PVP Matrix Research Articles

Structural, Optical and Dielectric Properties of Some Nanocomposites Derived from Copper Oxide Nanoparticles Embedded in Poly(vinylpyrrolidone) Matrix.

Polymer nanocomposite films based on poly(vinyl pyrrolidone) incorporated with different amounts of copper oxide (CuO) nanoparticles were prepared by the solution casting technique. The PVP/CuO nanocomposites were analyzed by X-ray diffractometry (XRD), scanning electron microscopy, UV-Visible absorption spectroscopy and dielectric spectroscopy. The XRD analysis showed that the monoclinic structure of cupric oxide was maintained in the PVP host matrix. The key optical parameters, such as optical energy gap Eg, Urbach energy EU, absorption coefficient and refractive index, were estimated based on the UV-Vis data. The optical characteristics of the nanocomposite films revealed that their transmittance and absorption were influenced by the addition of CuO nanoparticles in the PVP matrix. Incorporation of CuO nanoparticles into the PVP matrix led to a significant decrease in band gap energy and an increase in the refractive index. The dielectric and electrical behaviors of the PVP/CuO nanocomposites were analyzed over a frequency range between 10 Hz and 1 MHz. The effect of CuO loading on the dielectric parameters (dielectric constant and dielectric loss) of the metal oxide nanocomposites was also discussed.

CARBON NANOHORNS – BASED NANOCOMPOSITES AS SENSING LAYERS FOR ROOM TEMPERATURE RESISTIVE OXYGEN SENSING: PRELIMINARY RESULTS

This paper presents the oxygen sensing response of a resistive sensor employing sensing layers based on a binary matrix nanocomposite such as carbon nanohorns/polyvinylpyrrolidone and oxidized carbon nanohorns/polyvinylpyrrolidone, both at 9/1 w/w/ mass ratio. The sensing structure comprises a silicon substrate, a SiO2 layer, and interdigitated transducers (IDT) electrodes, on which the sensing layer is deposited via the drop-casting method. The thin film's morphology and composition are examined through scanning electron microscopy (SEM) and RAMAN spectroscopy. The oxygen sensing capability of each carbon nanohorns composite-based sensing layer was analyzed by applying a current between the two electrodes and measuring the voltage difference when varying the O2 from 0% to 100% in dry nitrogen. Experiments reveal that in the case of pristine carbon nanohorns / PVP matrix nanocomposite, the resistance increases. In contrast, in the case of oxidized carbon nanohorns, the resistance of the sensitive layer decreases with increasing oxygen concentration. The results are explained by considering the differences from structural and electrical points of view between the two types of nanocarbonic materials. Moreover, previous resistive RH sensing measurements in humid air and humid nitrogen using oxidized carbon nanohorns as sensing elements proved helpful in better understanding and discriminating between the chemisorption/physisorption of oxygen molecules at carboxyl functional sites and graphitic carbon sites.

Comprehensive study of nanostructured Bi2Te3 thermoelectric materials - insights from synchrotron radiation XRD, XAFS, and XRF techniques.

In this contribution, a comprehensive study of nanostructured Bi2Te3 (BT) thermoelectric material was performed using a combination of synchrotron radiation-based techniques such as XAFS, and XRF, along with some other laboratory techniques such as XRD, XPS, FESEM, and HRTEM. This study aims to track the change in morphological, compositional, average and local/electronic structures of Bi2Te3 of two different phases; nanostructure (thin film) and nanopowders (NPs). Bi2Te3 nanomaterial was fabricated as pellets using zone melting process in a one step process, while Bi2Te3 thin film was deposited on sodalime glass substrate using a vacuum thermal evaporation technique. Synchrotron radiation-based Bi LIII-edge fluorescence-mode X-ray absorption fine structure (XAFS) technique was performed to probe locally the electronic and fine structures of BT thin film around the Bi atom, while transmission-mode XAFS was used for BT NPs distributed in the PVP matrix. The structural features of the collected Bi LIII XANES spectra of thin film and powder samples of BT are compared with the simulated XANES spectrum of BT calculated using FDMNES code at 5 Å cluster size. Combining different off-line structural characterization techniques (XRD, FESEM, XPS, and HRTEM), along with those of synchrotron radiation-based techniques (XAFS and XRF) is necessary for complementary and supported average crystal, chemical, morphological and local electronic structural analyses for unveiling the variation between Bi2Te3 in the nanostructure/thin film and nanopowder morphology, and then connecting between the structural features and functions of BT in two different morphologies. After that, we measured the Seebeck coefficient and the power factor values for both the BT nanopowder and thin film.

A very small amount (0.1 wt%) of Co(OH)2 nanoplates enhances triboelectric performance of polymers

Incorporating 0.1 wt% Co(OH)2 nanoplates into PVP and PU matrix can enhance the triboelectric performance of polymers.

Morphology, luminescence and the gravity sedimentation effect of flexible and highly stable CsPbBr3 nanocrystal patterns by the inkjet printing method

Fine and well-defined CsPbBr3 nanocrystals are in situ crystallized within the flexible and transparent PVP matrix, displaying excellent ambient stability.

Novel evolution of gamma irradiated PVP/Cu–Ag nanocomposite for dye polluted water treatment

A novel polyvinylpyrrolidone/copper–silver (PVP/Cu–Ag) nanocomposite was synthesized via aqueous solution reduction and gamma radiation techniques for the treatment of methylene blue dye (MB) polluted water as a common organic dye pollutant in wastewater which is harmful to human health and aquatic life. Different analyses were used for the characterization of the synthesized Cu–Ag nanoparticles (NPs) and PVP/Cu–Ag nanocomposites such as XRD, TEM, DLS, FTIR, EDX, and TGA The XRD results indicated the typical peaks of CuNPs and AgNPs and the formation of pure crystalline nanoparticles in addition to their corresponding peaks were noticed in the PVP/Cu–Ag nanocomposite. Results of FTIR for the PVP/Cu–Ag nanocomposite confirmed the successful interaction between Cu–Ag NPs and PVP chains. The SEM of the PVP/Cu–Ag nanocomposite appeared rough and dense porous surface with white spots of Cu–Ag nanoparticles that dispersed homogeneously all over the surface of the PVP matrix. The effect of the dose of gamma radiation on the gelation and swelling of PVP hydrogel and PVP/Cu–Ag nanocomposite was studied. Using 15 kGy, the gel content of 89% and 97.1% for PVP and PVP/Cu–Ag, respectively. The swelling degree of PVP/Cu–Ag nanocomposite shows pH dependence and the maximum swelling was at pH 6. The point of zero charge (pHpzc) of PVP/Cu–Ag nanocomposite was 5.8. The factors affecting the removal of MB dye were evaluated as the effect of reaction time, dosage, temperature, pH, and dye concentration. The PVP/Cu–Ag nanocomposite shows fast adsorption of MB dye with a removal percentage of 95% after 50 min, at pH 8, 200 mg/L dye concentration, and 0.1 g nanocomposite dosage. Based on the kinetic, isotherm, and thermodynamic studies, it was found that the adsorption of MB dye onto PVP/Cu–Ag nanocomposite fitted to the Pseudo-second-order kinetic model and the Langmuir isotherm model and the reaction was an endothermic, spontaneous, and chemisorption. The fast removal of the dye using the PVP/Cu–Ag nanocomposite confirms its possible use in wastewater treatment applications as an effective adsorbent for dye treatment.

Optoelectronics characteristics of chemically synthesized Cu(In1-xGax)Se2 based Schottky and heterojunctions

CIGS is an important photovoltaic material in recent years. In this work, we have performed a comparative analysis of various conduction mechanism in CIGSe2 based Schottky and hetero junction nanostructures. Cu(In1-xGax)Se2 nanostructure dispersed in PVP matrix has been synthesized through chemical bath deposition method at a compositional variation x = 0-1. The structural and optical characterization are done and correlated with the In/Ga fraction ratio. The conduction mechanism for both Schottky and hetero structures has been analyses and systematically co-related with compositional variation of In/Ga. By using the thermionic theory, the diode parameters ideality factor, saturation current, barrier height is determined in hetero junction device and co related with composition of Cu(In1-xGax)Se2. Richardson-Schottky(RS) mechanism is found to be dominant in Schottky type junction whereas both Pool-Frenkel(PF) and Richardson-Schottky(RS) mechanism is involved in hetero junction at different range of bias. Our findings points to Cu(In1-xGax)Se2 nanostructures synthesized at x = 0, 0.3,0.5 as promising candidate for solar cell because of their optimum diode parameters and band gap for absorption of maximum solar radiation.

Effects of water molecules on luminescence in europium and terbium coordination polymers with p-fluorobenzoic acid as ligand

Our previous experimental observations show that the crystal structure of lanthanide luminescent complexes synthesized in aqueous solution usually contains a large number of coordination water molecules or free water molecules. In order to probe the influence of water molecules on luminescent processes of lanthanide complexes, the photoluminescence properties of Ln-FBA (Ln = Eu and Tb, FBA = p-fluorobenzoic acid) coordination polymers at different ambient temperatures, in different solvents and aqueous DMSO solutions with different volume concentrations were systematically investigated. The experiment results show that the presence of water molecules can promote the energy transfer from FBA ligand to Ln3+, at the same time, can cause luminescent non-radiation quenching of lanthanide ions. In addition, the variation of emission intensity ratio of 615 nm/591 nm peaks of Eu3+ with increasing the volume concentration of H2O can be potentially used for the quantitatively detection of water traces in organic solvents. In order to suppress the non-radiation quenching caused by the water molecules, Ln-FBA (Ln = Eu and Tb) coordination polymers were embedded into the PVP matrix to prepare Ln-FBA@PVP hybrid materials. The photoluminescence investigation indicates that PVP can not only block the quenching effect of water molecules on luminescence, but also effectively sensitize Eu3+ and Tb3+ luminescence. These experimental conclusions are useful for probing the influence of water molecules on luminescent processes of lanthanide complexes, quantitatively detecting water traces in organic solvents and enhancing the photoluminescence intensity in lanthanide complexes.

Assessment of formulation variables of poor water soluble diacerein for its improved loading and anti-inflammatory activity.

Dissolving microneedles have become a popular method for percutaneous administrationof drugs. However, loading poorly soluble drugs into water-based dissolving microneedles remains a challenge. In view of this, we aimed to improve Diacerein (DCN) solubility formulating dissolving microneedles. DCN microsuspension was created by high-speed homogenization with organic solvents or wet milling with Tween 80 as a stabilizer (LD1). They were analyzed for particle size and saturation solubility. Subsequently, the organic solvent-based microneedles were prepared under vacuum, whereas LD1 was mixed with HPMC (8% w/w) and PVP (30% w/w) matrix to concentrate the drug in acral fraction through centrifugation. DCN microsuspension in DMSO had the highest drug solubility with an average particle size of 6 µm, whereas LD1 had a particle size of 3.28 µm showing improved solubility. TD-3 had the highest drug loading and the least amount of drug migration into the blank baseplate. Within 5 min, these microneedles dissolved completely in an agarose-gel block. LD1 was likewise put in the baseplate to generate TD3-B. Within 24 h, 74.39% of the medication was released from TD3-B, with only a small amount remaining in the baseplate. TLC examination indicated the conversion of DCN to Rhein in the skin, whereas DSC and TGA studies revealed amorphous features. DCN microneedles showed no sign of skin irritancy but showed anti-inflammatory response on carrageenan-induced paw edema model. Microneedles remained stable during accelerated stability testing. Wet milling in the presence of a stabilizer can be an effective approach for enhancing DCN solubility for improved drug loading in dissolving microneedles. Improvement in solubility of Diacerein for subsequent loading in Dissolving Microneedle for percutaneous delivery.

Photo electronic properties of molar concentration varied nanostructured ZnO for their photo-detecting viability in visible range

Zinc Oxide (ZnO) nanoparticle has been synthesized with varying molar concentration by chemical bath deposition method using PVP matrix. HRTEM image clearly exhibits the spherical type particle morphology with average 5 nm size distributions. Optical band gaps of the prepared ZnO nanoparticles are found to be 2.89 eV–3.30 eV on decreasing molar concentration from 1 M to 0.0001 M. The particle size determined PL peak is in well agreement with HRTEM measurement. Photocurrent (I) - light intensity (φ) characteristics exhibits sublinear as well as super linearity behavior. The temperature dependence of conductivity shows two activation energies thatsupport the defect-controlled photoconductivity. The photo detecting parameters at three prime visible lights are determined and correlated with growth. The photo detector parameter increases sharply on lowering molar concentration below 0.1 M and shows a better response to blue light. Thus, ZnO at a lower concentration can explore the suitability of the photo detecting viability in visible range.

Synthesis, Characterization and Luminescence Studies of 3d-4f heterometallic Zinc(II)-Lanthanide(III) Complexes Incorporated in Poly(Vinyl Pyrrolidone) Matrix

A series of Lanthanide complexes Nd(btc).4H2O, Eu(btc).3H2O, Tb(btc).3H2O, Er(btc).H2O, Yb(btc). 3H2O and heterometallic 3d-4f complexes, Nd(btc ) (Zn)(C2H5O)2.5H2O, Eu(btc)(Zn)(C2H5O)2.5H2O, Tb (btc)(Zn)(C2H5O)2.H2O, Er(btc)(Zn)(C2H5O)2.H2O, Yb (btc)(Zn)(C2H5O)2.H2O have been prepared by one step reaction of LnIII and LnIII-ZnII with 1,3,5-benzenetricarboxylic acid (H3btc) by reflux method. All the synthesized complexes were incorporated into poly(vinyl pyrrolidone) (PVP) matrix. All these complexes (1-10) have been characterized by elemental analyses (C,H,N), FT-IR-spectra, Transmission electron microscopy (TEM), fluorescence spectra and powder X-ray diffraction (PXRD) analyses to arrive at conclusion regarding their geometrical structure. Transmission electron microscopy (TEM) showed the shape and size of the complexes, which were homogeneously dispersed in the PVP matrix. TEM results showed the complexes were of rod shaped with a mean diameter about 20 nm. The powder X-ray diffraction (PXRD) patterns of 3d-4f complexes showed well defined crystalline peaks.

The Matrix Effect on Nonlinear Optical Responses of Disperse Orange 25: Optical Bistability and Z-Scan.

The nonlinear behaviours of an azo dye, Disperse Orange 25 (DO25), doped on two polymers (PVP and PMMA), with different weight percentages are investigated under irradiation of 300mW continuous Nd-YAG Laser (λ = 532nm). The optical bistability (OB) of samples was examined using the Mach-Zehnder interferometer. The obtained results show that the PVP matrix doped with DO25 has better nonlinear responses due to their efficiency and stability depend on the properties of the matrix such as the glass transition temperature which is higher for PVP and the structural properties. Also, the third-order refractive index and nonlinear absorption coefficient are measured by (CA) and (OA) Z-scan techniques, respectively.

Modulation of optoelectronic properties of ZnO/PbO core/shell nanocomposite for memcapacitive application

ZnO/PbO core/shell nanocomposites embedded in PVP matrix has been carried out by adopting chemical route with increase in volumetric core/shell ratio. The XRD study shows the hexagonal structure of ZnO and orthorhombic structure of PbO nanocomposites as prime phases. The average grain size and strain are found to increase after coating. Details of structural morphology were analyzed using FESEM and HRTEM techniques. The particle size calculated from HRTEM is found out to be 2.97 and 3.54 nm for ZnO core and ZnO/PbO core/shell nanocomposite respectively which is consistent with those UV–Vis measurements. Absorption studies exhibit the blue shift of the prepared ZnO samples from their bulk counterpart. The absorption edge of the prepared ZnO/PbO core/shells is systematically red shifted from that of core ZnO as the volume of the shell increases whereas the PL intensity reduces after shelling.This effect may be attributed to a systematic decrease of respective band shift at the interface after increase of thickness of shell. Thus, the electrical properties of prepared core/shell nanocomposites act as prominent type II core/shell that can be used as conductive devices. Here the characteristics of mem capacitive devices using ZnO/PbO core/shells have been presented that exhibit promising properties of pinch-off voltage and current with shelling. The I–V measurements show the conduction mechanism is ohmic at low bias and as Richardson-Schottky type in the high bias region. All those structural and optoelectronic optical properties are co-related with the shell thickness for better application in mem-devices.

Study on the third-order nonlinear optical properties of Cd2+ ion doped ZnS/PVP nanocomposite films

Cd2+ ion doped ZnS/PVP nanocomposite films have been prepared using in-situ chemical method. XRD studies confirm the cubic structure of ZnS for all the films. The SEM micrograph shows the mono dispersion of ZnS nanoparticles in PVP matrix. FTIR spectra confirm the formation of nanocomposites containing ZnS nanoparticles and PVP polymer. Optical absorption spectra reveal the blue shift on the absorbance onset with the comparison of bulk ZnS. Photoluminescence spectra show a blue emission peak for all the films. The Z-scan results of all the films show a reverse saturation absorption process in open Z-scan experiment and self-focusing behavior in closed Z-scan experiment. Both ZnS/PVP and Cd2+ ion doped ZnS/PVP films exhibited the large optical nonlinearity and the value of nonlinear refractive index (n2), nonlinear absorption coefficient (β), third-order nonlinear optical susceptibility (χ(3)) and figure of merit (FOM) increase with Cd doping. The estimated n2, β, χ(3) and FOM values are found to be 1.771 × 10−10 m2 W−1, 4.148 × 10−3 mW−1, 1.603 × 10−4 esu and 9.576 × 10−6 esu m 6 mol% Cd doped ZnS/PVP nanocomposite film. The experimental results clearly showed that the Cd2+ ion doped ZnS/PVP nanocomposite film is a worthy candidate for the future nonlinear optical device fabrication.

Ag0 decorated Cr2S3 NPs embedded on PVP matrix: A colorimetric probe for selective and rapid detection of sulphide ions from environmental samples

Globally, the environmental pollution is one of the major issues causing toxicity towards human and aquatic life. We have developed a facile and innovative sensing approach for detection of sulphide ions (S2−) present in the aqueous media using Ag0 decorated Cr2S3 NPs embedded on PVP matrix (Ag/Cr2S3-PVP). Based on the SPR phenomena, the detection of S2− ions was established. The nanohybrid was characterized using various techniques such as UV–vis spectrophotometer, High-Resolution Transmission Electron Microscopy (HR-TEM), Thermal Gravimetric Analysis (TGA), X-ray diffraction analysis(XRD), Energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The yellowish colour of Ag/Cr2S3-PVP nanohybrid turned to brown colour in presence of S2− ions. The selectivity and sensitivity of the prepared probe was studied against the other interfering metal ions. In addition, the effect of different concentration of S2− ions in the nanohybrid solution was investigated and the Limit of detection (LOD) was found to be 6.6 nM. The good linearity was found over the range of 10 nM to 100 μM with R2 value of 0.981. The paper strip based probe was developed for rapid onsite monitoring of S2− ions. The proposed method is found to be cost-effective, rapid, and simple. We have validated the practical applicability of the prepared probe for determining the concentration of S2− ions in real water samples.

Impact of Silver Nanoparticles Synthesized by Irradiated Polyvinylpyrrolidone on Spodoptera littoralis Nucleopolyhedrosis Virus Activity

A Green nanomaterial synthesis could be considered as an alternative bio-controller source of insect pest management as well as saving the environment. Gamma irradiation-induced silver nanoparticles (AgNPs) synthesis in an aqueous solution of irradiated polyvinyl pyrrolidone, (PVP) at ambient conditions was performed. A homogenous mixture solution consisting of (1 mmol Ag+) ions and irradiated (1% PVP) was subject to gamma rays of Co-60 at dose of 20 kGy. Concurrently, the radiolysis of water by γ-rays produced (H2, ehy and H·,OH·) that act as reducing agents and initiators for Ag0 production and PVP polymerization, respectively. The new absorption band observed at 420 nm is confirmed the formation (Ag/PVP) nanoparticles. The color of (AgNO3/PVP) solution converts from colorless to yellowish emphasizing the formation of (Ag/PVP) nanoparticles. The obtained results from X-ray diffraction (XRD) confirmed the coexistence of Ag nanoparticles and PVP matrix. The presence of PVP influenced the shape and distribution of the uniformly dispersed Ag/PVP nanoparticles with diameter 30 ± 5 nm. Bioassay of Ag/PVP nanoparticle on Spodoptera littoralis larvae indicated that the high concentration (600 ppm) of Ag/PVP nanoparticle gave only 11.5% mortality. The interaction between S. littoralis Nucleopolyhedrosis (SpliMNPV) and Ag/PVP nanoparticle had negative correlation to be considered as antagonism. Our finding indicated that the larvicidal activity of Ag/PVP nanoparticle was too low to consider as insecticide against S. littoralis. In the present study, the novelty is reduction of SpliMNPV pathogenicity as well as increased the virus degradation in response to UV irradiation is assisted by Ag/PVP nanoparticle.

Size-Controlled Preparation of Gold Nanoparticles Deposited on Surface-Fibrillated Cellulose Obtained by Citric Acid Modification.

Cellulose-based functional materials have gained immense interest due to their low density, hydrophilicity, chirality, and degradability. So far, a facile and scalable preparation of fibrillated cellulose by treating the hydroxy groups of cellulose with citric acid (F-CAC) has been developed and applied as a reinforcing filler for polypropylene composite. Herein, a size-selective preparation of Au nanoparticles (NPs) stabilized by F-CAC is described. By modifying the conditions of transdeposition method, established in our group previously, a transfer of Au NPs from poly(N-vinyl-2-pyrrolidone) (PVP) to F-CAC proceeded up to 96% transfer efficiency with retaining its cluster sizes in EtOH. Meanwhile, the deposition efficiency drastically decreased in the case of nonmodified cellulose, showing the significance of citric acid modification. A shift of binding energy at Au 4f core level X-ray photoelectron spectroscopy from 82.0 to 83.3 eV indicated that the NPs were stabilized on an F-CAC surface rather than by PVP matrix. The reproducible particle size growth was observed when 2-propanol was used as a solvent instead of EtOH, expanding the range of the available particle size with simple manipulation. The thus-obtained Au:F-CAC nanocatalysts exhibited a catalytic activity toward an aerobic oxidation of 1-indonol in toluene to yield 1-indanone quantitatively and were recyclable at least six times, illustrating high tolerance against organic solvents.

Formation mechanisms of sub-micron pharmaceutical composite particles derived from far- and near-field Raman microscopy

Surface enhanced Raman spectroscopy (SERS) and confocal Raman microscopy are applied to investigate the structure and the molecular arrangement of sub-micron furosemide and polyvinylpyrrolidone (furosemide/PVP) particles produced by spray flash evaporation (SFE). Morphology, size and crystallinity of furosemide/PVP particles are analyzed by scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). Far-field Raman spectra and confocal far-field Raman maps of furosemide/PVP particles are interpreted based on the far-field Raman spectra of pure furosemide and PVP precursors. Confocal far-field Raman microscopy shows that furosemide/PVP particles feature an intermixture of furosemide and PVP molecules at the sub-micron scale. SERS and surface-enhanced confocal Raman microscopy (SECoRM) are performed on furosemide, PVP and furosemide/PVP composite particles sputtered with silver (40 nm). SERS and SECoRM maps reveal that furosemide/PVP particle surfaces mainly consist of PVP molecules. The combination of surface and bulk sensitive analyses reveal that furosemide/PVP sub-micron particles are formed by the agglomeration of primary furosemide nano-crystals embedded in a thin PVP matrix. Interestingly, both far-field Raman microscopy and SECoRM provide molecular information on a statistically-relevant amount of sub-micron particles in a single microscopic map; this combination is thus an effective and time-saving tool for investigating organic sub-micron composites.

Particle properties and drug metastable solubility of simvastatin containing PVP matrix particles prepared by electrospraying technique

In this work the preparation of drug loaded polymeric nanoparticles using electrospraying method and their subsequent characterization is presented. Our purpose was to incorporate the drug with extremely low solubility and low oxidative stability into polyvinylpyrolidone nanoparticles in order to improve its solubility and preserve its chemical stability and hence evaluate the ability of the technology to stabilize such systems in nanoparticulate form. Through the initial screening and optimization of process parameters and polymer solution properties, we detected different morphologies of electrosprayed product particles, where the use of lower molecular weight polymer resulted in a higher process instability as well as in a broader particle size distribution. On the other hand, the solution containing polyvinylpyrolidone with higher molecular weight showed sensitivity to different flow rates and electric field changes, which again resulted in differing the particle size and morphology. The electrosprayed products, prepared by sufficient process stability and having adequately narrow size distribution span, showed lower initial simvastatin contents than theoretically expected, which indicated an oxidative drug degradation already during the electrospraying process. The addition of antioxidants improved simvastatin chemical stability in the particles, during the process itself as well as after accelerated stability study. With an addition of butylated hydroxyanisole antioxidant mixture into initial polymer solution more than 95% of the drug content was preserved after one month at accelerated conditions, whereas in formulations without antioxidants simvastatin content was less than 6%. Antioxidants addition however did not influence only simvastatin stability but also simvastatin solubility. Surprisingly, antioxidants addition did decrease drug solubility in buffers (pH=4 and pH=6.8) for more than a half without any solid state changes of simvastatin. Potential hydrophobic interaction between simvastatin and antioxidants are hindering the drug solubility in the respective buffer, despite drug being in amorphous state.

Effects of cadmium ion concentration on the optical and photo-response properties of CdSe/PVP nanocomposites for white light sensing application

Cadmium selenide (CdSe) nanoparticles dispersed in the PVP matrix with varying concentrations of cadmium (Cd) ion complex have been synthesized through a low-cost chemical bath deposition technique to investigate the effects of cadmium ion concentration on its optical and photo-response characteristics. To confirm the formation of pure, stable, well dispersed, and highly crystalline spherical CdSe nanocomposites different characterization techniques such as X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and Fourier transform infrared spectroscopy have been used. The optical band gaps and sizes of the nanocomposites are determined from the UV–Vis data while the surface-related emission properties of the CdSe nanocomposites are obtained from the PL data. The quantum confinement on the CdSe nanocomposites increases with the decrease of Cd ion concentration. I–V characteristics measurements have been done on the samples to investigate the photo-response properties of the samples. Various optical properties such as bandgap, near bandgap emission, and impurity emission are correlated with the photo-response properties of the samples. The photoresponse properties are found to become more suitable for application in white light photosensor with the increase of quantum confinement. Mechanisms related to the enhancement of photocurrent with respect to quantum confinement are also discussed in this paper.