Synthesis of Nanostructured Tin Oxide (SnO2) Powders and Thin Films Prepared by Sol-Gel Method

Nanocrystalline SnO2 powder was successfully prepared by using simple sol-gel technique. The sol-gel obtained was washed and calcinated at 400 C to obtain the SnO2 nano-powder. The structural property of (SnO2) nanocrystalline powder was investigated by using X-ray diffraction (XRD) technique. The optical properties were studied using Uv-Vis Spectroscopy, by recording the absorbance and transmittance spectra. The XRD pattern of the as-prepared sample demonstrated the formation of a rutile structure of SnO2 nanocrystallites. The Scanning Electron Microscopic (SEM) analysis showed a homogeneous distribution of quite small grains over scanned area. The Uv-Vis absorbance spectra also showed a characteristic peak of absorbance at 312 nm corresponding to SnO2. The energy band gap measurement for nanocrystalline SnO2 thin film was done from the graph of variation of (hν)2 versus hν. The measured value of optical bandgap energies for SnO2 thin film is 3.78 eV. The results show that the transmittance of the synthesized SnO2 film is 78 % in the spectral range 350 nm to 800 nm

Synthesis of Nanostructured Tin Oxide (SnO2) Powders and Thin Films Prepared by Sol-Gel Method

Nanocrystalline SnO2 powder was successfully prepared by using simple sol-gel technique. The sol-gel obtained was washed and calcinated at 400 C to obtain the SnO2 nano-powder. The structural property of (SnO2) nanocrystalline powder was investigated by using X-ray diffraction (XRD) technique. The optical properties were studied using Uv-Vis Spectroscopy, by recording the absorbance and transmittance spectra. The XRD pattern of the as-prepared sample demonstrated the formation of a rutile structure of SnO2 nanocrystallites. The Scanning Electron Microscopic (SEM) analysis showed a homogeneous distribution of quite small grains over scanned area. The Uv-Vis absorbance spectra also showed a characteristic peak of absorbance at 312 nm corresponding to SnO2. The energy band gap measurement for nanocrystalline SnO2 thin film was done from the graph of variation of (hν)2 versus hν. The measured value of optical bandgap energies for SnO2 thin film is 3.78 eV. The results show that the transmittance of the synthesized SnO2 film is 78 % in the spectral range 350 nm to 800 nm

Spray Deposited Nanocrystalline ZnO Transparent Electrodes: Role of Precursor Solvent

Nanocrystalline ZnO thin films were deposited by intermittent spray pyrolysis using different alcoholic and aqua-alcoholic precursor solvents. The XRD analysis reveals the polycrystallinity of hexagonal wurtzite type ZnO films with preferred c-axis orientation along [002] direction. The polycrystallinity increased due to use of aqua-alcoholic precursor solvent. The crystallite size was found to vary from 41.7 nm to 59.4 nm and blue shift in band-gap energy (3.225 eV to 3.255 eV) was observed due to aqua-alcoholic to alcoholic precursor solvent transition. The films deposited using alcoholic precursor solvent exhibited high transmittance (> 92 %) with low dark resistivity (10 – 3 Ω·cm) as compared to aqua-alcoholic precursor solvent. The effect of precursor solvent on resistivity, carrier concentration (η – /cm3), carrier mobility (μ – cm2V – 1s – 1), sheet resistance (Ω/) and figure of merit (ΦTC) is also reported. We recommend ethanol or methanol as a superior precursor solvent over aqua-alcoholic precursor solvent for deposition of device quality ZnO thin films

Large Scale Screening of Southern African Plant Extracts for the Green Synthesis of Gold Nanoparticles Using Microtitre-Plate Method

The preparation of gold nanoparticles (AuNPs) involves a variety of chemical and physical methods. These methods use toxic and environmentally harmful chemicals. Consequently, the synthesis of AuNPs using green chemistry has been under investigation to develop eco-friendly nanoparticles. One approach to achieve this is the use of plant-derived phytochemicals that are capable of reducing gold ions to produce AuNPs. The aim of this study was to implement a facile microtitre-plate method to screen a large number of aqueous plant extracts to determine the optimum concentration (OC) for the bio-synthesis of the AuNPs. Several AuNPs of different sizes and shapes were successfully synthesized and characterized from 17 South African plants. The characterization was done using Ultra Violet-Visible Spectroscopy, Dynamic Light Scattering, High Resolution Transmission Electron Microscopy and Energy-Dispersive X-ray Spectroscopy. We also studied the effects of temperature on the synthesis of the AuNPs and showed that changes in temperatures affect the size and dispersity of the generated AuNPs. We also evaluated the stability of the synthesized AuNPs and showed that some of them are stable in biological buffer solutions

Review on nanoparticles and nanostructured materials: History, sources, toxicity and regulations

Nanomaterials (NMs) have gained prominence in technological advancements due to their tunable physical, chemical and biological properties with enhanced performance over their bulk counterparts. NMs are categorized depending on their size, composition, shape, and origin. The ability to predict the unique properties of NMs increases the value of each classification. Due to increased growth of production of NMs and their industrial applications, issues relating to toxicity are inevitable. The aim of this review is to compare synthetic (engineered) and naturally occurring nanoparticles (NPs) and nanostructured materials (NSMs) to identify their nanoscale properties and to define the specific knowledge gaps related to the risk assessment of NPs and NSMs in the environment. The review presents an overview of the history and classifications of NMs and gives an overview of the various sources of NPs and NSMs, from natural to synthetic, and their toxic effects towards mammalian cells and tissue. Additionally, the types of toxic reactions associated with NPs and NSMs and the regulations implemented by different countries to reduce the associated risks are also discussed

Bottom-up microwave-assisted seed-mediated synthesis of gold nanoparticles onto nanocellulose to boost stability and high performance for SERS applications

The development of accurate, reliable, inexpensive and fully recyclable analytical platforms is of utmost relevance to several fields from medical diagnosis to environmental screening. Surface-enhanced Raman spectroscopy (SERS) is a compelling detection method with high specificity and sensitivity. In this work, a microwave-assisted synthesis method was used for fast and uniform in situ growth of gold nanoparticles (AuNPs) onto nanocellulose (NC) membranes, through a seedmediated process. The as-prepared membranes were fully optimized and its application as SERS platforms was demonstrated. A direct comparison with other cellulose-based substrates showed the superior characteristics of NC such as high mechanical strength, high surface area and lower porous content. An Enhancement Factor (EF) up to 106 was obtained using rhodamine 6G (R6G) 10-6 M as probe molecule and a remarkable shelf life of at least 7 months was achieved, with no special storage required. Preliminary results on the detection of label-free spike protein present in SARSCoV-2 virus are shown, through direct measurements on the optimized SERS membrane. We believe that this work evidences the effectiveness of in situ seed-mediated microwave-assisted synthesis as a fabrication method, the high stability of AuNPs and the superior characteristics of NC substrates to be used as SERS platforms.This work is funded by National Funds through FCT I.P., under the scope of the project UIDB/50025/2020-2023. The authors acknowledge the ERC AdG project DIGISMART ref. 787410 and EC project SYNERGY H2020-WIDESPREAD-2020-5, CSA, proposal n° 952169. Also, the authors thank funding co-financed by the Operational Programme for Competitiveness and Internationalisation (COMPETE 2020) and Lisbon Regional Operational Programme (Lisboa 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) under the projects ECO2COVID ref. 68174 and TecniCOV ref. 69745. A. C. Marques acknowledges funding from FCT I.P., through the PhD Grant SFRH/BD/115173/2016. The authors acknowledge Professor Pedro Costa from KAUST for the TEM imaging.info:eu-repo/semantics/publishedVersio

Inorganic-Organic Hybrid Nanomaterials for Therapeutic and Diagnostic Imaging Applications

Nanotechnology offers outstanding potential for future biomedical applications. In particular, due to their unique characteristics, hybrid nanomaterials have recently been investigated as promising platforms for imaging and therapeutic applications. This class of nanoparticles can not only retain valuable features of both inorganic and organic moieties, but also provides the ability to systematically modify the properties of the hybrid material through the combination of functional elements. Moreover, the conjugation of targeting moieties on the surface of these nanomaterials gives them specific targeted imaging and therapeutic properties. In this review, we summarize the recent reports in the synthesis of hybrid nanomaterials and their applications in biomedical areas. Their applications as imaging and therapeutic agents in vivo will be highlighted