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Laser Irradiation of Metal Oxide Films and Nanostructures: Applications and Advances
No full textRecent technological advances in developing a diverse range of lasers have opened new avenues in material processing. Laser processing of materials involves their exposure to rapid and localized energy, which creates conditions of electronic and thermodynamic nonequilibrium. The laser-induced heat can be localized in space and time, enabling excellent control over the manipulation of materials. Metal oxides are of significant interest for applications ranging from microelectronics to medicine. Numerous studies have investigated the synthesis, manipulation, and patterning of metal oxide films and nanostructures. Besides providing a brief overview on the principles governing the laser-material interactions, here, the ongoing efforts in laser irradiation of metal oxide films and nanostructures for a variety of applications are reviewed. Latest advances in laser-assisted processing of metal oxides are summarized
Highly efficient fluorescence quenching with chemically exfoliated reduced graphene oxide
Get PDFFluorescence quenching is a valuable tool to study many macromolecular assemblies. It is well-known that graphitic systems such as the reduced graphene oxide (rGO) can strongly quench the emission of dye molecules through energy transfer. In this work, the authors demonstrate comparative study of fluorescence quenching between different graphitic system such as rGO, graphene oxide (GO), and graphite, which is not reported so far. As compared to graphite and GO sheets, rGO shows more quenching capability because of more surface area and efficient p-p stacking. The fluorescence quenching has been performed using Rhodamine B dye. The scanning electron microscopic micrographs revealed that Rhodamine B dye is uniformly absorbed on rGO. The fluorescence quenching has been done with the fixed concentration of Rhodamine organic dye with all three forms of carbon. The spectroscopic results exhibit that the chemically exfoliated rGO was almost 16 times better than graphite and GO. The obtained results suggest that rGO can be used for better quenching capability in biosensing applications
Cytotoxicity of Graphene Oxide (GO) and Graphene Oxide Conjugated Losartan Potassium (GO-LP) on Neuroblastoma (NB41A3) Cells
No full textDespite several advancements in the biomedical sciences, an efficient cancer therapy still remains a challenge. Nanomedicines have shown potential to overcome certain roadblocks faced in the existing treatment modalities. Losartan potassium (LP) which is a known vasodilator also exhibits anti fibrolytic and anti-metastatic properties altogether. Further, also being a potential angiotensin II type 1 receptor antagonist, it has been well explored for down regulating tumourogenic biomarkerslike VEGF-A (Vascular endothelial growth factor A) and suppression of neovascularization, making it a suitable drug to target for cancer treatment. Besides this, it too reflected the stimulation of pro apoptotic signaling pathways. But due to its lower bioavailability and extensive hepatic metabolism its therapeutic index reduces down. Thus, the present study is focused on designing a nano-delivery system using graphene oxide (GO) as a nano-vehicle and conjugated the LP with it. Then, the successful synthesis of GO and GO-LP nano conjugates were characterized by high-resolution transmission electron microscopy, X-ray diffraction, FTIR and UV visible spectroscopy, confirming the formation of nanosheets. The qualitative morphological evaluation of NB41A3 neuroblastoma cell line treated with bare GO, LP and GO-LP using microscopy and DAPI staining revealed the inhibitory action of GO-LP nano conjugate on cell proliferation. Additionally, the cytotoxicity was also estimated using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide), Nitric oxide (NO) and Lactate dehydrogenase (LDH) assays. The results show that GO-LP significantly suppresses the cell viability in comparison to control and bare GO suggesting that the designed system may express its potential to be used with existing chemo drugs for the treatment of neural cancers
Competition between electron pairing and phase coherence in superconducting
Get PDFIn LaAlO3/SrTiO3 heterostructures, a gate tunable superconducting electron gas is confined in a quantum well at the interface between two insulating oxides. Remarkably, the gas coexists with both magnetism and strong Rashba spin-orbit coupling. However, both the origin of superconductivity and the nature of the transition to the normal state over the whole doping range remain elusive. Here we use resonant microwave transport to extract the superfluid stiffness and the superconducting gap energy of the LaAlO3/SrTiO3 interface as a function of carrier density. We show that the superconducting phase diagram of this system is controlled by the competition between electron pairing and phase coherence. The analysis of the superfluid density reveals that only a very small fraction of the electrons condenses into the superconducting state. We propose that this corresponds to the weak filling of high-energy d(xz)/d(yz) bands in the quantum well, more apt to host superconductivity
GaN-UV photodetector integrated with asymmetric metal semiconductor metal structure for enhanced responsivity
No full textFabrication of very thin GaN ultraviolet photodetectors on Si (111) substrate integrated with asymmetric (Pt-Ag, Pt-Cr) metal-semiconductor-metal (MSM) structure have been illustrated. Designed GaN photodetection device displays significant enhancement in responsivity for asymmetric (Pt-Ag) MSM structure (280 mA/W) in comparison to symmetric (Pt-Pt) MSM structure (126 mA/W) at 10 V bias. The fabricated asymmetric and symmetric devices also exhibit fast response time in the range of 30-59 ms. The enhancement in responsivity using asymmetric MSM structure ascribed to large difference in work function which lead to change in Schottky barrier height of the metal semiconductor junction. Additionally, power dependent photoresponse analysis of GaN asymmetric (Pt-Ag) ultraviolet photodetector was showing a responsivity of 116 mA/W at low optical power of 1 mW. Such GaN asymmetric MSM ultraviolet photodetectors having high responsivity can extensively be used for low power, high speed ultraviolet photo detection application
Design of a Stable DC Voltage Source and Computer Controlling of It Using an Indigenously Developed All-Digital Addressing-Cum-Control Hardware
No full textWe have developed a digitally operated addressing and control module (DACM) for addressing and controlling of equipment from a remote computer using a communication protocol developed in-house. This is useful for automation of an experiment that uses multiple equipment in a pre-decided synchronized manner. We also report design of a multipurpose high voltage direct current (DC) source that provides output of 0-100 V with an average stability of 1.90 (36) mV and has minimum step size of 3 mV. Operation of the DACM is examined by selecting the desired equipment, which in this case is the dc source, and remotely controlling its output from a computer. We also show that this can generate voltage with different waveforms within a 0-10 Hz frequency bandwidth. Such computer controlled ultra-stable high voltage sources tuneable to any arbitrary waveforms at low frequencies have many applications such as, driving a piezo for smooth scanning of laser frequencies, tuning length of a Fabry-Perot cavity, biasing of the electrodes in an ion trap and so on
Analysis of Extended Threshold Wavelength Photoresponse in Nonsymmetrical p-GaAs/AlGaAs Heterostructure Photodetectors
No full textWe analyze the extended threshold wavelength photoresponse beyond the standard threshold limit (lambda(t) = 1.24/Delta, where Delta is the activation energy) in nonsymmetrical p-GaAs/AlGaAs heterostructure photodetectors with a barrier energy offset. We propose that hot-cold hole carrier interactions in the p-GaAs absorber are responsible for the threshold wavelength extension. Experimental results are analyzed by considering a quasi-Fermi distribution of hot holes at a hot hole temperature (T-H), which is much higher than the lattice temperature (T-L). The experimental photoresponse is fitted using an escape cone model, modified with a quasi-Fermi level (E-quasiF). The simulated results are found to be in good agreement with experimental data, justifying the model used
A fluorene-core-based electron acceptor for fullerene-free BHJ organic solar cells-towards power conversion efficiencies over 10%
No full textA small molecule non-fullerene electron acceptor (SMNFEA), bearing a furan pi-spacer and dicyano-n-hexyl rhodanine as flanking groups, was designed and synthesized for organic solar cell applications. Organic photovoltaic devices based on FRdCN(2) and PTB7-Th polymer donors exhibited a highly improved efficient power conversion efficiency of 10.7%, which is the highest so far for OSCs fabricated from fluorene-core-based SMNFEA
Tuning the thermoelectric properties by manipulating copper in Cu2SnSe3 system
No full textCu2+xSnSe3 (0 <= x <= 0.08) compounds were synthesized by conventional solid-state reaction followed by spark plasma sintering (SPS) technique. Transport properties of the samples were measured as a function of temperature in the temperature range 323-773 K. As compared to Cu2SnSe3 sample, the electrical resistivity (rho) is increased for the sample with x = 0.04, thereafter a decrease is seen with further increase in copper content. Analysis of electrical resistivity indicates that small poloron hoping model is operative in the entire temperature range for all samples. The positive Seebeck coefficient (S) for the samples in the entire temperature range indicates that the majority charge carriers are holes. The highest figure of merit, ZT (= 0.32) was achieved at 773 K for the sample Cu2.06SnSe3 which is about 3 times that of Cu2SnSe3 sample. Maximum thermoelectric compatibility factor (1.28 V-1) was observed at 673 K for the sample Cu2.08SnSe
Angular and field dependent flux pinning in artificially doped YBCO films on IBAD-MgO based template
No full textThe self-organized artificial pinning structure in superconducting thin films of YBa2Cu3O6+x (YBCO) is optimized on a new type of IBAD-MgO based template by doping YBCO with non-superconducting BaCeO3 (BCO) and BaZrO3 (BZO). In these films, the YBCO is well ordered, no large angle grain boundaries are seen and the isotropic BCO particles are randomly distributed while the BZO grows as unidirectionally splayed and shortened nanorods. Additionally, the low-angle grain boundaries formed during the growth process have an impact on the flux pinning. The flux pinning behaviour can be explained by the vortex path model, where the pinning paths are shorter in BZO doped than in BCO doped films. In BZO doped films, the vortices are pinned with greater pinning force and thus the critical current density J(c) is higher than in BCO doped films, especially in high magnetic fields, where the wide peaks in J(c)(theta) were seen along the YBCO c-direction. This direction dependent pinning can be explained by the nearly similar diameters of BZO nanorods with those of vortices, thus efficiently increasing the vortex pinning in the vicinity of YBCO c-axis