Zn0@ZnS Core‐Shell Nanoparticles via Oxidation of Intermediate Zn0 Nanoparticles

Zn⁰@ZnS core‐shell nanoparticles were prepared via reduction of ZnCl₂ to Zn⁰ nanoparticles and subsequent partial oxidation with elemental sulfur. The intermediate, highly reactive Zn⁰ nanoparticles were obtained by sodium naphthalenide ([NaNaph]) reduction of ZnCl₂ in tetrahydrofuran (THF). After centrifugation, the Zn⁰ nanoparticles were redispersed in a solution of sulfur in toluene and oxidized by subsequent heating to reflux. According to electron microscopy (HRTEM, HAADF‐STEM), the Zn⁰@ZnS core‐shell nanoparticles exhibit a mean outer diameter of 12 ± 4 nm, consisting of an inner Zn⁰ core (8 nm in diameter) and a ZnS shell (2 nm in diameter). HRTEM and XRD confirm the crystallinity of both core and shell. The Zn⁰@ZnS nanostructure shows synergistic properties of core and shell: the ZnS layer efficiently passivates the reactive Zn⁰ metal core against oxidation, whereas the optical properties point to dominating metallic behavior of the Zn⁰ metal core despite of the ZnS shell.     

Methylviologen-mediated electrochemical synthesis of silver nanoparticles via the reduction of AgCl nanospheres stabilized by cetyltrimethylammonium chloride

Efficient synthesis of silver nanoparticles stabilized by cetyltrimethylammonium cations (Ag@CTA⁺) is carried out in aqueous medium by methylviologen-mediated electroreduction of silver chloride nanospheres stabilized by surface-active CTA⁺ cations (AgCl@CTA⁺, diameter ~330 nm), on a glassy carbon electrode at potentials of the MV²⁺/MV^?+ redox couple. The nanospheres AgCl@CTA⁺ can be reduced immediately on the electrode at a low rate and the resulting metal is deposited on the electrode. In the mediated reduction, the metal is not deposited on the cathode but the quantitative reduction of AgCl to Ag@CTA⁺ nanoparticles proceeds completely in solution volume at the theoretical charge. In aqueous solution, the nanoparticles are positively charged (electrokinetic (zeta) potential is +74.6 mV), their characteristic absorption maximum is at 423 nm and the average hydrodynamic diameter is 77 nm. Isolated Ag@CTACl nanoparticles have the size of 39 ± 15 nm. The preferential form of metal nanoparticles is sphere with the diameter of 34 ± 24 nm; nanorods are also obtained in small amounts (4%); the average size of metal grains is 8–16 nm.     

Removal of dithioterethiol (DTT) from water by membranes of cellulose acetate (AC) and AC doped ZnO and TiO2 nanoparticles

Dithioterethiol (DTT) is a typical example of substances that contain sulfur with adverse effects on human health. Membranes-based cellulose acetate is used for the separation processes of thiols after the addition of ZnO and TiO₂ nanoparticles. The measurement of permeability allows us to estimate the efficiency of membrane cleaning. The permeability increases from 8.82 L.h^?1.m^?2.bar^?1 for CA membrane to 20.77 L.h^?1.m^?2.bar^?1 for CA-TiO₂ and 21.96 L.h^?1.m^?2.bar^?1 for CA-ZnO membranes. For the permeability values of DTT, we noted that the CA-ZnO membrane has the highest permeability (50.66 L.h^?1.m^?2.bar^?1). The CA-ZnO membrane changes from nanofiltration to ultrafiltration membrane. On the other hand, for the CA-TiO₂ modified membrane, the permeability decreases to 6.00 L.h^?1.m^?2.bar^?1. The CA-TiO₂ membrane is in the category of reverse osmosis membranes. This variation is explained by the interaction between nanoparticles and DTT. The contact angles of the incorporated membranes decrease progressively with the addition of TiO₂ or ZnO-NPs. The low contact angle with water means high hydrophilicity, indicated that the addition of TiO₂ and ZnO improved the hydrophilicity of the membranes. The CA membrane had the highest contact angle with water of 92.64 ± 1.5°. After the addition of 0.1 g of TiO₂ or ZnO, the contact angle of CA-TiO₂ and CA-ZnO was reduced to 86.7 ± 0.2° and 70.51 ± 1.5°, respectively. Both TiO₂ and ZnO caused strong hydrophilicity of membranes. From the elimination rates of DTT, it is concluded that there are optimal conditions of (1) Pressure P = 2 bars, (2) pH = 10 and (3) DTT concentration = 2 mM.     

Size-controllable synthesis of spherical ZnO nanoparticles: Size- and concentration-dependent resonant light scattering

A new and simple direct precipitation method assisted with ultrasonic agitation was proposed for the preparation of spherical ZnO nanoparticles. The size of the ZnO nanoparticles, 10 nm to 85 nm, was tuned through controlling the calcination temperature and changing the ratio of the reactants. The resonant light scattering (RLS) of the ZnO nanoparticles dispersed/suspended in aqueous solution of Triton X-100 was studied under room temperature. It was found that the ZnO nanoparticles of different size or concentration all have a characteristic RLS peak at 387 nm. Under optimal conditions, the RLS intensity was proportional to the ZnO concentration in the range of 7.3 × 10^?8–1 × 10^?4 mol L^?1, while the cubic root of the RLS intensity was found to be proportional to the size of ZnO nanoparticles. Further, the quantitative relationship of the size of the ZnO nanoparticles versus the calcination temperature was derived, and this could be used to forecast/control the nano-size in the nano-ZnO preparation.     

The synthesis of ZnS hollow nanospheres with nanoporous shell

ZnS hollow nanospheres with nanoporous shell were successfully synthesized through the evolvement of ZnO nanospheres which were synthesized by hydrothermal method with poly (sodium-p-styrene sulfonate) (PSS) as surfactant at low temperature. The as-synthesized samples were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), UV/vis spectrum and N₂ adsorption. The results showed that the shell of as-synthesized ZnS hollow structure was composed of many fine crystallites and had a nanoporous structure with pore diameter about 4 nm demonstrated by N₂ adsorption/desorption isotherm. The sample possessed efficiency of photocatalytic degradation on X-containing (X=Cl, Br, I) organic pollutants.     

Co doped ZnO nanowires as visible light photocatalysts

High aspect ratio cobalt doped ZnO nanowires showing strong photocatalytic activity and moderate ferromagnetic behaviour were successfully synthesized using a solvothermal method and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), vibrating sample magnetometry (VSM) and UV–visible absorption spectroscopy. The photocatalytic activities evaluated for visible light driven degradation of an aqueous methylene orange (MO) solution were higher than for Co doped ZnO nanoparticles at the same doping level and synthesized by the same synthesis route. The rate constant for MO visible light photocatalytic degradation was 1.9·10⁻³ min⁻¹ in case of nanoparticles and 4.2·10⁻³ min⁻¹ in case of nanowires. We observe strongly enhanced visible light photocatalytic activity for moderate Co doping levels, with an optimum at a composition of Zn_0.95Co_0.05O. The enhanced photocatalytic activities of Co doped ZnO nanowires were attributed to the combined effects of enhanced visible light absorption at the Co sites in ZnO nanowires, and improved separation efficiency of photogenerated charge carriers at optimal Co doping.     

Biosynthesis of zinc oxide nanoparticles using Euphorbia milii leaf constituents: Characterization and improved photocatalytic degradation of methylene blue dye under natural sunlight

A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m²/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm³/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm^?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications.     

Preparation and properties of nitrogen-containing hollow carbon nanospheres by pyrolysis of polyaniline-lignosulfonate composites

Polyaniline-lignosulfonate composite hollow spheres were synthesized by using one-step unstirred polymerization of aniline in the presence of lignosulfonate. Novel nitrogen-containing hollow carbon nanospheres were prepared by direct pyrolysis of the polyaniline-lignosulfonate composite spheres at different temperatures under a nitrogen atmosphere. Thermal behavior of the polyaniline-lignosulfonate composite spheres was studied by TG-DTG, FTIR and element analyze instruments. The resultant carbon spheres were characterized by SEM, XRD and nitrogen adsorption-desorption measurement. It was found that the pyrolysis products of the polyaniline-lignosulfonate composite spheres were made up of uniform hollow carbon nanospheres with an average diameter of 135 nm. Furthermore, the hollow carbon nanospheres exhibit high BET surface area range from 381.6 m² g⁻¹ to 700.2 m² g⁻¹. The hollow carbon nanospheres could be used as adsorbents of papain. The papain adsorption capacity for the carbon spheres prepared at 1200 °C was up to 1161 mg g⁻¹ at an initial papain concentration of 10 mg mL⁻¹ at 25 °C.     

Different morphologies of ZnO nanostructures via polymeric complex sol–gel method: synthesis and characterization

Various morphologies of ZnO nanostructures, such as nanoparticles, nanorods and nanoflowers have been achieved controllably by polymeric sol–gel method. In this approach, zinc nitrate Zn(NO₃)₂·6H₂O, citric acid and ethylene glycol were used as the source of Zn²⁺, the chelating agent and the solvent agent, respectively. The microstructure of the ZnO nanostructures was characterized by X-ray diffractometry, scanning electron microscopy with the energy dispersive X-ray spectroscopy, transmission electron microscopy, thermogravimetric analysis and Fourier transform infrared spectroscopy. The effect of ethylene glycol to citric acid mole ratio on the morphology and structure of the products was discussed. The ZnO nanoparticles with diameter between 24 ± 2 nm was obtained with EG:CA mole ratio equal to 2:1. The optical properties of as-obtained power were investigated by ultraviolet–visible spectroscopy.     

Laux‐type Oxidation of In0 Nanoparticles to In2O3 Retaining Particle Size and Colloidal Stability

As a conceptual study, In⁰ nanoparticles are obtained by NaBH₄‐driven reduction of InCl₃ · 4H₂O and transferred from a polar/hydrophilic diethylene glycol phase to a non‐polar hydrophobic dodecane phase for purification and stabilization. Finally, the In⁰ nanoparticles are oxidized via a Laux‐like reaction with nitrobenzene to In₂O₃ nanoparticles. The challenge of the reaction is to perform the final oxidation to In₂O₃ under mild conditions with the colloidal stability, particle size and particle size distribution of the initial In⁰ nanoparticles retained. To this concern, the mean diameter of the initial In⁰ nanoparticles changed from 11(1) to 14(2) nm of the oxidized In₂O₃ nanoparticles. Such multi‐step reaction, including reduction, nucleation, phase transfer, exchange of surface capping and oxidation are of increasing importance for nanoparticles. Especially, Laux‐type conditions with nitrobenzene as a molecular oxidizing agent of nanoparticles have not been used till now. Particle size, size distribution and chemical composition of the In⁰ and In₂O₃ nanoparticles are analyzed by DLS, SEM, XRD, FT‐IR and HRTEM.     

Preparation and characterization of Al and Mn doped ZnO (ZnO: (Al,Mn)) transparent conducting oxide films

This paper presents the electro-optical, chemical and structural properties of doped-ZnO films deposited by DC-reactive magnetron sputtering at room temperature using the bi-dopant Al and Mn. A minimum resistivity of 3.46×10⁻⁴ Ω cm, exceeding 75.0% average transmittance (380–800 nm), and fundamental band gap of 3.48±0.01 eV have been obtained. XPS analyses show that Zn uniformly remains in the valence state of Zn²⁺; all of the Al and a little amount of Mn with valence state of Mn⁴⁺ are supposed to have donor effect, while dominant Mn²⁺ will induce to form more oxygen vacancies and this proposal has been verified by O 1s XPS results. It has been concluded that the presence of more oxygen vacancies will attenuate the effect of hybridization of p–d orbitals in the matrix of ZnO. It has been found that all the as-deposited films have c-axis preferred orientation with flat and smooth surface (RMS surface roughness is of the order of ∼3 nm over 5×5 μm² area).     

Low Temperature Preparation of 3D Solid and Hollow ZnS Nanosphere Self-Assembled from Nanoparticles by Varying Sulfur Source

In this work, we report a facile hydrothermal method for the preparation of three dimensional hollow ZnS nanostructures, using Zinc bis(salicyle aldehitato), Zn(Sal)₂, thioacetamide (TAA) and thioglycolic acid (TGA) as Zn²⁺, sulfur source and capping agent, respectively. The ZnS solid and hollow sphere was produced from the self-assembly of nanoparticles with diameters of 11 ± 2 nm with TGA and TGA, TAA, respectively. Furthermore, with changing zinc precursor from Zn(Sal)₂ to zinc acetate [Zn(OAC)₂], ZnS nanorods were obtained. The products were characterized by XRD, SEM, TEM, selected area electron diffraction, and FT-IR spectra. The influence of surfactant (Polyethylene glycol) on the morphology of the products was also investigated. Possible formation mechanism and optical properties of these architectures were also reported.     

SiO2 nanospheres with tailorable interiors by directly controlling Zn and NH3·H2O species in an emulsion process

SiO₂ nanospheres with tailorable interiors were synthesized by a facile one-spot microemulsion process using TEOS as silica source, wherein cyclohexane including triton X-100 and n-octanol as oil phase and Zn²⁺ or NH₃·H₂O aqueous solution as dispersive phase, respectively. The products were characterized by Scanning Electron Microscopy, Transmission Electron Microscopy and X-ray Powder Diffraction. It was suggested that the as-synthesized silica nanospheres possessed grape-stone-like porous or single hollow interior, and also found that the ammonia dosage and aging time played key roles in controlling the size and structure of silica nanospheres. Furthermore, the comparative results confirmed that in-situ zinc species [ZnO/Zn(OH)₂] acted as the temporary templates to construct grape-stone-like interior, and a simultaneously competing etching process occurred owing to the soluble Zn(NH₃)₄²⁺ complex formation while the additional excessive ammonia was introduced. With the aging time being extended, the in-situ nanocrystals tended to grow into bigger ones by Ostwald Ripening, producing single hollow interior.     

Porous α-Fe2O3 hollow microspheres and their application for acetone sensor

Porous α-Fe₂O₃ hollow microspheres were synthesized through a simple and efficient carbon sphere template method. The samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and N₂ adsorption-desorption. Structural characterization indicated that as-prepared α-Fe₂O₃ hollow microspheres had porous structure with around 200 nm in diameter and thin shell about 10 nm thick. The average pore size and Brunauer-Emmett-Teller specific surface area of α-Fe₂O₃ hollow microspheres were 6.5 nm and 111.6 m²/g, respectively. The gas sensing behavior investigation showed that as-synthesized α-Fe₂O₃ hollow microspheres exhibited very good gas sensing property to acetone vapor.     

Green approach to synthesize nano zinc oxide via Moringa oleifera leaves for enhanced anti-oxidant,anti-acne and anti-bacterial properties for health & wellness applications

This article explores green synthesis as a strategic and sustainable route to fabricate potent zinc oxide nanoparticles. Natural green based antibacterial agents and alternatives are being introduced in the market however there is a dearth in green approach moringa based zinc oxide nanoparticles in personal care products and establishing efficacy. Moringa oleifera comprises various phytochemicals that act as non-toxic stabilizing and reducing agents. Green synthesized ZnO nanoparticles (GsZnO-Nps) were investigated for their morphological and physicochemical properties using various advanced characterizing techniques. The hexagonal wurtzite structure of GsZnO-Nps is determined by X-ray diffractometry (XRD), the average crystallite size is 13.82 nm, total crystallinity was 95.91 % and high specific-surface-area is 77.38 m²/g. Scanning Electron Microscope (SEM) revealed the formation of spherical nanoparticles having a diameter of 50 nm. UV–vis spectrum shows high bandgap energy of 3.36 eV. Results have shown that antioxidant efficacy of GsZnO-Nps is significantly higher than AR-Grade ZnO, evaluated by using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay. Half-maximal inhibitory concentration (IC₅₀) of GsZnO-Nps was 21.72 µg/mL and AR-Grade ZnO was 345.57 µg/mL. GsZnO-Nps (0.0183 g/mL) shows robust anti-acne efficacy against Cutibacterium acne (C. acne) organism which estimated by ZOI technique, have average ZOI of 33 mm, with standard error 0.577 mm. Antibacterial efficacy of GsZnO-Nps was established at different concentrations (10, 50, 100, and 200 µg/mL) against Gram-positive and Gram-negative pathogens by zone-of-inhibition (ZOI) method with respect to standard drugs. GsZnO-Nps at 200 µg/mL exhibits high ZOI of 26.75 mm against Escherichia coli (E. coli) and ZOI of 30 mm against Staphylococcus aureus (S. aureus) organisms respectively which is comparatively higher or equal to standard drugs. The minimum inhibitory concentration (MIC) of GsZnO-Nps is 500 µg/mL to inhibit the microbe's growth. GsZnO-Nps established the added benefits of moringa phytochemicals and is an excellent approach to developing eco-friendly and multi-functional versatile products having strong antioxidants, anti-acne and advanced antibacterial efficacy for numerous industrial applications like cosmetic, health hygiene products, drugs, therapeutic etc.     

Sonochemical Preparation of Hierarchical ZnO Hollow Spheres for Efficient Dye‐Sensitized Solar Cells

Hierarchical ZnO hollow spheres (400–500 nm in diameter) consisting of ZnO nanoparticles with a diameter of approximately 15 nm have been successfully prepared by a facile and rapid sonochemical process. The formation of hierarchical ZnO hollow spheres is attributed to the oriented attachment and subsequent Ostwald ripening process according to time‐dependent experiments. The as‐prepared ZnO hollow spheres are used as a photoanode in dye‐sensitized solar cells and exhibit a highly efficient power conversion efficiency of 4.33 %, with a short‐circuit current density of 9.56 mA cm^?2, an open‐circuit voltage of 730 mV, and a fill factor of 0.62 under AM 1.5 G one sun (100 mW cm^?2) illumination. Moreover, the photovoltaic performance (4.33 %) using the hierarchical ZnO hollow spheres is 38.8 % better than that of a ZnO nanoparticle photoelectrode (3.12 %), which is mainly attributed to the efficient light scattering for the former.     

Structural,optical and photoluminescence properties of Zn<Subscript>1−x</Subscript>Ce<Subscript>x</Subscript>O (x = 0, 0.05 and 0.1) nanoparticles by sol–gel method annealed under Ar atmosphere

Ce doped ZnO nanoparticles (Zn_1−xCe_xO, x = 0.0, 0.05 and 0.1) have been synthesized by sol–gel method at annealing temperature of 500 °C for 1 h under Ar atmosphere. The synthesized samples have been characterized by powder X-ray diffraction (XRD), energy dispersive X-ray studies, UV–Visible spectrophotometer and fourier transform infrared (FTIR) spectroscopy. The XRD measurements indicate that the prepared nanoparticles have a hexagonal wurtzite structure and CeO₂ crystallites. The calculated average crystalline varied from 21.97 to 15.62 nm with increase in Ce concentrations. The increase in lattice parameters reveals the substitution of Ce into ZnO lattice. The presence of functional groups and the chemical bonding is confirmed by FTIR spectra. PL spectra of the Zn_1−xCe_xO system show that the shift in near band edge emission from 386 to 363 nm and a shift in blue band emission from 517 to 485 nm which confirms the substitution of Ce into the ZnO lattice.     

Ratiometric fluorescent Zn chemosensor constructed by appending a pair of carboxamidoquinoline on 1,2-diaminocyclohexane scaffold

By appending a pair of carboxamidoquinoline pendants onto 1,2-diaminocyclohexane scaffold via N-alkylation, multifunctionalized ACAQ was designed and synthesized as a water soluble fluorescent ratiometric chemosensor for Zn²⁺. In 50% aqueous methanol buffer pH 7.4 solution, upon excitation at 316 nm, ACAQ (5 μM) displayed a selective ratiometric fluorescence changes with a shift from 410 to 490 nm in response to the interaction with Zn²⁺. After binding with 1 equiv of Zn²⁺, ACAQ exhibited a 12-fold enhancement in I₄₉₀/I₄₁₀ characterized by a clear isoemissive point at 440 nm. The metal sensor binding mode was established by Job’s plot and the combined fluorescence and ¹H NMR spectroscopic method. The selectivity of the probe toward biological relevant cations and transition metal ions was proven to be good. In addition, the interference caused by Cu²⁺ and Cd²⁺ in the quantitation of Zn²⁺ can be completely eliminated by the use of diethyldithiocarbamate as the screening agent. Exploitation of ACAQ as the sensing probe, ratiometric determination of Zn²⁺ with the limit of detection (LOD) at 28.3 nm can be realized. In addition, the unique responsive properties of the probe toward Fe³⁺ and Zn²⁺ were used to construct a fluorescent switch. The membrane permeability of ACAQ to living cells and bio-imaging of Zn²⁺ were demonstrated.     

In situ thermo-TOF-SIMS study of thermal decomposition of zinc acetate dihydrate

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used for an in situ thermal decomposition study of Zn(CH₃COO)₂·2H₂O forming ZnO nanoparticles. TOF-SIMS spectra were recorded at regular temperature intervals of 25 °C in positive and negative detection modes in a dynamic thermal process. Controlled heating (5 °C min⁻¹) of Zn(CH₃COO)₂·2H₂O was also carried out using thermogravimetric analysis (TGA) in an oxygen atmosphere (20 ml min⁻¹). Nearly spherical ZnO nanoparticles with no agglomeration and a narrow size distribution (diameter ∼50 nm) were observed, which were characterized using scanning electron microscopy, transmission electron microscopy and x-ray diffraction. In situ thermo-TOF-SIMS was used to monitor the ⁶⁴Zn⁺ and ⁶⁶Zn⁺ ion abundances as a function of temperature, which showed a similar profile to that observed for weight loss in TGA during decomposition. Based on the experimental results, a possible decomposition mechanism for the formation of ZnO is proposed. Copyright © 2004 John Wiley & Sons, Ltd.     

Stimulated emission cross sections and temperature-dependent spectral shifts of neutral nitrogen-vacancy centers in diamonds

The neutral nitrogen-vacancy (NV⁰) defects in diamond are photostable color centers, suitable for a wide range of applications in science and engineering. However, the photophysical properties of the centers have not yet been fully characterized. This work measured the stimulated emission cross sections of NV⁰ in a single-crystal diamond by two-photon excitation of its matrix at 344 nm. From the measured photoluminescence spectrum and the fluorescence lifetime of 20 ± 1 ns, we determined a peak stimulated emission cross section of 1.43 ± 0.07 × 10⁻¹⁷ cm² at 650 nm for the NV⁰ centers. In addition, we have also examined the thermal shifts of the zero-phonon line of NV⁰ centers in nanoscale diamonds (~100 nm in diameter) over the temperature range of 30–120°C. A temperature measurement sensitivity of 0.2 K·Hz^−1/2 was achieved, which is about two-fold better than that of NV⁻, despite that the fluorescence intensity of NV⁰ is about six-fold lower than that of NV⁻ in the same nanoparticles. The result is attributed to the smaller electron–phonon coupling strength of the neutral center, compared with its negatively charged counterpart.