Sharif Digital Repository

Graphene nanoribbons (GNRs) fabricated using electron beam lithography are investigated using tip-enhanced Raman spectroscopy (TERS) with a spatial resolution of 5 nm under ambient conditions. High-resolution TERS imaging reveals a structurally modified 5-10 nm strip of disordered graphene at the edge of the GNRs. Furthermore, hyperspectral TERS imaging discovers the presence of nanoscale organic contaminants on the GNRs. These results pave the way for nanoscale chemical and structural characterisation of graphene-based devices using TERS. © The Royal Society of Chemistry 2021  

A new plasmonic Ag hybridized CuWO4/WO3 heterostructure was successfully synthesized via a ligand-assisted sol gel method. The as-prepared plasmonic nanohybrid was thoroughly characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy, photoluminescence (PL) spectrometry, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis and electrochemical impedance spectroscopy (EIS). Moreover, the photocatalytic activity was evaluated by photo-degradation of methylene blue (MB) under visible light irradiation. The results indicate that the as-prepared plasmonic Ag-CuWO4/WO3 nanohybrid (compared to pure... 

Bacterial toxicity of graphene nanosheets in the form of graphene nanowalls deposited on stainless steel substrates was investigated for both Gram-positive and Gram-negative models of bacteria. The graphene oxide nanowalls were obtained by electrophoretic deposition of Mg2+-graphene oxide nanosheets synthesized by a chemical exfoliation method. On the basis of measuring the efflux of cytoplasmic materials of the bacteria, it was found that the cell membrane damage of the bacteria caused by direct contact of the bacteria with the extremely sharp edges of the nanowalls was the effective mechanism in the bacterial inactivation. In this regard, the Gram-negative Escherichia coli bacteria with an... 

Growing demands for clean and renewable energy technologies have sparked broad research on the development of highly efficient and stable non-noble metal electrocatalysts for oxygen evolution reaction (OER). In this regard, in the present work a three-dimensional Fe2TiO5/nitrogen-doped graphene (denoted as 3D FTO/NG) hybrid electrocatalyst was synthesized via a facile in-situ process using a hydrothermal method. Structural characterization of the prepared nanocomposite is performed by various techniques e.g. field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) analysis, Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy spectra (XPS),... 

Electrospinning of composite polymer solutions provides fantastic potential to prepare novel nanofibers for use in a variety of applications. The addition of graphene (G) and graphene oxide (GO) nanosheets to bioactive polymers was found to enhance their conductivity and biocompatibility. Composite conductive nanofibers of polyaniline (PANI) and polyacrylonitrile (PAN) with G and GO nanosheets were prepared by an electrospinning process. The fabricated membranes were investigated by physical and chemical examinations including scanning electron microscopy (SEM), Raman spectroscopy, x-ray diffraction (XRD) and tensile assay. The muscle satellite cells enriched by a pre-plating technique were... 

The creation of novel engineered multimodal nanoparticles (NPs) is a key focus in bionanotechnology and can lead to deep understanding of biological processes at the molecular level. Here, we present a multi-component system made of gold-coupled core-shell SPIONs, as a new nanoprobe with signal enhancement in surface Raman spectroscopy, due to its jagged-shaped gold shell coating  

Nanoparticles for biomedical use must be cytocompatible with the biological environment that they are exposed to. Current research has focused on the surface functionalization of nanoparticles by using proteins, polymers, thiols and other organic compounds. Here we show that inorganic nanoparticles such as titanium oxide can be coated by pyrolytic carbon (PyC) and that the coating has cytocompatible properties. Pyrolization and condensation of methane formed a thin layer of pyrolytic carbon on the titanium oxide core. The formation of the PyC shell retards coalescence and sintering of the ceramic phase. Our MTT assay shows that the PyC-coated particles are cytocompatible at employed doses  

The significant role of protein nanoparticle interactions in nanomedicine and nanotoxicity is emerging recently through the identification of the nanoparticles (NP) protein (biomolecule) corona. The dynamic layer of proteins and/or other biomolecules adsorbed to the nanoparticle surface determines how a NP interacts with living systems and thereby modifies the cellular responses to the NP. Ehrenberg and co-workers used cultured endothelium cells as a model for vascular transport of polystyrene NP with various functional groups, which showed that the capacity of the various NP surfaces to adsorb proteins was indicative of their tendency to associate with cells. The quantification of the... 

Molybdenum disulfide (MoS2), a two-dimensional transition metal has a 2D layered structure and has recently attracted attention due to its novel catalytic properties. In this study, MoS2 has been successfully intercalated using chemical and physical intercalation techniques, while enhancing its surface properties. The final intercalated MoS2 is of many interests because of its low-dimensional and potential properties in in-situ catalysis. In this research, we report different methods to intercalate the layers of MoS2 successfully using acid-treatment, ultrasonication, oxidation and thermal shocking. The other goal of this study is to form S[dbnd]O bonds mainly because of expected enhanced... 

Green tea-reduced graphene oxide (GT-rGO) sheets have been exploited for high efficiency near infrared (NIR) photothermal therapy of HT29 and SW48 colon cancer cells. The biocompatibility of GT-rGO sheets was investigated by means of MTT assays. The polyphenol constituents of GT-rGO act as effective targeting ligands for the attachment of rGO to the surface of cancer cells, as confirmed by the cell granularity test in flow cytometry assays and also by scanning electron microscopy. The photo-thermal destruction of higher metastatic cancer cells (SW48) is found to be more than 20% higher than that of the lower metastatic one (HT29). The photo-destruction efficiency factor of the GT-rGO is... 

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the COVID-19 pandemic that has been spreading around the world since December 2019. More than 10 million affected cases and more than half a million deaths have been reported so far, while no vaccine is yet available as a treatment. Considering the global healthcare urgency, several techniques, including whole genome sequencing and computed tomography imaging have been employed for diagnosing infected people. Considerable efforts are also directed at detecting and preventing different modes of community transmission. Among them is the rapid detection of virus presence on different surfaces with which people may come in... 

Recently, hybrid graphene–quantum dot systems have attracted increasing attention for the next-generation optoelectronic devices such as ultrafast photo-detectors and solar energy harvesting. In this paper, a novel, one-step, reproducible, and solution-processed method is introduced to prepare hybrid graphene–PbS colloids by employing supercritical ethanol. In the hybrid nanocomposite, PbS quantum dots (~3 nm) are decorated on the reduced graphene oxide (rGO) nanosheets (~1 nm thickness and less than 1 micron lengths). By employing X-ray photoelectron and Raman and infrared spectroscopy techniques, it is shown that the rGO nanosheets are bonded to PbS nanocrystals through carboxylic bonds.... 

Nanotechnology has illustrated significant potentials in biomolecular-sensing applications; particularly its introduction to anti-doping detection is of great importance. Illicit recreational drugs, substances that can be potentially abused, and drugs with dosage limitations according to the prohibited lists announced by the World Antidoping Agency (WADA) are becoming of increasing interest to forensic chemists. In this review, the theoretical principles of optical biosensors based on noble metal nanoparticles, and the transduction mechanism of commonly-applied plasmonic biosensors are covered. We review different classes of recently-developed plasmonic biosensors for analytic determination... 

It is estimated that 20% of couples are infertile, and half of these infertility cases are linked to men. One of conditions that can affect male fertility is asthenozoospermia. We applied Raman spectroscopy to the analysis of the metabolome of the human seminal plasma, and used chemometrics on the patterns of Raman spectra obtained. Significant changes were observed in the metabolome of the human seminal plasma of asthenozoospermic patients  

In this work, two important opioid antagonists, naltrexone and oxycodone, were prepared from thebaine and were characterized by IR, 1H NMR and 13C NMR spectroscopy. Moreover, computational NMR and IR parameters were obtained using density functional theory (DFT) at B3LYP/6-311++G* * level of theory. Complete NMR and vibrational assignment were carried out using the observed and calculated spectra. The IR frequencies and NMR chemical shifts, determined experimentally, were compared with those obtained theoretically from DFT calculations, showed good agreements. The RMS errors observed between experimental and calculated data for the IR absorptions are 85 and 105 cm-1, for the 1H NMR peaks are... 

Due to its high discharge capacity, low cost, and good safety, LiNi0.5Co0.2Mn0.3O2 (NCM 523) is regarded as a promising cathode material for the next-generation of lithium-ion batteries. However, poor cycling stability and rate capability are the main disadvantages of the NCM 523 cathode material. In this work, SiO2 single layer-coated and reduced graphene oxide (outer)/SiO2 (inner) double layer-coated NCM 523 have been prepared by a facile wet chemical method. Field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy results confirm that NCM 523... 

Viral diseases have long been among the biggest challenges for healthcare systems around the world. The recent Coronavirus Disease 2019 (COVID-19) pandemic is an example of how complicated the situation can get if we are not prepared to combat a viral outbreak in time, which brings up the need for quick and affordable biosensing platforms and vast knowledge of potential antiviral effects and drug/gene delivery opportunities. The same challenges have also existed for nonviral immunogenic disorders. Nanomedicine is considered a novel candidate for effectively overcoming these worldwide challenges. Among the versatile nanomaterials commonly used in biomedical applications, graphene has recently... 

In the present study, a novel α-MnO2/AgI photocatalyst was successfully fabricated by using hydrothermal/precipitation methods, and its photocatalytic performance was evaluated from the degradation of Acid blue 92 (AB92) dye under visible light irradiation. The surface and crystalline structure, morphology, and electro-chemical properties of the as-made photocatalyst were investigated by BET, XRD, XPS, SEM-EDS, TEM, DRS, PL, PC, and Raman analysis. The optimized nanocomposite (α-MnO2/AgI) with a weight ratio of 1:15 showed the best photocatalytic activity in the decomposition of AB92 with a removal efficiency of 100% in 40 min which was better than that of pure α-MnO2 (48%) and AgI (61%),... 

The treatment of water contaminated by bacteria is becoming a necessity. The nanomaterials possessing both intrinsic antibacterial properties and photocatalytic activity are excellent candidates for water disinfection. The powdered form of nanomaterials can be aggregated while embedding the nanomaterials into the NFs can overcome the limitation and enhance the photocatalytic activity and transition from UV-light to visiblelight. Here, graphene oxide (GO) was synthesized, grafted to chitosan, and decorated with silver nanoparticles (Ag NPs) to produce Ag-decorated reduced GO-graft-Chitosan (AGC) NPs. The blends of polyacrylonitrile (PAN) and AGC NPs were prepared in various concentrations of... 

Resonance Raman spectroscopy has long been established as one of the most sensitive techniques for detection, structure characterization, and probing the excited-state dynamics of biochemical systems. However, the analysis of resonance Raman spectra is much facilitated when measurements are accompanied by Density Functional Theory (DFT) calculations that are expensive for large biomolecules. In this work, resonance Raman spectra are therefore computed with the Density Functional Tight-Binding (DFTB) method in the time-dependent excited-state gradient approximation. To test the accuracy of the tight-binding approximations, this method is first applied to typical resonance Raman benchmark...