Advanced Technologies for Oral Controlled Release: Cyclodextrins for oral controlled release

Cyclodextrins (CDs) are used in oral pharmaceutical formulations, by means of inclusion complexes formation, with the following advantages for the drugs: (1) solubility, dissolution rate, stability and bioavailability enhancement; (2) to modify the drug release site and/or time profile; and (3) to reduce or prevent gastrointestinal side effects and unpleasant smell or taste, to prevent drug-drug or drug-additive interactions, or even to convert oil and liquid drugs into microcrystalline or amorphous powders. A more recent trend focuses on the use of CDs as nanocarriers, a strategy that aims to design versatile delivery systems that can encapsulate drugs with better physicochemical properties for oral delivery. Thus, the aim of this work was to review the applications of the CDs and their hydrophilic derivatives on the solubility enhancement of poorly water soluble drugs in order to increase their dissolution rate and get immediate release, as well as their ability to control (to prolong or to delay) the release of drugs from solid dosage forms, either as complexes with the hydrophilic (e.g. as osmotic pumps) and/ or hydrophobic CDs. New controlled delivery systems based on nanotechonology carriers (nanoparticles and conjugates) have also been reviewed

Antimony-Doped Tin(II) Sulfide Thin Films

Thin-film solar cells made from earth-abundant, inexpensive, and nontoxic materials are needed to replace the current technologies whose widespread use is limited by their use of scarce, costly, and toxic elements. Tin monosulfide (SnS) is a promising candidate for making absorber layers in scalable, inexpensive, and nontoxic solar cells. SnS has always been observed to be a p-type semiconductor. Doping SnS to form an n-type semiconductor would permit the construction of solar cells with p-n homojunctions. This paper reports doping SnS films with antimony, a potential n-type dopant. Small amounts of antimony (1%) were found to greatly increase the electrical resistance of the SnS. The resulting intrinsic SnS(Sb) films could be used for the insulating layer in a p-i-n design for solar cells. Higher concentrations (5%) of antimony did not convert the SnS(Sb) to low-resistivity n-type conductivity, but instead the films retain such a high resistance that the conductivity type could not be determined. Extended X-ray absorption fine structure analysis reveals that the highly doped films contain precipitates of a secondary phase that has chemical bonds characteristic of metallic antimony, rather than the antimony–sulfur bonds found in films with lower concentrations of antimony.United States. Dept. of Energy. Sunshot Initiative (Contract DE-EE0005329)National Science Foundation (U.S.) (Grant CBET-1032955

Spray Pyrolysed Tin Chalcogenide Thin Films: Optimization of optoelectronic properties of SnS for possible photovoltaic application as an absorber layer

In the early 19th century, industrial revolution was fuelled mainly by the development of machine based manufacturing and the increased use of coal. Later on, the focal point shifted to oil, thanks to the mass-production technology, ease of transport/storage and also the (less) environmental issues in comparison with the coal!! By the dawn of 21st century, due to the depletion of oil reserves and pollution resulting from heavy usage of oil the demand for clean energy was on the rising edge. This ever growing demand has propelled research on photovoltaics which has emerged successful and is currently being looked up to as the only solace for meeting our present day energy requirements. The proven PV technology on commercial scale is based on silicon but the recent boom in the demand for photovoltaic modules has in turn created a shortage in supply of silicon. Also the technology is still not accessible to common man. This has onset the research and development work on moderately efficient, eco-friendly and low cost photovoltaic devices (solar cells). Thin film photovoltaic modules have made a breakthrough entry in the PV market on these grounds. Thin films have the potential to revolutionize the present cost structure of solar cells by eliminating the use of the expensive silicon wafers that alone accounts for above 50% of total module manufacturing cost.Well developed thin film photovoltaic technologies are based on amorphous silicon, CdTe and CuInSe2. However the cell fabrication process using amorphous silicon requires handling of very toxic gases (like phosphene, silane and borane) and costly technologies for cell fabrication. In the case of other materials too, there are difficulties like maintaining stoichiometry (especially in large area films), alleged environmental hazards and high cost of indium. Hence there is an urgent need for the development of materials that are easy to prepare, eco-friendly and available in abundance. The work presented in this thesis is an attempt towards the development of a cost-effective, eco-friendly material for thin film solar cells using simple economically viable technique. Sn-based window and absorber layers deposited using Chemical Spray Pyrolysis (CSP) technique have been chosen for the purposeCochin University of Science and TechnologyDepartment of Physics Cochin University of Science and Technolog

Spray Pyrolysed Tin Chalcogenide Thin Films: Optimization of optoelectronic properties of SnS for possible photovoltaic application as an absorber layer

In the early 19th century, industrial revolution was fuelled mainly by the development of machine based manufacturing and the increased use of coal. Later on, the focal point shifted to oil, thanks to the mass-production technology, ease of transport/storage and also the (less) environmental issues in comparison with the coal!! By the dawn of 21st century, due to the depletion of oil reserves and pollution resulting from heavy usage of oil the demand for clean energy was on the rising edge. This ever growing demand has propelled research on photovoltaics which has emerged successful and is currently being looked up to as the only solace for meeting our present day energy requirements. The proven PV technology on commercial scale is based on silicon but the recent boom in the demand for photovoltaic modules has in turn created a shortage in supply of silicon. Also the technology is still not accessible to common man. This has onset the research and development work on moderately efficient, eco-friendly and low cost photovoltaic devices (solar cells). Thin film photovoltaic modules have made a breakthrough entry in the PV market on these grounds. Thin films have the potential to revolutionize the present cost structure of solar cells by eliminating the use of the expensive silicon wafers that alone accounts for above 50% of total module manufacturing cost

Ensuring The Homogeneity OF Spray Pyrolised SnS Thin Films Employing XPS Depth Profiling

SnS thin films were prepared using chemical spray pyrolysis (CSP) technique. p-type SnS films with direct band gap of 1.33 eV and having very high absorption coefficient were obtained with the optimized deposition conditions. In this paper we focus on investigating the uniformity and phase purity of the hence deposited SnS films employing Raman and X-ray Photoelectron Spectroscopy (XPS) analysis. Raman Spectra of the films had only single peak corresponding to the Raman active Ag mode at 224 cm(-1) which is characteristic for phase-pure SnS thin films. Detailed XPS analysis on these samples were performed by scanning the peaks for Sn, S, and O with high resolution to estimate the chemical states and composition. Employing Ar-ion sputtering, the depth profiles showing variation in concentration and binding energies of S, Sn, O over the sample thickness were obtained and the uniformity in composition along the thickness has been discussed in detail

Optimization of parameters of chemical spray pyrolysis technique to get n and p-type layers of SnS

SnS thin films were prepared using automated chemical spray pyrolysis (CSP) technique. Single-phase, p-type, stoichiometric, SnS films with direct band gap of 1.33 eV and having very high absorption coefficient (N105/cm) were deposited at substrate temperature of 375 °C. The role of substrate temperature in determining the optoelectronic and structural properties of SnS films was established and concentration ratios of anionic and cationic precursor solutions were optimized. n-type SnS samples were also prepared using CSP technique at the same substrate temperature of 375 °C, which facilitates sequential deposition of SnS homojunction. A comprehensive analysis of both types of films was done using x-ray diffraction, energy dispersive x-ray analysis, scanning electron microscopy, atomic force microscopy, optical absorption and electrical measurements. Deposition temperatures required for growth of other binary sulfide phases of tin such as SnS2, Sn2S3 were also determinedCochin University of Science and TechnologyThin Solid Films 518 (2010) 4370–437

Role of pH of precursor solution in taming the material properties of spray pyrolysed SnS thin films

Samples were deposited using chemical spray pyrolysis technique by varying the pH of the starting precursor solution from 0.8 to 3.2. These samples were analyzed using X- ray diffraction, optical absorption spectroscopy, energy dispersive X-ray analysis, scanning electron microscopy, and electrical measurements in order to investigate the role of pH of the precursor solution on structural, morphological, electrical and optical properties of the SnS films. From the study we could optimize the pH of precursor solution required for the deposition of device quality SnS thin films. Resistivity of the films was brought down by three orders (to 6 × 10−2 Ω cm) along with enhancement in grain size as well as photosensitivity by optimizing the pH of the precursor solution alone. Band gap of the films could also be tailored by controlling the pH of the precursor solution

Defect levels in SnS thin films prepared using chemical spray pyrolysis

The origin of various defect levels in the SnS thin films deposited using chemical spray pyrolysis (CSP) technique has been explored in this manuscript, by employing low-temperature photoluminescence (PL) technique. Concentration of Sn in the samples was varied purposefully by ex situ diffusion in order to alter the defect levels. The acceptor level obtained at 0.22 eV from the Arrhenius plot, has been assigned as the defect level caused by the Sn vacancies present in the lattice. Two shallow donor levels are conclusively identified and their activation energies have been estimated. The present study could also unearth a trap level in the forbidden energy gap which was due to the oxygen contaminant occupied by the vacancy of Sn. This trap level could be removed by annealing the sample in vacuum or through the ex situ diffusion of Sn. Employing Kelvin probe force microscopy (KPFM), the work-function of SnS was obtained as 4.925 eV, from which the position of the Fermi level could be assigned. Based on the present work, an energy level scheme for SnS thin films is proposed outlying origin of various defect levels