Influence of surfactants on structural,morphological, optical and antibacterial properties of SnO2 nanoparticles

Tin oxide (SnO₂) nanoparticles were synthesised using various surfactants of different charges (n‐cetyl trimethyl ammonium bromide, sodium dodecyl sulphate and TRITON X‐100) by the co‐precipitation method. The synthesised nanomaterials were characterised using different techniques to study their structural, surface morphological, optical and anti‐bacterial activities. X‐ray diffraction patterns revealed the formation of a tetragonal rutile structure in pure and surfactants‐aided SnO₂ nanoparticles and the results show good agreement with JCPDS data [41‐1445]. The crystallite size of SnO₂ nanoparticles was found to decrease with the addition of surfactants. Scanning electron microscopy images exhibit spherical shape morphology with an average diameter of 30–75 nm for pure and surfactants‐aided SnO₂ nanoparticles. The band gap energy of the prepared materials was estimated from the UV–visible absorption spectra and a considerable increase in band gap energy was observed in surfactants‐aided SnO₂ nanoparticles (3.487, 3.57, 3.50 and 3.3 eV). The antibacterial activities of the synthesised nanoparticles were studied against Escherichia coli and Staphylococcus aureus bacteria.Inspec keywords: visible spectra, precipitation (physical chemistry), ultraviolet spectra, nanofabrication, tin compounds, X‐ray diffraction, crystallites, titanium compounds, particle size, antibacterial activity, surfactants, nanoparticles, energy gap, scanning electron microscopy, surface morphology, semiconductor materials, optical constants, semiconductor growthOther keywords: SnO₂ , co‐precipitation method, anti‐bacterial activities, X‐ray diffraction patterns, tetragonal rutile structure, spherical shape morphology, band gap energy, sodium dodecyl sulphate surfactant, surface morphology, surfactant‐aided SnO₂ nanoparticles, crystallite size, scanning electron microscopy, UV–visible absorption spectra, Escherichia coli, Staphylococcus aureus bacteria, TRITON X‐100 surfactant, n‐cetyl trimethyl ammonium bromide surfactant     

Effect of doping on structural and optical properties of ZnO nanoparticles: study of antibacterial properties

Sol-gel method was successfully used for synthesis of ZnO nanoparticles doped with 10 % Mg or Cu. The structure, morphology and optical properties of the prepared nanoparticles were studied as a function of doping content. The synthesized ZnO:(Mg/Cu) samples were characterized using XRD, TEM, FTIR and UV-Vis spectroscopy techniques. The samples show hexagonal wurtzite structure, and the phase segregation takes place for Cu doping. Optical studies revealed that Mg doping increases the energy band gap while Cu incorporation results in decrease of the band gap. The antibacterial activities of the nanoparticles were tested against Escherichia coli (Gram negative bacteria) cultures. It was found that both pure and doped ZnO nanosuspensions show good antibacterial activity which increases with copper doping, and slightly decreases with adding Mg.     

Investigations on structural, optical and electrochemical properties of blue luminescence SnO2 nanoparticles

A simple solution approach has been developed to synthesis SnO₂ nanoparticles using polyethylene glycol as stabilizer. X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), UV–Vis absorption spectroscopy, photoluminescence (PL) emission spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the nanoparticles. XRD, HR-TEM and AFM indicate that the SnO₂ nanoparticles correspond to tetragonal crystal structure with size ranges below Bohr’s exciton radius. UV–Vis absorption spectrum showed band gap exhibiting a 1.3 eV shift from that of bulk SnO₂ structures. The blue emission owing to transition of an electron from conduction band to deeply trapped hole in SnO₂ nanoparticles was analyzed using PL spectroscopy. The charge transfer capability had been investigated using CV and EIS in different electrolytes. A detailed exploration on confinement effect that occurred in SnO₂ nanoparticles, mechanism behind visible emission and electron transfer mechanism in different electrolyte was discussed.     

The optoelectronic properties and effect of calcium doping on structural and electrical properties of ZO-Ca aerogel nanoparticles

Calcium-doped ZnO (ZO-Ca) and undoped ZnO nanopowders were synthesized by the sol–gel method. The XRD results indicate that the structural properties of these samples presented hexagonal Wurtzite phase. In addition, the average crystallite size calculated is 37 and 44 nm for an undoped and doped sample, respectively. Further, impedance spectroscopy was investigated to study the calcium doping effect on the electrical behavior of ZnO nanoparticles. The decrease of the exponent s with increasing temperature suggests that the conduction mechanism predominant is the correlated barrier hopping (CBH). The complex impedance analysis of the ZO-Ca samples showed that at low frequency, there is a plateau that get reduced with a temperature which verifies the thermal activation of the conduction mechanism. The obtained results are interesting for understanding the effect of doping on the electronic transport mechanism which is unavoidable to explain the fundamental aspect in various technological applications.

     

The effect of Ce4 + incorporation on structural,morphological and photocatalytic characters of ZnO nanoparticles

We report a simple chemical precipitation method for the preparation of undoped and cerium doped ZnO nanocrystals. The concentration of cerium in the products can be controlled in the range of 0.025–0.125 mol. The structure and chemical compositions of the products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy; energy dispersive spectrum and Fourier transform infrared spectroscopy. The results demonstrate that Ce^4 + ions were successfully incorporated into the lattice position of Zn^2 + ions in ZnO. The morphology of the products was analyzed by field emission scanning electron microscopy and confirmed by high resolution transmission electron microscope analysis. The optical properties of the products were studied by ultraviolet–visible and room temperature photoluminescence measurements. The photoluminescence emission spectra of Ce-doped ZnO showed enhanced visible emissions as a result of 5d → 4f transition of cerium. In particular, a novel photocatalytic activity of the products was assessed using methylene blue. The obtained result reveals that Ce-doped products show higher reduction efficiency for methylene blue than the undoped ZnO.     

Effect of Mn doping concentration on structural,vibrational and magnetic properties of NiO nanoparticles

The Ni_1?xMn_xO (x?=?0.00, 0.02, 0.04 and 0.06) nanoparticles were synthesized by chemical precipitation route followed by calcination at 500?°C for 4?h. The prepared samples were characterized by energy dispersive analysis of X-rays (EDAX), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM). Rietveld refinement of XRD data confirms the structural phase purity and XRD patterns are well indexed to NaCl like rock salt fcc crystal structure with Fm-3m space group. The particle size of Mn doped samples is found to be less than that of pure NiO sample. However, the particle size increases slightly on increasing the Mn concentration due to surface/grain boundary diffusion. The vibrational properties of the synthesized nanoparticles were investigated by Raman and FT-IR spectroscopy. The results of room temperature magnetization (M-H) and temperature dependent magnetization (M-T) measurements are explained with a core-shell model. The synthesized nanoparticles show weak ferromagnetic and super-paramagnetic like behavior at room temperature.     

Insight of yttrium doping on the structural and dielectric characteristics of ZnO nanoparticles

We report on synthesizing rare-earth yttrium oxide-doped ZnO nanoparticles through high-energy planetary milling approach. The impact of varying dopant content in the 3.0, 5.0 to 7.0 wt% range on microstructural, optical and electrical properties of ZnO nanoparticles has been successfully explored. The XRD data showed the existence of a hexagonal wurtzite ZnO phase along with Y₂O₃ impurity peaks, and the SEM micrographs divulge the development of semi-spherical nanoparticles. The incorporation of Y₂O₃ dopant in ZnO lattice has been supported by EDS, XPS and Raman analysis. The frequency and composition dependence of dielectric parameters was investigated and interpreted according to the Maxwell Wagner model. The data revealed non-monotonic dependence of the dielectric constant (ε_r), dielectric loss (tan δ) and AC conductivity and impedance of ZnO with varying dopant content. The variation of the shape of the impedance semicircles and the equivalent circuits between pure and doped ZnO samples prove increased grain boundary resistance due to Y₂O₃ incorporation. The study reveals that Yttrium-doped ZnO nanostructures are possible potential candidates for application in electronic devices if the dopant’s content is controlled.

     

铜纳米粒子的可控制备及其抗菌性能研究

以氯化铜为铜源,水合肼为还原剂,十六烷基三甲基溴化铵(CTAB)为稳定剂,氨水为络合剂,通过液相还原法合成了纳米铜粉。通过改变还原剂浓度制备了4组不同粒径纳米铜粉末,FESEM等表征发现,随着水合肼浓度的降低,纳米铜粉粒径增加。通过肉汤稀释振荡培养法测试纳米铜的最小抑菌浓度,结果表明,随着纳米铜粒径的增加,抗菌性能降低,所合成纳米铜的最小抑菌浓度在750～3000mg/L;初步分析认为铜纳米粒子主要是通过水解或电离出铜离子而发挥抗菌作用。     

Effect of Mn doping on the structural,morphological, optical and magnetic properties of indium tin oxide films

We report on the preparation and characterization of high purity manganese (3–9 wt.%) doped indium tin oxide (ITO, In:Sn = 90:10) films deposited by sol–gel mediated dip coating. X-ray diffraction and selected area electron diffraction showed high phase purity cubic In₂O₃ and indicated a contraction of the lattice with Mn doping. High-resolution transmission electron microscopy depicted a uniform distribution of ∼20 nm sized independent particles and particle induced x-ray emission studies confirmed the actual Mn ion concentration. UV-Vis diffuse reflectance measurements showed band gap energy of 3.75 eV and a high degree of optical transparency (90%) in the 100–500 nm thick ITO films. X-ray photoelectron spectroscopy core level binding energies for In 3d_5/2 (443.6 eV), Sn 3d_5/2 (485.6 eV) and Mn 2p_3/2 (640.2 eV) indicated the In³⁺, Sn⁴⁺ and Mn²⁺ oxidation states. Magnetic hysteresis loops recorded at 300 K yield a coercivity H_c ∼ 80 Oe and saturation magnetization M_s ∼ 0.39 μ_B/Mn²⁺ ion. High-temperature magnetometry showed a Curie temperature T _c > 600 K for the 3.2% Mn doped ITO film.     

Negligible particle-specific antibacterial activity of silver nanoparticles

For nearly a decade, researchers have debated the mechanisms by which AgNPs exert toxicity to bacteria and other organisms. The most elusive question has been whether the AgNPs exert direct "particle-specific" effects beyond the known antimicrobial activity of released silver ions (Ag(+)). Here, we infer that Ag(+) is the definitive molecular toxicant. We rule out direct particle-specific biological effects by showing the lack of toxicity of AgNPs when synthesized and tested under strictly anaerobic conditions that preclude Ag(0) oxidation and Ag(+) release. Furthermore, we demonstrate that the toxicity of various AgNPs (PEG- or PVP- coated, of three different sizes each) accurately follows the dose-response pattern of E. coli exposed to Ag(+) (added as AgNO(3)). Surprisingly, E. coli survival was stimulated by relatively low (sublethal) concentration of all tested AgNPs and AgNO(3) (at 3-8 μg/L Ag(+), or 12-31% of the minimum lethal concentration (MLC)), suggesting a hormetic response that would be counterproductive to antimicrobial applications. Overall, this work suggests that AgNP morphological properties known to affect antimicrobial activity are indirect effectors that primarily influence Ag(+) release. Accordingly, antibacterial activity could be controlled (and environmental impacts could be mitigated) by modulating Ag(+) release, possibly through manipulation of oxygen availability, particle size, shape, and/or type of coating.     

Effect of vanadium and tungsten doping on the structural,optical, and electronic characteristics of TiO2 nanoparticles

Journal of Materials Science: Materials in Electronics - Nanoparticles of TiO2 and Ti0.97M0.03O2 (M≡V, W) samples were produced using sol–gel procedure. Utilizing synchrotron x-ray...     

Ultrafine dispersed CuO nanoparticles and their antibacterial activity

Copper oxide nanoparticles with a particle size ranging from 80 to 160 nm were prepared by a wet chemical procedure. Copper carbonate hydroxide and sodium hydroxide were used as raw materials. Copper hydroxide was generated as a precursor which was thermally decomposed to CuO nanoparticles. The nanoparticles were characterised using atomic force microscopy, X-ray diffraction and UV-visible spectrometry. The nanoparticles were tested for antibacterial activity against Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella paratyphi and Shigella strains.     

Effects of co-doped Li+ ions on luminescence of CaWO4:Sm3+ nanoparticles

CaWO₄, CaWO₄:Sm³⁺ and CaWO₄:(Sm³⁺, Li⁺) nanoparticles were synthesized by the precipitation method with addition of PEG 200. The X-ray diffraction patterns show that the obtained samples have a pure tetragonal phase. The CaWO₄ sample shows an emission peak at 418 nm originating from the charge-transfer transitions within the WO₄ ^2? complex. CaWO₄:Sm³⁺ and CaWO₄:(Sm³⁺, Li⁺) samples show emission peaks originating from the f–f forbidden transitions of the 4f electrons of Sm³⁺ ions. The charge compensator of Li⁺ can enhance the emission intensity effectively. It is found that the emission intensity of CaWO₄:(3 mol% Sm³⁺, 4 mol% Li⁺) phosphor is about double that of CaWO₄:3 mol% Sm³⁺ phosphor.     

聚乙烯亚胺包埋无色纳米银抗菌剂制备及协同抗菌效果研究

以高枝化聚乙烯亚胺(PEI)为稳定剂,硼氢化钠为还原剂,利用化学还原法制备了纳米银抗菌剂。探讨了温度、PEI与Ag+的摩尔比对纳米银抗菌剂合成的影响,利用紫外分光光度法及扫描电镜对合成纳米银抗菌剂进行了表征,利用抑菌圈实验分别对纳米银及PEI进行了抑菌性能测试,筛选出稳定性好抑菌性强的纳米银抗菌剂制备工艺。实验结果表明,在45℃,PEI与Ag+的摩尔配比在2∶1~0.6∶1条件下能制备无色透明且抑菌性强的具有核壳结构的纳米银抗菌剂,PEI对纳米银抗菌剂具有协同作用。