- Award ID(s):
- 2112595
- NSF-PAR ID:
- 10422764
- Date Published:
- Journal Name:
- Materials Express
- Volume:
- 12
- Issue:
- 9
- ISSN:
- 2158-5849
- Page Range / eLocation ID:
- 1211 to 1215
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Bimagnetic nanoparticles show promise for applications in energy efficient magnetic storage media and magnetic device applications. The magnetic properties, including the exchange bias of nanostructured materials can be tuned by variation of the size, composition, and morphology of the core vs overlayer of the nanoparticles (NPs). The purpose of this study is to investigate the optimal synthesis routes, structure and magnetic properties of novel CoO/NiFe 2 O 4 heterostructured nanocrystals (HNCs). In this work, we aim to examine how the size impacts the exchange bias, coercivity and other magnetic properties of the CoO/NiFe 2 O 4 HNCs. The nanoparticles with sizes ranging from 10 nm to 24 nm were formed by synthesis of an antiferromagnetic (AFM) CoO core and deposition of a ferrimagnetic (FiM) NiFe 2 O 4 overlayer. A highly crystalline magnetic phase is more likely to occur when the morphology of the core-overgrowth is present, which enhances the coupling at the AFM-FiM interface. The CoO core NPs are prepared using thermal decomposition of Co(OH) 2 at 600 °C for 2 hours in a pure argon atmosphere, whereas the HNCs are obtained first using thermal evaporation followed by hydrothermal synthesis. The structural and morphological characterization made using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and scanning electron microscopy (SEM) techniques verifies that the HNCs are comprised of a CoO core and a NiFe 2 O 4 overgrowth phase. Rietveld refinement of the XRD data shows that the CoO core has the rocksalt (Fd3 m) crystal structure and the NiFe 2 O 4 overgrowth has the spinel (C12/m1) crystal structure. SEM-EDS data indicates the presence and uniform distribution of Co, Ni and Fe in the HNCs. The results from PPMS magnetization measurements of the CoO/NiFe 2 O 4 HNCs are discussed herein.more » « less
-
Mubarak, Nabisab M. ; Walvekar, Rashmi ; Arshid, Numan ; and Khalid, Mohammad (Ed.)Metal oxides are useful for the detection and sensing of combustible and toxic gases, and for use in lithium batteries and solar cells. The present study focuses on the spectroscopic investigation of commercial and in-house laboratory synthesized tetragonal tin dioxide (SnO2), aimed at studying its physical and chemical properties at nanoscale levels and in bulk. We have investigated the pure powder form and thin films prepared on two different types of substrate, silicon and UV-Quartz, each with five different thicknesses (i.e. 41, 78, 96.5, 373, and 908 nm). Raman spectroscopy with two different laser excitation wavelengths, namely 780 and 532 nm, has been used to investigate the various SnO2 vibrational modes. Thermal effects on the primary vibrational features in the Raman spectra have been studied in the range 30–170 °C. X-ray diffraction (XRD) spectra have been recorded to confirm the rutile structure of tin dioxide and to obtain information on the spherical grain particle size of SnO2 with EDS analysis for the thin film samples. Scanning Electron Microscope (SEM) images have been recorded in order to understand the morphology of the particles of SnO2 at the nanoscale level. In addition, FT-IR spectra have been obtained to study the IR-active vibrational modes for the bulk and thin film samples on the two substrates. Moreover, UV-VIS spectra have been employed to determine the energy band gap for the SnO2 film samples by an efficient process facilitated by a Tauc plot technique utilizing an in-house developed python script.more » « less
-
This article belongs to the Special Issue Synthesis and Applications of Gold Nanoparticles) Rodolphe Antoine (Ed.)
This research focuses on the plant-mediated green synthesis process to produce gold nanoparticles (Au NPs) using upland cress (Barbarea verna), as various biomolecules within the upland cress act as both reducing and capping agents. The synthesized gold nanoparticles were thoroughly characterized using UV-vis spectroscopy, surface charge (zeta potential) analysis, scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray diffraction (XRD). The results indicated the synthesized Au NPs are spherical and well-dispersed with an average diameter ~11 nm and a characteristic absorbance peak at ~529 nm. EDX results showed an 11.13% gold content. Colloidal Au NP stability was confirmed with a zeta potential (ζ) value of −36.8 mV. X-ray diffraction analysis verified the production of crystalline face-centered cubic gold. Moreover, the antimicrobial activity of the Au NPs was evaluated using Gram-negative Escherichiacoli and Gram-positive Bacillus megaterium. Results demonstrated concentration-dependent antimicrobial properties. Lastly, applications of the Au NPs in catalysis and biomedicine were evaluated. The catalytic activity of Au NPs was demonstrated through the conversion of 4-nitrophenol to 4-aminophenol which followed first-order kinetics. Cellular uptake and cytotoxicity were evaluated using both BMSCs (stem) and HeLa (cancer) cells and the results were cell type dependent. The synthesized Au NPs show great potential for various applications such as catalysis, pharmaceutics, and biomedicine.
-
Astounding graphitic carbon nitride (g-C 3 N 4 ) nanostructures have attracted huge attention due to their unique electronic structures, suitable band gap, and thermal and chemical stability, and are insinuating as a promising candidate for photocatalytic and energy harvesting applications. The growth of a free-standing film is desirable for widespread electronic devices and electrochemical applications. Here, we present a facile approach to prepare free-standing films (15 mm × 10 mm × 0.5 mm) comprising g-C 3 N 4 nanolayers by the pyrolysis of dicyandiamide (C 2 H 4 N 4 ) utilizing the chemical vapor deposition (CVD) technique. The synthesis is done under low-pressure conditions of argon (∼3 Torr) and at a temperature of 600 °C. The as-synthesized g-C 3 N 4 films are systematically studied for their structural/microstructural characterization using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR) and UV-visible spectroscopy techniques. The excitation-dependent photoluminescence (PL) spectra of the as-synthesized g-C 3 N 4 film exhibited an intense, stable and broad emission peak in the visible region at ∼459 nm. The emission spectra of free-standing g-C 3 N 4 films show a blue shift and band sharpening compared to that of the g-C 3 N 4 powder.more » « less
-
In this study, fabrication processes of solid electrolyte/cathode interfaces for their use in next‐generation all‐solid‐state lithium‐ion battery (LIB) applications are described. Standard lithium
– aluminum– titanium– phosphate (LATP) solid electrolyte and lithium– manganese oxide (LMO) spinel cathode ceramic half cells are assembled using two all‐solid‐state methods: a) co‐sintering the cathode and electrolyte materials via field‐assisted sintering and b) field‐assisted high‐temperature bonding. The morphology and composition of the interfaces are analyzed by scanning electron microscopy (SEM) and energy‐dispersive X‐ray spectroscopy (EDS). This study reveals that the formation of interphases can be significantly decreased by separately performing the densification and joining procedures. Electrochemical impedance spectroscopy (EIS) is applied to understand and determine the effect of the manufactured interfaces on the system conductivity. Based on the results, it is concluded that the high‐temperature bonding technique appears to be a suitable technique for future production of all‐solid‐state LIBs.