Polypyridyl Ru(II)-sensitizers with extended π-system enhances the performance of dye sensitized solar cells

New polypyridyl ruthenium(II) complexes “cis-Ru(4,4′-dimesityl-2,2′-bipyridine) (Ln) (NCS)₂ H102” and “cis-Ru(4,4′-bis(2,3,6-tri-isopropylphenyl)-2,2′-bipyridine) (Ln) (NCS)₂ H105”, where Ln = 4,4′-dicarboxylic acid-2,2′-bipyridine; were synthesized and successfully applied to sensitization of nano-crystalline TiO₂ based solar cells (DSSCs). The DSSCs of H102 and H105 fabricated from 0.16 cm² TiO₂ electrodes exhibited broader comparable photocurrent action spectra with almost identical solar-to-electrical energy conversion efficiency (η) as compared to N719 sensitizer. The incident photon-to-current conversion efficiency (IPCE) values of 98% and 95% were obtained for H102 and H105 sensitizers respectively. Under 1 sun condition, η-values of 8.39% (short-circuit photocurrent (J_SC) = 16.4 mA/cm², open-circuit photo voltage (V_OC) = 692 mV, fill factor = 0.734), 8.76% (J_SC = 16.3 mA/cm², V_OC = 735 mV, fill factor = 0.734) and 9.12% (J_SC = 16.1 mA/cm², V_OC = 745 mV, fill factor = 0.753) were obtained for H102, H105 and N719 sensitizers respectively.     

A compact tri‐band microwave resonator for ethanol gas detection

This article presents the design, simulation, fabrication, and testing of a compact two‐port microwave resonator coated with nanomaterials for ethanol gas sensing applications. The proposed gas sensor consists of a transmission line loaded with three triangular split ring resonators for ethanol detection at three frequency bands viz. 2.2, 4.6, and 6.3 GHz. The transmission line has all‐pass characteristics in which band gaps are introduced using three split ring resonators. The TiO₂ and ZnO nanorods are used as sensitive layers for the proposed sensing application. The nanorods, which are grown on a glass substrate of thickness 1 mm, are loaded on to the two‐port microwave resonator making the device sensitive to ethanol. The microwave behavior of the sensor is analyzed using the scattering parameters. The absorption of the ethanol gas causes frequency detuning which is used to analyze the presence of ethanol and its concentration. From the experiments, it is understood that there is an increase in the frequency shift with an increase in the concentration of ethanol gas. The sensing device with ZnO as a sensitive layer showed a higher average sensitivity of 2.35 compared to TiO₂ whose average sensitivity is 1.29.     

Targeted biodegradable nanoparticles for drug delivery to smooth muscle cells

Targeted delivery of therapeutic agents to prevent smooth muscle cell (SMC) proliferation is important in averting restenosis (a narrowing of blood vessels). Since platelet derived growth factor (PDGF) receptors are over-expressed in proliferating SMCs after injury from cardiovascular interventions, such as angioplasty and stent implantation, our hypothesis is that conjugation of PDGF-BB (platelet-derived growth factor BB (homodimer)) peptides to biodegradable poly (D,L-lactic-co-glycolide) (PLGA) nanoparticles (NPs) would exhibit an increased uptake of these NPs by proliferating SMCs. In this study, poly (D,L-lactide-co-glycolide) (PLGA) nanoparticles containing dexamethasone were formulated and conjugated with PDGF-BB peptides. These NPs were stable, biocompatible, and exhibited a sustained drug release over 14 days. Various particle uptake studies using HASMCs (human aortic smooth muscle cells) demonstrated that PDGF-BB peptide-conjugated nanoparticles significantly increased cellular uptake and decreased proliferation of HASMCs compared to control nanoparticles (without conjugation of PDGF-BB peptides). These NPs were internalized primarily by clathrin-mediated endocytosis and macropinocytosis. Our in vitro results suggest that PDGF-BB peptide-conjugated NPs could represent as an effective targeted, sustained therapeutic delivery system to reduce restenosis and neointimal hyperplasia.     

Surface functionalization by RF plasma deposition of ethylene diamine,acrylonitrile, and acetonitrile

Surface rich in covalently‐bonded amine groups have wide end use applications in biomaterials. This article describes functionalization of stainless steel (SS) surface with reactive chemical groups using RF‐cold‐plasma polymerization of ethylene diamine (ED), acrylonitrile (AN), and acetonitrile (AcN). The effect of RF plasma power and frequency (40 kHz and 13.56 MHz) on surface chemistry was investigated by electron spectroscopy for chemical analysis (ESCA) and FTIR. It was demonstrated that all the plasma‐deposited films consist of secondary and tertiary amines, imines, and amides with a small concentration of nitrile groups present in AN plasma. Significant changes in ED, and AN plasma‐induced molecular fragmentation occur as the plasma conditions are varied. However, AcN plasma polymer chemistry is observed to be independent of RF frequency. Films deposited at 13.56 MHz RF power in continuous mode have higher concentrations of C? N linkages, with maximum in ED plasma‐polymerized films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Addressing corner detection issues for machine vision based UAV aerial refueling

This paper describes the results of the analysis of specific ‘corner detection’ algorithms within a Machine Vision approach for the problem of aerial refueling for unmanned aerial vehicles. Specifically, the performances of the SUSAN and the Harris corner detection algorithms have been compared. A critical goal of this study was to evaluate the interface of these feature extraction schemes with the successive detection and labeling, and pose estimation schemes in the overall scheme. Closed-loop simulations were performed using a Simulink^®-based simulation environment to reproduce docking maneuvers using the US Air Force refueling boom.     

Effects of poly-(lactide-co-glycolide) nanoparticles on electrophysiological properties of enteroendocrine cells

PLGA nanoparticles are widely used to deliver pharmacological compounds and genes to a variety of cell types. Despite the fact that many of these cells types depend critically on ion channel activity to function normally, there have been no studies on the effect of nanoparticles on the ion channel activity. To this end, we have investigated the effect of nanoparticles on cholecystokinin (CCK)-releasing enteroendocrine cell (EEC) line STC-1. It has been shown that regulation of CCK release from STC-1 cells in response to food depends on the normal electrogenic properties of these cells, including the activity of voltage-gated calcium and potassium channels. Due to the importance of voltage-gated ion channels in the normal physiological responses of STC-1 cells, we performed electrophysiological (patch clamp) experiments to assess the effects of PLGA nanoparticles on the voltage-gated calcium and potassium channels. Whole-cell patch clamp recordings on STC-1 cells containing 100 nm nanoparticles show no macroscopic differences in calcium and potassium channel activity. Additional experiments determined that the activation, inactivation, and use-dependent inactivation of these voltage-gated ion channels did not have any significant effect of nanoparticles on these basic biophysical properties. Lastly, we have examined the effects of PLGA nanoparticles on stimulus-induced rise in intracellular calcium concentration in STC-1 cells, which is necessary for release of CCK. Our data demonstrate that the use of PLGA nanoparticles did not alter the electrophysiological properties of STC-1 cells and supports the use of PLGA nanoparticles as an attractive option for delivering pharmaceuticals/genes to cells of the digestive system that might eventually prove useful for reducing appetite/food intake and in treatment of various gastrointestinal illnesses.     

Triphenylamine-phthalocyanine based sensitizer for sensitization of nanocrystalline TiO2 films

We have designed a new triphenylamine-phthalocyanine based sensitizer (Pc-Org-1) having three bulky triphenylamine groups, which acts as donor and two carboxyl groups, which acts as acceptor as well as servers to graft onto nanocrystalline TiO₂. The new sensitizer was fully characterized by CHN, Mass, UV-Vis, fluorescence spectroscopies and cyclic voltammetry. The bulky triphenylamine groups are further reducing the aggregation of phthalocyanine macrocyle. DFT studies indicate that HOMO is delocalized π-electron system of phthalocyanine and LUMO is located on carboxyl groups. The new photosensitizer was tested in dye-sensitized solar cells using a durable redox electrolyte and compared its performance with PCH001.     

Evaluating the efficacy of amino acids as CO2 capturing agents: a first principles investigation

Comprehension of the basic concepts for the design of systems for CO2 adsorption is imperative for increasing interest in technology for CO2 capture from the effluents. The efficacy of 20 naturally occurring amino acids (AAs) is demonstrated as the most potent CO2 capturing agents in the process of chemical absorption and physisorption through a systematic computational study using highly parametrized M05-2X/6-311+G(d,p) method. The ability of AAs to bind CO2 both in the noncovalent and covalent fashion and presence of multiple adsorption sites with varying magnitude of binding strengths in all 20 AAs makes them as most promising materials in the process of physisorption. The binding energies (BEs) estimating the strength of noncovalent interaction of AAs and CO2 are calculated and results are interpreted in terms of the nature and strength of the various types of cooperative interactions which are present. The study underlines the possibility to engineer the porous solid materials with extended networks by judiciously employing AA chains as linkers which can substantially augment their efficacy. Results show that a significant increase in the CO2···AA affinity is achieved in the case of AAs with polar neutral side chains. Furthermore, the study proposes AAs as effective alternatives to alkanolamines in chemical dissolution of CO2.