Journal of Nano Research Vol. 68

Abstract: Hollow graphitic porous carbon nanosphere (CNS) materials are synthesized from polymerization of resorcinol (R) and formaldehyde (F) in the presence of templating iron polymeric complex (IPC), followed by carbonization treatment. The effect of rapid heating in the carbonization process is investigated for the formation of hollow graphitic carbon nanospheres. The resulting CNS from rapid heating was characterized for its structure and properties by transmission electron microscope (TEM), x-ray diffraction (XRD), Raman spectroscopy, bulk conductivity measurement and Brunauer-Emmett-Teller (BET) surface area. Hollow graphitic CNS with reduced degree of agglomeration is observed under rapid heating during the carbonization process when compared to the CNS synthesized using the standard slow heating approach. Key words: carbon nanosphere (CNS), rapid pyrolytic carbonization, agglomeration

Abstract: In this research, MXene (Ti₃C₂) nanoflakes are implanted for the first time with Palm oil methyl ester (POME) to improve the nanofluids (POME/MXene) thermo-physical properties. The preparation, characterization, thermal and rheological properties was evaluated. POME/MXene nanofluid was induced with five different concentrations (0.01, 0.03, 0.05, 0.08, and 0.1 wt.%) of MXene to achieve the optimal properties that would be superior for a new heat transfer fluid. It is found that introducing more MXene nanoflakes into POME would expand the thermo-physical properties which will induce the rapid cooling of MXene based-nanofluids. Maximum enhancement of thermal conductivity for a MXene concentration and temperature of 0.1 wt.% and 65 ^oC respectively was measured to be ~ 176 % compared to the base fluid. Increasing amount of MXene did not effect the viscosity of the nanofluid. These results enable it to be utilized as a promising heat transfer fluid.

Abstract: Synthesis of nanoparticles of transition metals by using medicinal plants has been outstreched in recent years because of the characteristic features which are embodied in the end product. This work is proceded with the aim to synthesize and optimize copper nanoparticles (CuNPs-Pl) using aqueous extract of Polyalthia longifolia leaves (PlL) for characterization and evaluation of antimicrobial and antioxidant potential. The synthesis of CuNPs-Pl was confirmed by visual inspection of the dark brown residues in the reaction flask and via absorption band around 580nm by UV/Visible spectroscopy. Synthesis process was optimized through investigation of environmental variables. FTIR analysis was carried out for both PIL and CuNPs-Pl which identified the presence of alkanes, alcoholic, and aldehydic groups in the PlL and their encapsulation on the copper surface. The synthesized CuNPs-Pl were found to be spherical and rod shaped, and polydispersed when investigated through SEM study. Similarly, these nanoparticles had monoclinic structure and crystalline nature when analyzed by XRD. Moreover, these nanoparticles showed metallic form when EDX examination was done. Further, biological activities were performed. The synthesized nanoparticles showed considerable inhibition zones against Escherichia coli (12mm), Bacillus subtilis (11mm), Aspergillus niger (10mm), and Schyzophyllum commune (16mm) which depicted their powerful antibacterial and antifungal activity. Likewise, CuNPs-Pl were effeciently able to quench free radicals as indicated from the 2, 2-diphenyl-1-picrylhydrazyl (DPPH), hydrogen peroxide (H₂O₂), and nitric oxide (NO) assays by exhibiting 86.32, 50.45, and 48.23% inhibition respectively. Thus, the contemporary work has substantiated that low cost CuNPs-Pl can be highly proficient alternate or substitute of synthetic formulations.

Abstract: The effect of a magnetic source of variable strength has been studied on ferro-nanofluid incorporating nanoparticles of Cobalt ferrite (CoFe₂O₄) with water as a base fluid. Group method has been used to remodel the governing system to a system of ordinary differential equations. The recent study was motivated by inspecting the effect of four parameters including nanoparticles volume fraction, , Prandtl number, , magnetic field strength of the source,, and temperature difference ratio with respect to ambient temperature, . The results showed that the nanofluid velocity and shear stress increased as long as and increase. On the other hand, both are inversely related to the increment in Pr and Temperature distribution inside the boundary layer was noticed to increase due to the increment in Pr values and decrease due to the increment ratios. Contrarily, the heat flux throughout the boundary layer decreased and increased due to increasing respectively. Key words: Ferro-hydrodynamic; Nanofluids; Group Method

Abstract: The biogenesis of silver nanoparticles by microbes has become an essential branch in the field of nanotechnology because of its safe, environment-friendly, economical, and time-saving nature. In the current research work, we have screened some stress-tolerant bacteria based on pH, temperature, salt-tolerant efficacy and further utilized them for the synthesis of silver nanoparticles. The test bacterium was isolated from the soil sample through the serial dilution method on nutrient agar media (NAM). Based on identification using morphological characteristics, biochemical analysis, and 16srRNA sequencing bacteria were identified as Bacillus sp. The extracellular biosynthesis approach was used for synthesizing silver nanoparticles by Bacillus sp. Characterization of synthesized silver nanoparticles was done by using UV-Visible Spectrophotometer and absorbance peak was recorded at 430nm. Transmission electron microscopy (TEM) study of synthesized nanoparticles showed the shape of nanoparticles was spherical and hexagonal with a size ranging from 10nm-47nm. For the extracellular biosynthesis of silver nanoparticles pH was set to 7.0 and temperature at 37°C.

Abstract: Photochemistry to prepare platinum nanoparticles (Pt NPs) is an essential way to control Pt NPs catalyst size distribution. This article reports a series of morphologically controlled syntheses of Pt NPs loaded on modified carbon nanotube (Pt-CNTs). In the synthesis, Polyethylene glycol (PEG) participates in reactions both as a reducing agent and a stabilizer. Visible light irradiation was adopted as a kinetic controlling approach. Typical 4-nitrophenol (4-NP) reduction was adopted to probe the catalytic performances. Characterizations prove that visible light irradiation is an effective way to control the reaction process. In the optimized reaction conditions, i.e., when the ratio PEG:H₂O is 1:9, and the pH is 10, the as-prepared Pt NPs are consequently in a very narrow sized distribution with an average diameter of 1.29 nm. The Pt-CNTs present a high reaction rate constant of 0.624 min^-1 in the catalytic reduction of 4-NP. All the research results are beneficial for exploring more green chemistry and facile photochemical approaches in the controlled preparation of Pt nanocatalysts.

Abstract: In this study, the effect of reaction temperature on the properties of cobalt ferrite nanoparticles was investigated. X-ray diffraction analysis and Fourier transform infrared spectroscopy confirmed that synthesized nanoparticles are cobalt ferrite. Particle sizes and shapes were determined by a transmission electron microscope, and magnetic measurements were done using a vibrating sample magnetometer. The average particle size varies in the range of 5.7 - 10.7 nm as the temperature is raised from 30 to 80°C. With that, there is a transition from ferrimagnetic to superparamagnetic behaviors at 40°C. The critical size of cobalt ferrite nanoparticles for the superparamagnetic limit with zero coercivity is found to be around 6 nm, and its saturation magnetization value is 25.4 emu/g. This value is impressive higher compared to that in the other studies with similar preparation conditions.

Abstract: Indium gallium zinc oxide fin-field effect transistor (IGZO FinFET) characteristics are investigated and then compared with Zinc oxide fin-field effect transistor (ZnO FinFET) and the Silicon fin-field effect transistor (Si FinFET). This was done using 3D simulation. The threshold voltage for Si, ZnO, and IGZO is 0.75 V, 0.30 V and 0.05 V respectively. The silicon device has the highest transconductance (5.0 x 10^-7 S) and performs better than the other devices because it has less fixed charge defects. IGZO has the second-best value of Gm (3.6 x 10^-7 S), ZnO has the least value of Gm (3.4 x 10^-7 S). Si device has the least drain current (I_DS) value of 2.0 x 10^-7 A, ZnO device has a better I_DS value of 6.2 x 10^-6 A while IGZO device has the best I_DS value of 1.6 x 10^-5 A. IGZO is better than Si by two (2) order magnitude. The field effect mobility is 50.0 cm²/Vs for all three devices.

Abstract: Tin oxide nanoparticles (SnNPs) are very useful to be employed as an antibacterial agent for both gram-positive and gram-negative bacteria. In this present work, the synthesis of SnNPs was successfully carried out using the neodymium yttrium aluminum garnet (Nd:YAG) laser with a wavelength of 1064 nm, pulse duration of 7 ns, and a laser frequency of 10 Hz. Experimentally, a pulse Nd:YAG laser was directed and focused on a high-purity tin (Sn) metal, immersed in various liquid media including pure water and ethylene glycol. A brownish colloidal colour was produced both in pure water and ethylene glycol liquid media. Characterizations of tin oxide nanoparticles were made using UV-Vis, EDX, FTIR, and TEM. UV-Vis characterization produced absorbance values in pure water and ethylene glycol media of 1.314 a.u. and 1.119 a.u., respectively. TEM images show that the shape of tin oxide nanoparticles produced is spherical. Measurement of nanoparticle size distribution was made using image-J software and the average diameter of nano-size in the ethylene glycol medium is 12.55 nm, which is smaller than the size in the pure water of 19.98 nm. The EDX spectrum analysis results show that there are only Sn and O atoms in colloidal tin oxide nanoparticles (SnNPs). FTIR results show the formation of tin oxide (SnO₂) spectrum at the wavenumber of 629.03 cm^-1. The produced colloidal SnNPs were then applied as an antibacterial agent of E. coli using the disk diffusion method. Results certified that various concentrations of SnNPs of 10 ppm, 20 ppm, and 30 ppm gain the diameter of inhibition zone (DIZ) in sequence 6.50 mm, 6.75 mm, and 9.50 mm. Based on these experimental results, it shows that the higher the concentration of SnNPs given, the greater the ability to degrade and inhibit bacteria.

Abstract: In this research optical properties of synthesized gold-graphene/polyvinyl alcohol (AuG/PVA) nanocomposite have been investigated. Gold and graphene nano colloidal solution (NCS) synthesized by laser ablation method individually. The resulting NCS were characterized by UV-Vis absorption spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). PVA/Au and PVA/AuG with different concentration of AuG were mixed to form polymeric films via solution casting. Doped polymeric films were analyzed by FTIR and spectrophotometer analyses. The results show that by increasing of AuG concentration, the band gap energy of the PVA films significantly enhanced and other optical parameters such as refraction and extinction coefficients remarkably changed.