Current Nanoscience - Volume 21, Issue 5, 2025

This article presents structural and morphological analysis for graphene oxide (GO) synthesized via Hummers' method and for reduced Graphene Oxide (rGO) prepared by chemical reduction. Graphene Oxide is synthesized from graphite powder at room temperature. Hydrazine hydrate is used as a reducing agent to reduce the accumulated GO.

To understand the impact of reduction time on structural parameters of produced rGO, three different time limits, i.e. 4, 5, and 6 hrs at 800°C are used. FTIR spectra show the presence of all functional groups to confirm the authenticity of rGO samples. The XRD peaks are utilized to calculate different structural parameters for all the samples to identify the effect of reduction time. A change in the band gap energy may be noticed from UV-Vis absorption spectra.

It indicates that with the increase in reduction time, the absorption edge shifts to a lower wavelength value. FESEM micrographs reveal a flake-like random growth of rGO with prominent wrinkled structures, which is a signature of graphene-like 2D material.

Hence, from the structural and absorption studies, it can be concluded that an increase in reduction time will produce smaller rGO flakes in the Hummers synthesis method.

Titanium Dioxide (TiO2) is popular in the scientific community due to its wide variety of applications in optoelectronic devices, solar cells, gas sensors, photocatalytic reagents, and the biomedical industry. It is a wide band gap semiconductor with a band gap of 3.2eV. Usually, it shows three different phases, like anatase, rutile, and brookite, based on the synthesis method and annealing temperature.

Here, we report a simple chemical process to synthesize TiO2 nanostructures (NSs) at low temperatures to study the impact of growth time on structural and morphological properties. During synthesis, we permitted the samples to grow for 5 hr (sample-T5) and 7 hr (sample-T7) and continued the stirring process accordingly. We performed XRD, UV-Vis, and FESEM analysis with the samples.

XRD confirmed the effect of growth time on the size of the structures, and a shift in the absorption edge was observed in UV-Vis spectra, which indicated a change in the band gap. FESEM confirmed the change in nanostructures’ size in both samples.

The tuning in band gap due to growth time variation may be an interesting phenomenon to explore for modern scientific applications.

Recently, there has been a lot of interest in environmentally friendly nanoparticle synthesis. Silver nanoparticles (AgNPs) are promising against antibiotic resistance due to their high surface energy, robust action, and excellent adsorbability.

The primary objective of this study was to assess the antibacterial efficacy of AgNPs that were manufactured using three environmentally friendly methods (lemon, Streptomyces, and chitosan). Furthermore, the study attempted to investigate the potential toxicity of these nanoparticles on mice.

The synthesis of AgNPs was characterized by XRD, TEM FTIR, and TGA. The antimicrobial effect of AgNPs was studied using the disc diffusion method and minimum inhibitory concentration (MIC). The antibacterial mechanism of AgNPs was determined using different methods, such as released glucose and proteins, respiratory chain inhibition, plasma membrane fluorescence anisotropy, DNA fragmentation, gel electrophoresis, and cell membrane potential.

The TEM analysis of Ag NPs showed predominantly spherical particles with a size distribution of 10-60 nm. AgNPs synthesized by the three green methods showed antibacterial and fungal activity. The antibacterial mechanisms of AgNPs involved inhibition of LDH activity, increased protein and glucose leakage, DNA and protein damage, and depolarization and destabilization of the plasma membrane. AgNPs, on the other hand, increased alanine aminotransferase, aspartate aminotransferase, urea, creatinine, malondialdehyde, and nitric oxide levels in mice while decreasing glutathione reduced.

Our study showed that AgNPs synthesized by Streptomyces, lemon, and chitosan have powerful antimicrobial properties. Chitosan-AgNPs showed the most pronounced antibacterial action, although it displayed significant toxicity in mice. Conversely, lemon-AgNPs revealed the least notable impact.

Orthodontic arch wires, typically made of Nickel Titanium (NiTi), are widely utilized in dental procedures for correcting teeth misalignment and jaw issues due to their favorable mechanical attributes and cost-effectiveness. However, these NiTi wires are prone to corrosion in the oral environment, leading to diminished mechanical stability, compromised aesthetics, and potential health concerns for patients.

There is a growing demand to augment the corrosion resistance and stability of orthodontic wires. Hence, this study aimed to address these issues. Herein, zirconium dioxide (ZrO2) and oxidized ethylene glycol (OEG) films were deposited onto NiTi wires to improve the corrosion resistance and stability.

NiTi wires were modified by a two-step process involving electrodeposition of ZrO2 and oxidized ethylene glycol (OEG) film. The surface characterizations of coated material (OEG/ZrO2/NiTi) were carried out by using Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Electron Microprobe Analysis (E-Map) to confirm the elemental composition of the coated NiTi wire.

The OEG/ZrO2/NiTi wire exhibited a potentiodynamic polarization resistance of 547037 Ω and higher stability than the bare NiTi wire (396421 Ω). The corrosion rate for OEG/ZrO2/NiTi wire was found to be 0.040 mm/year, which was comparatively lower than a bare NiTi wire (0.069 mm/year). Due to the formation of OEG/ZrO2 film, NiTi wire became electrically insulative and showed a higher impedance than bare NiTi wire.

The bilayer coating of ZrO2 and OEG has proven to significantly improve the corrosion resistance and stability of the wires. Thus, these materials can be considered for coating orthodontic arch wires with improved corrosion stability.

Orthodontic treatment relies on stainless steel (SS) wires to apply forces and torque to reposition teeth. However, SS wires are susceptible to wear and corrosion in the oral environment, necessitating improvements in their durability.

This study explores the potential of a coating comprising titanium dioxide (TiO2) and polyhexamethylene biguanide (PHMB) to enhance the corrosion resistance of SS wires.

SS wires were coated with a solution containing PHMB and TiO2 using a drop-casting technique. Field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDAX), and electrochemical tests, including impedance spectroscopy and potentiodynamic polarization, were conducted to characterize the coated wires and evaluate their corrosion resistance.

FE-SEM, EDAX, and Emap analysis confirmed the presence and uniform deposition of PHMB/TiO2 onto the SS wire surface. Electrochemical tests revealed that the PHMB/TiO2-coated SS wires exhibited a significantly lower corrosion rate (7.08×10⁻⁶ mm/year) and higher corrosion resistance (562466 Ω) compared to bare SS.

The PHMB/TiO2 coated SS wire exhibited high corrosion resistance and offered potential benefits for orthodontic treatments. Further research and optimization of this coating may help to improve the durability and reliability of orthodontic appliances.

A novel attempt to degrade alizarine yellow R (AYR) by lead dioxide (PbO2)/ neodymium (Nd) coated Ti anode was investigated.

Ti/Zr-SnO2/PbO2-Nd electrode showed high oxygen evolution potential, high current density, and neutral conditions, which favored the degradation of AYR. The PbO2-Nd layer on Ti/Zr-SnO2 was further characterized by scanning electron microscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy. The electrochemical properties of Ti/Zr-SnO2/PbO2-Nd electrode were evaluated by cyclic voltammetry, AC impedance spectroscopy, and accelerated life test.

The relatively higher oxygen evolution overpotential (~1.80 V) of the developed electrode can effectively suppress the occurrence of surface side reactions and oxygen evolution. A relatively lower charge transfer resistance (Rct, 18.0 Ω) of Ti/Zr-SnO2/PbO2-Nd electrode could be found. The Ti/Zr-SnO2/PbO2-Nd electrode exhibited an accelerated lifetime of 110 min under a very high current density of 10,000 A/m². The doping of Nd could produce loosely-stacked sheet-like structures, thus, the number of active sites on the electrode surface increases.

Moreover, an outstanding conductivity of Ti/Zr-SnO2/PbO2-Nd electrode was obtained, which favored the electron transfer and catalytic activity of the modified electrode. The Ti/Zr-SnO2/PbO2-Nd electrode exhibited improved electrochemical performances and higher oxygen evolution potential, and the highest oxygen evolution potential is 1.80 V. Under the current density of 30 mA/cm², the electrocatalytic degradation efficiency of 92.3% could be achieved in 180 min. The electrochemical oxidation of AYR at the Ti/Zr-SnO2/PbO2-Nd electrode proved to be feasible and effective, indicating that it might be used for the elimination of AYR from wastewater.