electron microscopy shows that the nanowires as well as nanowalls are single-crystalline, and the nanoparticles are highly-textured poly-crystalline structures. Room-temperature photoluminescence spectra of the nanostructures show strong ultraviolet emissions centered at 368–383 nm and weak violet emissions at around 425 nm, indicating good crystal quality. The study provides a simple and efficient route to synthesize ZnO diverse nanostructures at low temperature.     

Synthesis of CdS hollow/solid nanospheres and their chain-structures by membrane technique

CdS hollow/solid nanospheres and their chain-structures were successfully synthesized through supporting liquid membrane (SLM) system with bio-membrane. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV–Vis spectroscopy, and photoluminescence (PL) spectroscopy have been used for the characterization of the products. The average diameters of CdS solid/hollow spheres are about 10, 40 nm, respectively. The wall of the hollow spheres is about 5 nm. CdS products are all cubic face-centered structure with the cell constant a = 5.830 Å. We also explore the morphology, structure and possible synthesis mechanism. A possible template mechanism has been proposed for the production of the hollow CdS nanocrystals, that is, CdS nanoparticles grow along the non-soakage interface between CHCl3 and reactant solution. During this process, the organic functional groups were crucial to the control of crystal morphologies.     

Sonochemical synthesis, photocatalytic activity and optical properties of silica coated ZnO nanoparticles

In this paper, we report the synthesis of silica coated ZnO nanoparticles by ultrasound irradiation of a mixture of dispersion of ZnO, tetraethoxysilane (TEOS), and ammonia in an ethanol-water solution medium. The silica coating layer formed at the initial TEOS/ZnO loading of 0.8 for 60 min ultrasonic irradiation was uniform and extended up to 3 nm from the ZnO surface as revealed from HR-TEM images. Silica coated ZnO nanoparticles demonstrated a significant inhibition of photocatalytic activity against photodegradation of methylene blue dye in aqueous solution. The effects of silica coating on the UV blocking property of ZnO nanoparticles were also studied.     

One-step, template-free route to silver porous hollow spheres and their optical property

Silver porous hollow spheres (SPHS) were fabricated via ultrasonic spray pyrolysis of aqueous solutions containing AgNO₃ and glucose. In the hot spherical liquid droplets, glucose, as reducing agent, reacted with Ag⁺ to form Ag nanoparticles, which subsequently moved to the periphery of the hot liquid droplets to form Ag nanoparticles-glucose hybrid shell. With the temperature further increased, aforementioned Ag nanoparticles melted to form Ag skeleton decorated with unreacted glucose, which converted to SPHS via dissolving unreacted glucose in water. Due to their porous hollow structures, SPHS exhibited a wide Vis-NIR adsorption in the range of 400-1100 nm.     

Influence of two different template removal methods on the micromorphology,crystal structure,and photocatalytic activity of hollow CdS nanospheres

Hollow cadmium sulfide (CdS) nanospheres of about 260 nm average diameters and about 30 nm shell thickness can be easily synthesized via a sonochemical process, in which polystyrene (PS) nanoparticles were employed as templates. In order to remove the PS templates, both etching and calcination were applied in this paper. The influence of the two different template removal methods on the surface micromorphology, crystal structure, and photocatalytic activity of hollow CdS nanospheres was carefully performed a comparative study. Results of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray, FT-IR, thermogravimetric analysis, Brunauer–Emmett–Teller, diffused reflectance spectra, and decolorization experiments showed that the different template removal methods exhibited a significant influence on the surface micromorphology, crystal structure, and photocatalytic activity of hollow CdS nanospheres. The CdS hollow nanospheres as-prepared by etching had pure cubic sphalerite structure, higher –OH content, less defects and exhibited good photocatalytic activity for rhodamine-B, Methylene Blue and methyl orange under UV–vis light irradiation. However, CdS hollow nanospheres obtained by calcination with a hexagonal crystal structure, less –OH content, more defects have shown worse photocatalytic activity. This indicated that surface micromorphology and crystalline phase were mainly factors influencing photocatalytic activity of hollow CdS nanospheres.     

Ion beam synthesis and carrier dynamics of ZnO nanoparticles embedded in a SiO2 matrix

Zinc oxide (ZnO) nanostructures have been synthesized by the implantation of ZnO molecular ions into SiO₂ followed by high temperature thermal annealing. 35 keV ZnO^? ions were implanted to a fluence of 5×10¹⁶ ions/cm² into SiO₂ at room temperature (RT). The implanted sample was annealed in an oxygen environment to allow the growth of ZnO precipitates. In the as-implanted sample, Zn nanoparticles up to 4.5 nm in diameter were observed and were distributed throughout the implanted depth in the SiO₂. The highest concentration of Zn from the implantation was at a depth of 25 nm. During annealing, Zn diffused into the substrate and combined with oxygen to form ZnO. ZnO nanostructures thus formed had diameters up to 8 nm, embedded in SiO₂. Donor-bound exciton (D, X), acceptor-bound exciton (A, X), and donor–acceptor-pair (DAP) transitions were observed in low temperature photoluminescence (PL) measurements on an annealed sample. RT-PL measurement showed band-edge emission in the ultraviolet region with a full width at half maximum of 121 meV. Time-resolved PL measurements performed at 4 K revealed an excitonic lifetime of 160 ps.     

Effect of annealing temperature on optical and electrochemical properties of chitosan–ZnO nanostructure

Chitosan–ZnO nanostructures were prepared by chemical precipitation method using different concentration of zinc chloride and sodium hydroxide solutions. Nanorod-shaped grains with hexagonal structure for samples annealed at 300 °C and porous structure with amorphous morphology for samples annealed at 600 °C were revealed in SEM analysis. X-ray diffraction patterns confirmed the hexagonal phase ZnO with crystallite size found to be in the range of ~24.15–34.83 nm. Blue shift of UV–Vis absorption shows formation of nanocrystals/nanorods of ZnO with marginal increase in band gap. Photoluminescence spectra show that blue–green emission band at 380–580 nm. The chitosan–ZnO nanostructures used on surface of a glassy carbon electrode gives the oxidation peak potential at ~0.6 V. The electrical conductivity of chitosan–ZnO composites were observed at 2.1?×?10^?5 to 2.85?×?10^?5?S/m. The nanorods with high surface area and nontoxicity nature of chitosan–ZnO nanostructures observed in samples annealed at 300 °C were suitable as a potential material for biosensing.     

ZnO spheres and nanorods formation: their dependence on agitation in solution synthesis

ZnO nanostructures including nanorods, dense, and partially hollow spheres were synthesized via a solution synthesis method with temperature ranging from 65 to 95 °C. Scanning electron microscopy (SEM) revealed that the diameter of the spheres is in the range of 200–500 nm. Transmission electron microscopy (TEM) showed that some of the spheres are hollow or partially hollow. Powder X-ray Diffraction (XRD) and TEM-Selected area electron diffraction (SAED) analysis showed that the spheres consist of polycrystalline nanoparticles. It was found for the first time that the agitation during the synthesis plays a critical role on morphology of the ZnO nanostructures formed in solution. The oriented attachment of nanocrystals without agitation during the synthesis could guide the nanocrystals to form an ordered nanorod structure. However, the disordered aggregation of the nanocrystals under shear force resulted in a spherical morphology. It was also found that the composition of spheres is different from that of nanorods: the spheres consist of both ZnO and Zn(OH)₂, but nanorods consist of single-crystal ZnO only. Zn(OH)₂ presented in the spheres could decompose to ZnO by calcination, resulting in the formation of hollow spheres.     

Synthesis and enhanced acetone gas-sensing performance of ZnSnO<Subscript>3</Subscript>/SnO<Subscript>2</Subscript> hollow urchin nanostructures

A kind of novel ZnSnO₃/SnO₂ hollow urchin nanostructure was synthesized by a facile, eco-friendly two-step liquid-phase process. The structure, morphology, and composition of samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption techniques. The results revealed that many tiny needle-like SnO₂ nanowires with the average diameter of 5 nm uniformly grew on the surface of the ZnSnO₃ hollow microspheres and the ZnSnO₃/SnO₂ hollow urchin nanostructures with different SnO₂ content also were successfully prepared. In order to comprehend the evolution process of the ZnSnO₃/SnO₂ hollow urchin nanostructures, the possible growth mechanism of samples was illustrated via several experiments in different reaction conditions. Moreover, the gas-sensing performance of as-prepared samples was investigated. The results showed that ZnSnO₃/SnO₂ hollow urchin nanostructures with high response to various concentration levels of acetone enhanced selectivity, satisfying repeatability, and good long-term stability for acetone detection. Specially, the 10 wt% ZnSnO₃/SnO₂ hollow urchin nanostructure exhibited the best gas sensitivity (17.03 for 50 ppm acetone) may be a reliable biomarker for the diabetes patients, which could be ascribed to its large specific surface area, complete pore permeability, and increase of chemisorbed oxygen due to the doping of SnO₂.     

Microstress,strain, band gap tuning and photocatalytic properties of thermally annealed and Cu-doped ZnO nanoparticles

ZnO nanoparticles and Cu-doped ZnO nanoparticles were prepared by co-precipitation method. Also, a part of the pure ZnO nanoparticles were annealed at 750 °C for 3, 6, and 9 h. X-ray diffraction studies were carried out and the lattice parameters, unit cell volume, interplanar spacing, and Young’s modulus were calculated for all the samples, and also the crystallite size was found using the Scherrer method. X-ray peak broadening analysis was used to estimate the crystallite sizes and the strain using the Williamson–Hall (W–H) method and the size–strain plot (SSP) method. Stress and the energy density were calculated using the W–H method assuming different models such as uniform deformation model, uniform strain deformation model, uniform deformation energy density model, and the SSP method. Optical absorption properties of the samples were understood from their UV–visible spectra. Photocatalytic activities of ZnO and 5 % Cu-doped ZnO were observed by the degradation of methylene blue dye in aqueous medium under the irradiation of 20-W compact fluorescent lamp for an hour.     

Synthesis of ZnO hollow spherical structures with different surface-to-volume ratios

ZnO hollow spherical structures with different surface-to-volume ratios were prepared using solid Zn microspheres as template via a simple oxygen-controlled thermal evaporation approach. The results of scanning electron microscopy testify that ZnO hollow spherical structures with different morphologies can be realized by changing oxygen supply. The corresponding transmission electron microscopy images further reveal that the prepared spherical structures are hollow, and nanorods epitaxially grow from the surface of the sphere shell along the [0001] direction. A series of experiments indicates that the formation of hollow spherical structures involves the oxidization on the surface of Zn microspheres, sublimation of Zn, and growth of ZnO nanorods.     

Synthesis of ZnS hollow nanoneedles via the nanoscale Kirkendall effect

The facile synthesis of one-dimensional II–VI semiconductor hollow nanostructures with sharp tips is of particular interest for their applications in novel nanodevices. In this study, by employing ZnO nanoneedles with lower symmetry structures as self-sacrificed templates, ZnS hollow nanoneedles with homogeneous thickness have been synthesized by a low temperature hydrothermal route through in situ chemical conversion manner and the nanoscale Kirkendall effect. The hollow needlelike structures obtained in the present study can be used as starting materials to create fantastic nanoarchitectures and may have important applications in optoelectronic nanodevices.