Thermal calcination-based production of SnO2 nanopowder: an analysis of SnO2 nanoparticle characteristics and antibacterial activities

SnO2 nanoparticle production using thermal treatment with tin(II) chloride dihydrate and polyvinylpyrrolidone capping agent precursor materials for calcination was investigated. Samples were analyzed using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), diffuse UV-vis reflectance spectra, photoluminescence (PL) spectra and the electron spin resonance (ESR). XRD analysis found tetragonal crystalline structures in the SnO2 nanoparticles generated through calcination. EDX and FT-IR spectroscopy phase analysis verified the derivation of the Sn and O in the SnO2 nanoparticle samples from the precursor materials. An average nanoparticle size of 4–15.5 nm was achieved by increasing calcination temperature from 500 °C to 800 °C, as confirmed through TEM. The valence state and surface composition of the resulting nanoparticle were analyzed using XPS. Diffuse UV-vis reflectance spectra were used to evaluate the optical energy gap using the Kubelka-Munk equation. Greater calcination temperature resulted in the energy band gap falling from 3.90 eV to 3.64 eV. PL spectra indicated a positive relationship between particle size and photoluminescence. Magnetic features were investigated through ESR, which revealed the presence of unpaired electrons. The magnetic field resonance decreases along with an increase of the g-factor value as the calcination temperature increased from 500 °C to 800 °C. Finally, Escherichia coli ATCC 25922 Gram (–ve) and Bacillus subtilis UPMC 1175 Gram (+ve) were used for in vitro evaluation of the tin oxide nanoparticle’s antibacterial activity. This work indicated that the zone of inhibition of 22 mm has good antibacterial activity toward the Gram-positive B. subtilis UPMC 1175

Comprehensive study on morphological, structural and optical properties of Cr2O3 nanoparticle and its antibacterial activities

Chromium (III) oxide (Cr2O3) nanoparticles are generated by thermal treatment (calcination) of precursor materials such as chromium nitrate along with a poly (vinyl pyrrolidone) capping agent. The samples produced were characterised by various techniques, including X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR). Examination results obtained from XRD showed that Cr2O3 nanoparticles exhibit hexagonal crystalline structures, with the presence of Cr and O in these novel materials being confirmed by results of analyses of both EDX and FT-IR. Results of TEM have pointed out that the average nanoparticle size was noticeably increased from 28 to 46 nm in relation to increase of calcination temperature of a range between 500 and 800 °C. The surface composition and valence state of the produced nanoparticles were examined by X-ray photoelectron spectroscopy (XPS), the optical energy gap has been evaluated using UV–visible reflectance spectra with the help of Kubelka–Munk equation. The energy band gap had a reversely proportional relationship with calcination temperature with a reduction in energy band gap from 3.12 to 3.01 eV. Photoluminescence (PL) spectra indicated an increase in photoluminescence with increasing particle size. The antibacterial activity of the Cr2O3 nanoparticles was evaluated in-vitro using gram-negative Escherichia coli ATCC 25922 and gram-positive Bacillus subtilis UPMC 1175

The effect of PVP concentration on particle size, morphological and optical properties of cassiterite nanoparticles

Different concentrations of polyvinylpyrrolidone (PVP) have been successfully employed to prepare high purity tetragonal cassiterite nanoparticles, and control the growth of particle size. The effect of PVP on the structural, morphological, size, composition, and optical properties of the prepared cassiterite nanoparticles has been investigated. It has been found that various characteristics of tetragonal cassiterite nanoparticles could be optimized by simply changing the values of PVP. The pure tetragonal cassiterite nanoparticles have been produced at the optimum calcination temperature. The XRD and SEM results indicated the structural and morphological properties of the tetragonal cassiterite nanoparticles, respectively. The particles' size and their distribution have been displayed by TEM images. The composition phase and the surface composition of the prepared samples have been evaluated via FTIR and XPS, respectively. The optical properties of the prepared tetragonal cassiterite nanoparticles have been studied using UV-vis and PL spectroscopy. Outcomes cassiterite nanoparticles are useful for antibacterial activity and application of solar energy

Down-top nanofabrication of binary (CdO)x (ZnO)1–x nanoparticles and their antibacterial activity

In the present study, binary oxide (cadmium oxide [CdO])x (zinc oxide [ZnO])1–x nanoparticles (NPs) at different concentrations of precursor in calcination temperature were prepared using thermal treatment technique. Cadmium and zinc nitrates (source of cadmium and zinc) with polyvinylpyrrolidone (capping agent) have been used to prepare (CdO)x (ZnO)1–x NPs samples. The sample was characterized by X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. XRD patterns analysis revealed that NPs were formed after calcination, which showed a cubic and hexagonal crystalline structure of (CdO)x (ZnO)1–x NPs. The phase analysis using EDX spectroscopy and FTIR spectroscopy confirmed the presence of Cd and Zn as the original compounds of prepared (CdO)x (ZnO)1–x NP samples. The average particle size of the samples increased from 14 to 33 nm as the concentration of precursor increased from x=0.20 to x=0.80, as observed by TEM results. The surface composition and valance state of the prepared product NPs were determined by X-ray photoelectron spectroscopy (XPS) analyses. Diffuse UV–visible reflectance spectra were used to determine the optical band gap through the Kubelka–Munk equation; the energy band gap was found to decrease for CdO from 2.92 to 2.82 eV and for ZnO from 3.22 to 3.11 eV with increasing x value. Additionally, photoluminescence (PL) spectra revealed that the intensity in PL increased with an increase in particle size. In addition, the antibacterial activity of binary oxide NP was carried out in vitro against Escherichia coli ATCC 25922 Gram (-ve), Salmonella choleraesuis ATCC 10708, and Bacillus subtilis UPMC 1175 Gram (+ve). This study indicated that the zone of inhibition of 21 mm has good antibacterial activity toward the Gram-positive B. subtilis UPMC 1175

Host-Guest Chemistry Meets Electrocatalysis: Cucurbit[6]uril on a Au Surface as a Hybrid System in CO2 Reduction.

The rational control of forming and stabilizing reaction intermediates to guide specific reaction pathways remains to be a major challenge in electrocatalysis. In this work, we report a surface active-site engineering approach for modulating electrocatalytic CO2 reduction using the macrocycle cucurbit[6]uril (CB[6]). A pristine gold surface functionalized with CB[6] nanocavities was studied as a hybrid organic-inorganic model system that utilizes host-guest chemistry to influence the heterogeneous electrocatalytic reaction. The combination of surface-enhanced infrared absorption (SEIRA) spectroscopy and electrocatalytic experiments in conjunction with theoretical calculations supports capture and reduction of CO2 inside the hydrophobic cavity of CB[6] on the gold surface in aqueous KHCO3 at negative potentials. SEIRA spectroscopic experiments show that the decoration of gold with the supramolecular host CB[6] leads to an increased local CO2 concentration close to the metal interface. Electrocatalytic CO2 reduction on a CB[6]-coated gold electrode indicates differences in the specific interactions between CO2 reduction intermediates within and outside the CB[6] molecular cavity, illustrated by a decrease in current density from CO generation, but almost invariant H2 production compared to unfunctionalized gold. The presented methodology and mechanistic insight can guide future design of molecularly engineered catalytic environments through interfacial host-guest chemistry

Untersuchung von Photoionisationsprozessen in den 3d –Übergangsmetalverbindungen FeCl2 FeBr2 und CoCl2

Um die intra-atomare und interatomare Wechselwirkung im Vergleich der Molekülspektren mit den korrespondierenden Atom auf der einen Seite und mit den Festkörperspektren auf der anderen Seite besser zu verstehen, ist eine detaillierte Analyse der elektronischen und magnetischen Struktur notwendig. Der Schlüssel zu den magnetischen und elektronischen Eigenschaften dieser Verbindungen sind die 3d-Elektronen. Sie können durch die Anregung von 3p-Elektronen in die 3d-Schale oder durch eine direkte Anregung des 3p-Elektrons analysiert werden. Die 3p-Photoabsorptions-Spektren von FeCl2, FeBr2 und CoCl2 weisen ein hohes Maß an Gleichheit auf, wenn sie mit den korrespondierenden Atomarenspektren verglichen werden. Der Vergleich der 3p-Photoelektronen-Spektren von FeCl2, FeBr2 und CoCl2 mit den korrespondierenden 3p-Photoelektronen-Spektren von atomarem Fe und Co zeigt einen deutlichen Einfluss der Molekülbindung auf das Valenzelektron. Eine weitere Untersuchung des Einflusses der Molekülbindung auf das Valenzelektron wurde durch den Vergleich der 3p mit den 2p Photoelektron Daten von FeCl2 durchgeführtIn order to have a better understanding of the interplay of intra-atomic and interatomic interaction in the comparison of the molecular spectra with the corresponding atomic on the one hand and with the solid spectra on the other hand, a detailed analysis of the electronic and magnetic structure is absolutely needed. The key of the magnetic and electronic properties of these compound systems are the 3d electrons. Analysis of these can be accomplished by exciting 3p electrons into 3d shell or by a direct exciting of the 3d electron. 3p photoabsorption spectra of the FeCl2, FeBr2 and CoCl2 show a degree of similarity when compared to the corresponding spectra of the Fe and Co respectively. The comparison of the 3p photoelectron spectra of FeCl2, FeBr2 and CoCl2 with the corresponding 3p photoelectron spectra of the atomic Fe and Co respectively shows the more distinctive influence of the molecular binding on the valence electron. A further investigation of the influence of the molecular binding on the valence electron was made through the comparison of the 3p with 2p photoelectron data of the FeCl2

Fabrication and characterization of Manganese–Zinc Ferrite nanoparticles produced utilizing heat treatment technique

In this research, the thermal treatment technique has been employed to produce Mn0.5Zn0.5Fe2O4 nanoparticles. Manganese, Zinc and iron nitrates have been mixed with capping agent of polyvinylpyrrolidone. Several techniques have been used to examine the structural, morphological and optical properties of the prepared product. X-ray diffraction (XRD) has demonstrated the prepared product and showed that the product contains tetragonal crystalline structures. Scanning electron microscopy (SEM) has showed that the sample grain size is increasing alongside temperature calcination. Energy dispersive X-ray (EDX) has showed that the presence of Mn, Zn, Fe and O in the product nanoparticle was confirmed as original from the precursor starting materials. Transmission electron microscopy (TEM) images have demonstrated that elevating the different of calcination temperature from 500 °C to 650 °C has resulted in an increase average nanoparticle size from 12 nm to 19 nm. Fourier Transform Infrared Spectroscopy (FT-IR) has been used to describe compounds of the samples prepared before and after calcination

Calcined solution-based PVP influence on ZnO semiconductor nanopeprints properties

water-based solution of polyvinylpyrrolidone (PVP) at various concentrations and zinc nitrates were used in conjunction with calcination to produce zinc oxide semiconductor nanoparticles. The extent to which the zinc oxide semiconductor nanoparticles had become crystallized was measured using X-ray diffraction (XRD), whilst morphological characteristics were determined using scanning electron microscopy (SEM). Transmission electron microscopy (TEM) supported by XRD results were used to evaluate the average particle size. Fourier transform infrared spectroscopy (FT-IR) was then carried out in order to identify the composition phase, since this suggested that the samples contained metal oxide bands and that all organic compounds had been effectively removed after calcination. A UV-VIS spectrophotometer was used to determine the energy band gap and illustrate optical features. Additionally, photoluminescence (PL) spectra revealed that the intensity of photoluminescence decreased with a decrease in particle size. The obtained results have mainly been inclusive for uses by several semiconductor applications in different fields, such as environmental applications and studies, since an absorption process for energy wavelengths could efficiently occur

Defect seeded remote epitaxy of GaAs films on graphene.

Remote epitaxy is an emerging materials synthesis technique which employs a 2D interface layer, often graphene, to enable the epitaxial deposition of low defect single crystal films while restricting bonding between the growth layer and the underlying substrate. This allows for the subsequent release of the epitaxial film for integration with other systems and reuse of growth substrates. This approach is applicable to material systems with an ionic component to their bonding, making it notably appealing for III-V alloys, which are a technologically important family of materials. CVD growth of graphene and wet transfer to a III-V substrate with a polymer handle is a potentially scalable and low cost approach to producing the required growth surface for remote epitaxy of these materials, however, the presence of water promotes the formation of a III-V oxide layer, which degrades the quality of subsequently grown epitaxial films. This work demonstrates the use of an argon ion beam for the controlled introduction of defects in a monolayer graphene interface layer to enable the growth of a single crystal GaAs film by molecular beam epitaxy, despite the presence of a native oxide at the substrate/graphene interface. A hybrid mechanism of defect seeded lateral overgrowth with remote epitaxy contributing the coalescence of the film is indicated. The exfoliation of the GaAs films reveals the presence of defect seeded nucleation sites, highlighting the need to balance the benefits of defect seeding on crystal quality against the requirement for subsequent exfoliation of the film, for future large area development of this approach.EPSRC Graphene CDT Cambridge (EP/L016087/1) H2020 European Research Council (853365) Cambridge XPS System, part of Sir Henry Royce Institute - Cambridge Equipment, EPSRC grant EP/P024947/