Search

We undertook this present study; a simple and straight forward approach is developed to achieve CdSe/ZnS core-shell quantum dots by hydrothermal method and change the different hydrazine hydrate concentrations. As prepared QDs were characterized by high-throughput techniques and are tested for cytotoxicity activity against breast cancer cell line (MDA-MB-231) and testing in to sensitized solar cells (QDSSC) respectively. Further, the results study also revealed that, CdSe/ZnS QDs display unique tunable size, which is evidenced by transmission electron microscopic studies and optical properties (UV-Visible) studies. Moreover, FT-IR spectral investigations provide information about the interaction of trisodium citrate and hydrazine hydrate role in the surface functionalization and found plausible reason. The hydrazine hydrate modified CdSe/ZnS QDs (CZT-10) show an impressive anticancer activity in breast cancer cells and photovoltaic efficiency. This study open new avenues to find vital play on development of nanomaterial in the field of energy and environment application.

Silver-impregnated polyacrylonitrile (PAN) nanofibre was prepared through electrospinning process. Infra-red spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Thermo gravimetric analyses (TGA/DTA) were used to characterize PAN and PAN/Ag composites. The XRD results reflects decrease in the crystallinity of PAN as it is been modified with Ag. Antibacterial activity of PAN/Ag was also investigated.

A report is given of the systematic investigation on the glass stability and conduction characteristics of binary lithium germanate glasses in the series, mol% xLi2O-(100-x)GeO2, 5 ≤ x ≤ 30. The glass stability (against devitrification) parameters along with density and glass transition temperature reveal an extremum around 15 mol% of Li2O, a signature of the germanate anomaly. The analysis of impedance data in conductivity and modulus formalisms reflect different aspects of the structural changes as the amount of Li2O increases. The lithium ion conductivity increases with the increase in the Li2O concentration while the activation energy for ionic motion does not change much from mol% 5 to 10 Li2O and decreases monotonically from mol% 10 to 30 Li2O indicating the absence of germanate anomaly. However, the data in modulus formalism does not scale to a master curve for all the glasses suggesting the germanate anomaly. Modeling of the modulus data using the Kohlrausch-Williams-Watts (KWW) function depicts the germanate anomaly in the stretched exponential parameter (β) at 15 mol% Li2O. Raman spectra of the glasses reveal the preferential formation of Q2 units at low alkali concentration along with the formation of ring structures of several Ge tetrahedra and/or the formation of higher coordinated Ge species around the anomalous composition region. A correlation of these structural changes with the conduction characteristics of the glasses is also discussed.

Current treatment strategy for end stage valve disease involves either valvular repair or replacement with homograft/mechanical/bioprosthetic valves. In cases of recurrent stenosis/ regurgitation, valve replacement is preferred choice of treatment over valvular repair. Currently available mechanical valves primarily provide durability whereas bioprosthetic valves have superior tissue compatibility but both lack remodelling and regenerative properties making their utility limited in paediatric patients. With advances in tissue engineering, attempts have been made to fabricate valves with regenerative potential using various polymers, decellularized tissues and hybrid scaffolds. To engineer an ideal heart valve, decellularized bovine pericardium extracellular matrix (DBPECM) is an attractive biocompatible scaffold but has weak mechanical properties and rapid degradation. However, DBPECM can be modified with synthetic polymers to enhance its mechanical properties. In this study, we developed a Bio-Hybrid scaffold with non-cross linked DBPECM in its native structure coated with a layer of Polycaprolactone-Chitosan (PCL-CH) nanofibers that displayed superior mechanical properties. Surface and functional studies demonstrated integration of PCL-CH to the DBPECM with enhanced bio and hemocompatibility. This engineered Bio-Hybrid scaffold exhibited most of the physical, biochemical and functional properties of the native valve that makes it an ideal scaffold for fabrication of cardiac valve with regenerative potential.

In this report, ZnO nanoparticles embedded cellulose acetate (CA) fibrous membrane with multifunctional properties have been prepared through electrospinning method. The morphology of the electrospun composite membrane was analyzed by scanning electron microscope (SEM). It was found that the polymer concentration in the solution has a significant effect on the morphology of the fibers. The optical property of the sample was tested using photo luminescence (PL) spectra. There is no significant change in the emission features of cellulose acetate with the addition of ZnO. The anti-bacterial property of the sample was studied using disk diffusion method. The wettability of the pure and composite fibrous membrane was also studied by measuring the contact angle of water on the membrane. It was observed that the embedded ZnO in the CA was responsible for the hydrophobic nature of the surface. � 2013 Elsevier Ltd. All rights reserved.

A simple, low-cost and sensitive UV sensor based on electrospun composite fibers was fabricated. Three different types of (PVA/ZnO) composites were used to fabricate the device. The solution-cast film of PVA and ZnO shows lower photocurrent than the other two fiber based devices. A comparative photoresponse study has revealed the high sensitiveness of the in situ derived composite fibers of PVA and ZnO under UV illumination thus making them highly suitable for the fabrication of UV detector. We believe that the coupled effect arising from the presence of PVA and uniform distribution of ZnO are responsible for the sensitivity of UV sensor. Thus we conclude that the response of UV sensor is highly dependent on the morphology of the composites and the preparation method. � 2012 Elsevier B.V.

One dimensional nanofibers of organic and inorganic materials have been used in filters, optoelectronic devices, sensors etc. It is difficult to obtain ultra fine fibers of inorganic materials having lengths in the order of millimeter as they tend to break during formation due to thermal and other mechanical stresses. In this study, we have investigated the mechanism to prevent the defect formation and the breaking ZnO nanofibers by using optimized heat flow rates. ZnO nanofibers were obtained by heat treating the PVA composites fibers formed by electrospinning. The morphology and structural characteristic of prepared samples were investigated by Scanning electron microscopy and X-ray diffraction. It was found that the morphology of the composite and annealed nanofibers could be influenced by the concentration of the polymer content and heat flow rate during thermal treatment respectively. A lower concentration favors the formation of defects along the fiber and the number of defects reduces when the concentration is increased. The reasons for the formation of defects and their reduction, and the observed structural changes of ZnO nanofibers during heat treatment are also discussed. � 2010 Elsevier B.V. All rights reserved.

Electrospinning is a versatile method of preparing polymer nanocmposite fibers. Electrospun nanocomposite fibers of poly(methyl methacrylate) and single walled carbon nanotubes were prepared. The fibers were characterized by SEM, TEM, TGA and Raman spectroscopy. These fibers show dramatic improvement in the electrical conductivity compared to the polymer. The temperature dependent electrical resistance measurements show a one dimensional variable range hopping model (1-D VRH) type of conduction mechanism operating in these types of systems.

Measurements of d.c. electrical conductivity (σ) as a function of temperature and electric field on heat-treated poly metallo phthalocyanines II[MPc] n (M = Co) are reported. The temperature dependence of σ is in accordance with the variable range hopping in three-dimensions for different electric fields. The electric field dependence of resistivity obeys a relation of the form ϱ = kE m .

Here we report, the preparation of flexible free standing Fibrous Composite Membrane (FCM) of PVA-ZnO by combined sol-gel and Electrospinning method. The morphology of the sample was investigated by SEM and TEM which confirmed the uniform distribution of ZnO on the surface of the fiber without much of aggregation. The high purity of the sample was proven by photoluminescence studies. Evaluation of antibacterial properties of the sample against both Gram-positive and Gram-negative bacteria, showed that the prepared sample by this method is most effective for Methicillin-resistant Staphylococcus aureus. The mechanism responsible for the bactericidal effect of ZnO has been discussed. The unique properties of the FCM would be highly significant for applications in antimicrobial coatings, UV sensors etc. � 2012 American Scientific Publishers All rights reserved.

The market demand for new devices and gadgets is ever increasing; this applies enormous pressure on researchers all over the world who are engaged in materials science to come up with new materials such as polymers and ceramics, as alternatives to the conventional inorganic materials like silicon and gallium arsenide. In addition to this, recent developments in device geometries have been moving toward using even smaller materials, namely from 2-D thin films to 1-D fibers, tubes, rods and even zero-dimensional quantum dots, etc. In this context, this chapter attempts to review the recent research trends in the fabrication of fibers by a specialized but simple process of electrospinning, and the applications of such functionalized nanofibers in the area of new electronic devices.

Fabrication of ultraviolet light emitting devices using ZnO nanostructures is still difficult due to the high cost synthesis for high quality ZnO. It is important to suppress the visible emission. In this paper, we report the effective low cost in-situ preparation of high quality monodispersed and non-agglomerate ZnO nanoparticles in nanofibrous PVA matrix derived from electrospinning method. The final product was investigated by SEM, EDAX, XRD, FTIR, TEM, and SAED. The XRD analysis proved the successful preparation of ZnO with wurtzite hexagonal phase. FTIR spectroscopic measurements showed the interaction between ZnO and PVA. The purity of the sample was studied using PL. The result showed that the obtained sample exhibits intense ultraviolet emissions at 369 nm while the absence of deep level emission confirms the high quality sample. PVA matrix and electrospinning method are found to have a vital role to the preparation of defect free ZnO. Experimental results have proven that the prepared ZnO by this method have excellent optical quality. � 2011 Elsevier B.V. All Rights Reserved.

Here we report an approach to fabricate flexible polymer self standing films embedded with continuous aligned microtubes/microchannels via electrospinning. The scheme is to wash the electrospun fibers selectively to form either microtubes/microchannels. Optical microscope (OM) and Scanning electron microscope images are evident for the well aligned microtubes and microchannels respectively with a diameter of ?8 ?m and a length of ?4 cm. Meniscus of tetrahydrofuran in the microtubes can be observed explicitly in the OM images. Mutually perpendicular microtubes are also fabricated on a polymer film. Angular distribution of aligned microstructures indicates the standard deviation is not more than 1�. These tubes/channels can be potential for tissue engineering as they could provide a directional template for the growth when a biodegradable polymer such as Poly(vinylalcohol) is used. � 2011 Elsevier B.V. All rights reserved.

The authors describe the design of an automatic controller, based on the Intel 8748 single-chip microprocessor, for a Stirling cycle nitrogen liquefying plant. The microcontroller has a real-time clock and a battery back-up system to monitor mains power failures and takes corrective action after the restoration of power. It controls the plant automatically without requiring the presence of an operator round the clock. The plant was automated by using solenoid valves at specific points to control electrically the existing manual valves. The controller continuously monitors the various subsystems such as cooling water flow rate, the pressure of the lubricant oil, etc., and switches off the plant when an error condition is detected. It displays in such cases a single digit error code corresponding to the error detected. It waits in a check-loop until the error is rectified by an operator and then starts the plant automatically. >

The previously reported measurements of the dc electrical conductivity σ for heat treated poly copper phthalocyanine (II[CuPc]n) were extended down to 4.2 K. The significant deviation from linearity of the log (σ√T) versus T - 1 4 plot at low temperatures can be accounted for by the model proposed by Sheng which is based on electron transfer across insulating gaps in conducting pathways by fluctuation induced tunneling.

The design of a microprocessor-based resistivity measurement system for high transition temperature (T/sub c/) superconducting materials is described. This design includes interfacing an Intel 8085 microprocessor system with an IBM-compatible personal computer (PC) through RS-232C serial communication. This design is used to measure resistivity for superconducting samples of YBa/sub 2/Cu/sub 3/O/sub 7-x/ and strontium/potassium substituted YBa/sub 2/Cu/sub 3/O/sub 7-x/. A correction method is described for the parameters whose values are changing throughout the measurement period to minimize the measurement errors. >

The dipole correlation function of three esters of crotonic acid have been computed from the infrared absorption bands. Both short-time and long-time behaviour of the correlation functions are computed and discussed. The correlation times are also calculated. The short-time behaviour was compared with the correlation functions generated as an even-power series with second and fourth moments. They were also compared with the correlation functions of the freely rotating molecule.