Saif Ullah Awan

Bio: Saif Ullah Awan is an academic researcher from College of Electrical and Mechanical Engineering. The author has contributed to research in topics: Band gap & Materials science. The author has an hindex of 14, co-authored 45 publications receiving 692 citations. Previous affiliations of Saif Ullah Awan include Virginia Commonwealth University & COMSATS Institute of Information Technology.

Ferromagnetism in Li doped ZnO nanoparticles: The role of interstitial Li

Abstract: ZnO nanoparticles doped with Li (Zn1−yLiyO, y ≤ 0.1) have been investigated with emphasis on the correlation between their magnetic, electronic, and structural properties. In particular, defects such as interstitial Li and Zn atoms, substitutional Li atoms, and oxygen vacancies have been identified by X-ray photoelectron spectroscopy (XPS) and their respective roles in stabilization of the magnetic moment are discussed. X-ray diffraction (XRD) and XPS give clear evidence of Li presence at both substitutional and interstitial sites. XPS studies further show that the amount of substitutional Li defects (Lizn) and interstitial Li defects (Lii) vary non-monotonically with the Li concentration, with the Lii defects being noticeably high for the y = 0.02, 0.08, and 0.10 concentrations, in agreement with the XRD results. Magnetization studies show room temperature ferromagnetism in these nanoparticles with the moment being largest for the particles with high concentration of interstitial lithium and vice versa. Both interstitial Zn (Zni) defects and Zn-O bonds were determined from the Zn LMM Auger peaks; however, the variation of these with Li concentrations was not large. Oxygen vacancies (Vo) concentrations are estimated to be relatively constant over the entire Li concentration range. We relate the Lii and Zni defects to the formation and stabilization of Zn vacancies and thus stabilizing the p-type ferromagnetism predicted for cation (zinc) vacancy in the ZnO type oxides.

Fabrication of pure and moxifloxacin functionalized silver oxide nanoparticles for photocatalytic and antimicrobial activity.

Abstract: This paper reports the synthesis of silver oxide (Ag2O) and moxifloxacin functionalized silver oxide (M-Ag2O) nanoparticles for photocatalytic and antimicrobial activity. The Ag2O nanoparticles were synthesized by using 2 dimethyl amino ethanol as reducing agent. The BET surface area measured from N2 adsorption method was found to be 16.89 m2/g. The mix (cubic and hexagonal) phase of silver oxide (Ag2O) nanoparticles was confirmed by X-rays diffraction (XRD). The extra diffracted peaks were observed after moxifloxacin fictionalization. The scanning electron micrographs display spherical shaped particles of different sizes. The elemental composition and weight percent of both samples were studied by energy dispersive X-ray (EDX). The decrease in the weight percent of silver with the subsequent increase in the weight percent of carbon and oxygen revealed the successful loading of moxifloxacin onto Ag2O NPs. The two stages of weight loss due to the removal of physisorbed and chemisorbed water was examined during thermogravimetric analysis (TGA). The optical band gap derived from the diffuse reflectance spectrum (DRS) was 1.83 eV, which corresponds to the transmittance edge of 676 nm. The Fourier transform infrared (FTIR) band at 668.56 cm-1 confirms the successful synthesis of moxifloxacin functionalized silver oxide (Ag2O) nanoparticles. The pure Ag2O nanoparticles were used for the degradation of rhodamine 6G and 98.56% dye was degraded in 330 min. The bacterial species selected for the present study were Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans and Aspergillus Niger. Both pure and functionalized Ag2O NPs were screened against selected bacterial and fungal species and they showed improved activity with the volume of samples taken in wells. However, the activity of Ag2O NPs against fungi was found less effective than bacteria which may be due to the difference in the composition of the cell wall. Further gram-positive bacteria showed more resistance toward both samples as compared to the gram-negative bacteria. It was concluded that Ag2O NPs upon conjugation with moxifloxacin displayed promising antimicrobial activity.

Room-temperature ferromagnetism in graphite driven by two-dimensional networks of point defects

Abstract: Ferromagnetism usually only occurs in materials containing elements that form covalent 3d and 4f bonds. Its occurrence in pure carbon is therefore surprising, even controversial. A systematic magnetic force microscope study indicates that ferromagnetism in graphite is the result of localized spins that arise at grain boundaries.

Confinement of Ultrasmall Cu/ZnOx Nanoparticles in Metal–Organic Frameworks for Selective Methanol Synthesis from Catalytic Hydrogenation of CO2

Abstract: The interfaces of Cu/ZnO and Cu/ZrO2 play vital roles in the hydrogenation of CO2 to methanol by these composite catalysts. Surface structural reorganization and particle growth during catalysis deleteriously reduce these active interfaces, diminishing both catalytic activities and MeOH selectivities. Here we report the use of preassembled bpy and Zr6(μ3-O)4(μ3-OH)4 sites in UiO-bpy metal–organic frameworks (MOFs) to anchor ultrasmall Cu/ZnOx nanoparticles, thus preventing the agglomeration of Cu NPs and phase separation between Cu and ZnOx in MOF-cavity-confined Cu/ZnOx nanoparticles. The resultant Cu/ZnOx@MOF catalysts show very high activity with a space–time yield of up to 2.59 gMeOH kgCu–1 h–1, 100% selectivity for CO2 hydrogenation to methanol, and high stability over 100 h. These new types of strong metal–support interactions between metallic nanoparticles and organic chelates/metal-oxo clusters offer new opportunities in fine-tuning catalytic activities and selectivities of metal nanoparticles@MOFs.

Continuous Hydrothermal Synthesis of Inorganic Nanoparticles: Applications and Future Directions

Abstract: Nanomaterials are at the leading edge of the emerging field of nanotechnology. Their unique and tunable size-dependent properties (in the range 1–100 nm) make these materials indispensable in many modern technological applications. In this Review, we summarize the state-of-art in the manufacture and applications of inorganic nanoparticles made using continuous hydrothermal flow synthesis (CHFS) processes. First, we introduce ideal requirements of any flow process for nanoceramics production, outline different approaches to CHFS, and introduce the pertinent properties of supercritical water and issues around mixing in flow, to generate nanoparticles. This Review then gives comprehensive coverage of the current application space for CHFS-made nanomaterials including optical, healthcare, electronics (including sensors, information, and communication technologies), catalysis, devices (including energy harvesting/conversion/fuels), and energy storage applications. Thereafter, topics of precursor chemistry and ...