Polyvinylpyrrolidone Matrix Research Articles

Unlocking the Luminescent Potential of Fish-Scale-Derived Carbon Nanoparticles for Multicolor Conversion.

This study introduces a novel approach to addressing environmental issues by developing fish-scale carbon nanoparticles (FSCNPs) with a wide range of colors from discarded fish scales. The process involves hydrothermally synthesizing raw tamban (Sardinella) fish scales sourced from Universal Canning, Inc. in Zamboanga City, Philippines. The optimization of the synthesis was achieved using the response surface methodology with a Box-Behnken design. The resulting FSCNPs exhibited unique structural and chemical properties akin to carbonized polymer dots, enhancing their versatility. The solid-state fluorescence of these nanoparticles can be modulated by varying their concentration in a polyvinylpyrrolidone matrix, yielding colors such as blue, green, yellow, and red-orange with Commission Internationale de l'Eclairage coordinates of (0.23, 0.38), (0.32, 0.43), (0.37, 0.43), and (0.46, 0.48), respectively. An analysis of the luminescence mechanism highlights cross-linking emissions, aggregation-induced emissions, and non-covalent interactions, which contribute to concentration-dependent fluorescence and tunable emission colors. These optical characteristics suggest that FSCNPs have significant potential for diverse applications, particularly in opto-electronic devices.

Preparation and characterization of poly(vinyl pyrrolidone)/cellulose nanofiber/Aloe Vera composites as a biocompatible hydrating facial mask

This study aimed to enhance the properties of polyvinylpyrrolidone (PVP) for use as biocompatible facial masks. To achieve this, nanofibers were developed by blending PVP with cellulose nanofibers (CNFs) and Aloe vera (AV) powder using electrospinning. The results showed that incorporating CNFs and AV into the PVP matrix led to the formation of smooth and uniform nanofibers. In particular, adding 3–6 wt% AV powder in PVP/CNF composites improved fiber diameter distribution and uniformity compared to pure PVP. The PVP/CNF/AV nanofibers exhibited desirable properties for facial mask applications. They displayed 86–93 % porosity, which allowed for efficient moisture absorption capacity of up to 1829 %, and excellent water vapor permeability rate of 3.92 g/m2h. The mechanical properties of the electrospun nanofiber composites were evaluated through tensile testing. The results showed that Young's modulus values decreased progressively with the addition of CNFs and AV powder to the PVP polymer matrix, indicating a plasticizing effect that enhances flexibility. The fracture strain remained similar across all composites, suggesting that CNFs and AV did not significantly weaken the PVP matrix. The tensile strength initially increased with CNF addition but decreased with incremental AV loading. Biocompatibility studies revealed that all nanofibers exhibited excellent fibroblast viability, surpassing 98 %. This indicates that incorporating CNFs and AV did not compromise cell viability, further highlighting the suitability of the PVP/CNF/AV composites for facial mask applications.

Construction of multi‐decay pathways and realizing polymer‐regulated organic smart luminescent materials

AbstractThe construction of multi‐decay pathways of smart organic light‐emitting materials has drawn intensive research enthusiasm owing to their substantial promise in diverse optoelectronic applications. Nowadays, numerous chemical substances have been refined to extend and enhance their intriguing luminescent properties. Nowadays, plenty of chemicals have been adapted to amplify more interesting luminescent properties. How to utilize an easy way to tune multi‐decay pathways resulting in various emissions is still challenging. Here, we present a triphenylamine derivative, TPA3BP, which exhibits a variety of multi‐decay pathways in different states and can exhibit thermally activated delayed fluorescence in both the polydimethylsiloxane and crystalline state, but also achieve room temperature phosphorescence by embedding it into the poly (methyl methacrylate) (PMMA) and polyvinyl pyrrolidone matrix. The multi‐decay luminescence can be attributed to the dual effect arising from the n‐π* transition of TPA3BP and the regulation of molecular transition pathways within the matrix environment. This intriguing phenomenon highlights the combined influence of TPA3BP's electronic transitions and the influence of the polarity and rigidity of the surrounding matrix on the observed characteristics. This advancement has widened the structural possibilities for multi‐decay luminescent materials, enabling their targeted synthesis for future applications, such as information encryption and smart anti‐counterfeiting.

Effect of polyvinylpyrrolidone and lithium chloride composite desiccant-coated heat exchangers on dehumidification studies

Cooling systems are necessities that remain energy intensive, particularly in tropical regions with elevated humidities and temperatures. Conventional vapor-compression air-conditioners are often inefficient because the sensible and latent heat loads are intrinsically coupled. To realize more energy-efficient cooling, solid desiccant-coated devices can be introduced to mitigate the latent heat load. Among such devices, desiccant-coated heat exchangers (DCHEs) are attractive for enabling nearly isothermal dehumidification. Hence, desiccants with high sorption capacity and rapid kinetics are essential. Solid polymeric desiccants are well-positioned to meet these requirements but comprehensive studies on the dehumidification performance of solid polymeric desiccant-coated heat exchangers are currently lacking. In this study, we investigated the potential of polyvinylpyrrolidone (PVP) and lithium chloride (LiCl) composites as desiccant materials at both material and system levels in terms of gravimetric water uptake. Specifically, LiCl is a hygroscopic salt bound by the moisture-sorbing PVP matrix. This work also demonstrates how the Elovich model accurately predicted the PVP-LiCl composite’s sorption kinetics. The results show that the optimum PVP-LiCl composite ratio is 66.7 wt%, with an equilibrium sorption capacity of 280 % at 75 % RH and 25 °C, compared to 29 % for silica gel under the same condition. With much superior sorption kinetics and capacity, the PVP-LiCl-coated prototype heat exchanger demonstrated a moisture removal capacity eight times higher than a silica gel-coated one under dynamic flow towards energy savings in air-conditioning systems.

Investigating the effect of polyvinylpyrrolidone matrix on surface characteristics and dissolution rate of anticancer drug dasatinib

AbstractDasatinib (DAS) is a second‐generation tyrosine kinase inhibitor used in the treatment of Philadelphia chromosome‐positive chronic myeloid leukemia and acute lymphoblastic leukemia. Nevertheless, this drug is hindered by poor gastrointestinal absorption and limited bioavailability, primarily attributable to its low aqueous solubility. To improve its properties, solid dispersions of DAS within a matrix of the hydrophilic polymer polyvinylpyrrolidone (PVP) are prepared by cogrinding in a vibrational ball mill at various drug‐to‐polymer ratios. The prepared solid dispersions are thoroughly characterized by several methods to verify the drug's amorphization and enhanced wettability as a result of successful mechanochemical activation. Fluidized bed melt granulation and traditional tableting are used to prepare tablets of 8 mm diameter with strictly defined aimed properties. Characterization of tablets includes testing their hardness, disintegration, and in vitro dissolution. The in vitro release profiles reveal a significant improvement in the release rate of DAS from tablets containing solid dispersion with the highest polymer ratio when compared with those containing untreated DAS or solid dispersions with a low polymer ratio. The results confirm the significant effect of the PVP ratio in solid dispersions on the surface characteristics and dissolution rate of DAS.

Investigation of the visible-light-driven catalytic activity of nickel oxide-doped carbon nanotubes/polyvinylpyrrolidone nanocomposites towards methylene blue dye

In this study, multi-wall carbon nanotubes (MWCNTs) were wrapped with polyvinylpyrrolidone (PVP) followed by decoration with nickel oxide (NiO) nanoparticles. The composite ofMWCNTs/PVP exhibited an improved capacity for absorbing visible light in comparison to both pristine PVP and MWCNTs alone. Significantly, the ternary nanocomposite of NiO-doped MWCNTs/PVP demonstrated exceptional light absorption in the visible range (400–650 nm). Regarding XRD results, in the PVP pattern, a broad peak at 2θ = 20° implies its semi-crystalline structure. NiO displays diffraction peaks corresponding to the (111), (200), and (220) planes, verifying its crystallinity. Pure MWCNTs exhibit a strong peak at 2θ = 25.62° for the (002) plane, consistent with graphene structure. The MWCNTs/PVP/NiO sample was confirmed by the existence of characteristic peaks for all three components, which indicates successful formation of the triple nanocomposite. The morphological study by FESEM showed that MWCNTs possess diverse nanotube lengths and diameters with concentric graphene layers. In addition, NiO nanoparticles exhibited a uniform, spherical shape with a nanoscale diameter. Finally, the MWCNTs/PVP/NiO sample showed shorter MWCNTs dispersed in a PVP matrix with incorporated NiO nanoparticles. The photodegradation test revealed that pristine MWCNTs show limited photocatalytic performance, while MWCNTs/PVP and MWCNTs/PVP/NiO notably improve dye degradation. The inclusion of NiO nanoparticles, known for their high surface area and light absorption capacity, led to superior methylene blue degradation, underlining their efficacy as photocatalysts.

Development of nanostructured catalysts for catalytic oxidative water purification from organic impurities, including phenolic compounds

The purpose of this work was to create magnetic nanocatalysts that could be used for the oxidation of organic water pollutants – phenol and its derivatives – and to determine the physicochemical characteristics of the catalysts. The development of such active nanocomposite catalysts would solve the environmental problem in the Republic of Kazakhstan in the field of wastewater treatment from organic impurities, including phenols, and would also contribute to the subsequent creation of domestic production of oxygen-containing compounds, since almost the entire spectrum of oxygen-containing compounds for various industries is imported into the Republic. Nanosized magnetic composites based on Fe and Co were obtained by chemical deposition, in some cases, using polyethyleneimine and polyvinylpyrrolidone. It was shown that the interaction between nanoparticles and the polymer takes place in the case of a CoFe2O4 catalyst stabilized with polyvinylpyrrolidone or polyethyleneimine, which may indicate the efficient formation of nanocomposites. According to the IR study, for the CoFe2O4 nanocomposite stabilized with polyvinylpyrrolidone, the absorption bands at 735, 663, 649, 626 cm–1 are natural vibrations for the composite nanoparticles embedded in a polyvinylpyrrolidone matrix. The synthesized nanocomposites were tested in the oxidation of phenol with oxygen. The results demonstrate that the catalysts are promising both for the purification of industrial wastewater from phenol and for the synthesis of oxygen-containing compounds in the liquid phase under mild conditions.

Layer-by-Layer Film Based on Sn3O4 Nanobelts as Sensing Units to Detect Heavy Metals Using a Capacitive Field-Effect Sensor Platform

Lead and nickel, as heavy metals, are still used in industrial processes, and are classified as “environmental health hazards” due to their toxicity and polluting potential. The detection of heavy metals can prevent environmental pollution at toxic levels that are critical to human health. In this sense, the electrolyte–insulator–semiconductor (EIS) field-effect sensor is an attractive sensing platform concerning the fabrication of reusable and robust sensors to detect such substances. This study is aimed to fabricate a sensing unit on an EIS device based on Sn3O4 nanobelts embedded in a polyelectrolyte matrix of polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA) using the layer-by-layer (LbL) technique. The EIS-Sn3O4 sensor exhibited enhanced electrochemical performance for detecting Pb2+ and Ni2+ ions, revealing a higher affinity for Pb2+ ions, with sensitivities of ca. 25.8 mV/decade and 2.4 mV/decade, respectively. Such results indicate that Sn3O4 nanobelts can contemplate a feasible proof-of-concept capacitive field-effect sensor for heavy metal detection, envisaging other future studies focusing on environmental monitoring.

Development of polyvinylpyrrolidone, inorganic nanoparticles, and lithium carbonate nanostructured systems

AbstractNanocomposites with inorganic nanofillers spread in a polymer matrix have been used for the development of pharmaceutical systems to treat mental illnesses such as bipolar disorder and Alzheimer's disease. In this study, nanostructured particles using a solution intercalation technique combined with a spray‐drying process using polyvinylpyrrolidone (PVP), montmorillonite, titanium dioxide, and lithium carbonate, with the aim of designing a new drug delivery system. XRD and low‐field nuclear magnetic resonance analyses showed that PVP/MMT 1% achieved an intercalated/exfoliated morphology. However, the incorporation of TiO2 nanoparticles into the PVP matrix did not affect its structure, indicating that there was not a strong interaction between the polymer and the TiO2 nanoparticles. Thermal analysis did not reveal any changes in the nanocomposites compared to the pure polymer. Scanning electron microscopy (SEM) analysis revealed a pseudo‐spherical shape, and SEM‐energy‐dispersive x‐ray spectrometry (EDS) confirmed the dispersion of MMT in the PVP matrix. The introduction of lithium carbonate into the PVP/MMT matrix created a new system with higher molecular mobility; the drug introduction increased the mean droplet size, and the zeta potential remained negative. Overall, the results indicate that the applied methodology can produce a new nanostructured particle as a drug delivery system.

Optical and morphological properties of ZnO and Alq3 incorporated polymeric thin layers fabricated by the dip-coating method

In this report, we present the influence of polymer matrix on morphological and optical properties of thin films containing zinc oxide (ZnO), tris(8-hydroxyquinolinato)aluminium (Alq3) and ZnO:Alq3. Polyvinylpyrrolidone (PVP) and poly(methyl methacrylate) (PMMA) dissolved in isopropanol and tetrahydrofuran, respectively, were used as polymeric matrices of fabricated composites. The analysed thin layers were deposited on Si substrates using a dip-coating method and characterized by Fourier-Transform Infrared Spectroscopy (FTIR), Energy-Dispersive X-ray spectroscopy (EDX), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Spectroscopic Ellipsometry (SE) and photoluminescence (PL). It was found that adding the polymer to Alq3 causes a blueshift in absorption compared to pure Alq3 layers. We also observed photoluminescence in the region of 2.2–2.8 eV for ZnO:Alq3:PMMA and ZnO:Alq3:PVP, as well as for Alq3:PMMA at room temperature. PL measurements showed that adding ZnO to Alq3:polymer matrix did not result in any shift in PL spectra compared to the results of Alq3:polymer layer. AFM and SEM measurements show that relatively smooth films were obtained in the case of composites based on PVP and PMMA. Moreover, a change in the size of ZnO agglomerates depending on polymer used is observed for the three-component layers. We also noticed that the values of the refractive index are higher for the samples in the PVP matrix. However, the opposite behaviour was observed in the case of the extinction coefficient.

Ciprofloxacin-loaded dissolving polymeric microneedles as a potential therapeutic for the treatment of S. aureus skin infections.

Microneedles have been widely studied for many topical and transdermal therapeutics due to their ability to painlessly puncture the skin, thereby bypassing the stratum corneum, the main skin barrier. In this study, ciprofloxacin (CIP) was loaded into dissolving polymeric microneedles prepared by a two-layer centrifugation method as a potential treatment of skin infections such as cellulitis. The polymers used were polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP). Two formulations were investigated, namely CIP_MN1, composed of 10 mg ciprofloxacin incorporated into a polymer matrix of PVA and PVP with a weight ratio of (9:1), and CIP_MN2, composed of 10 mg ciprofloxacin incorporated into PVA polymer. CIP_MN1 and CIP_MN2 showed a mean microneedle height of 188 and 179 µm, respectively. Since Parafilm has been proven as a model to examine the perforation of microneedles in skin, it was used to evaluate the ability of microneedles to perforate the skin. CIP_MN1 showed almost complete perforation of Parafilm, 190 pores, compared to CIP_MN2 which created only 85 pores in Parafilm, and therefore CIP_MN1 was used for subsequent studies. Examining CIP_MN1 on agarose gel as an in vitro model of human skin showed that the formula was able to fully perforate the agarose gel. Moreover, this formula showed significantly greater antimicrobial activity (p < 0.0001) compared to a free gel of ciprofloxacin against Staphylococcus aureus in an agarose gel-based model. This was evidenced by a zone of inhibition of 29 mm for the microneedle formulation of ciprofloxacin (CIP_MN1) compared to 2 mm for the free gel of ciprofloxacin. Furthermore, the CIP_MN1 showed complete dissolution in human skin after 60 min from application. Finally, the skin deposition of CIP_MN1 was investigated in ex vivo excised human skin. CIP_MN1 showed significantly more deposition of ciprofloxacin in deeper skin layers compared to the free gel of ciprofloxacin, and the released ciprofloxacin from the microneedles tends to migrate to deeper layers with time. Collectively, these results suggest that CIP_MN1 can be a potential delivery system for the treatment of S. aureus skin infections.

Jackfruit Starch Based Blends with Polyvinylpyrrolidone: Preparation, Structural Characterization, and Biodegradable Properties

AbstractStarch is extracted from the seeds of ripen jackfruit (Artocarpus heterophyllus) cultivated in Nepal by treating with distilled water and alkali solution. The properties of extracted starch are evaluated by measuring ash content, moisture content, and amylose content. A series of starch‐based biodegradable blends with polyvinylpyrrolidone (PVP) are prepared through solution casting method and their biodegradable properties are studied. The blend is characterized by thickness measurement, water solubility test, Fourier transform infrared spectroscopy (FTIR), optical microscopy, and biodegradability test. The thickness measurement shows the linear increase in thickness of the blend with the addition of starch. The water solubility test reveals the higher solubility of PVP in water than that of the starch. FTIR spectra of PVP/thermoplastic starch (PVP/TPS) blends exhibit the existence of relevant functional groups of both starch and PVP, the peaks shifting, and the change in nature of the peaks after degradation. Optical microscopy reveals the nonuniform dispersion of starch particles in the PVP matrix and the appearance of holes and fractures in composite subjected to compost soil for degradation. The biodegradability study proves that the loading of starch to PVP accelerates the degradation process.

Nanoarchitectonics of Glass Coatings for Near-Infrared Shielding: From Solid-State Cluster-Based Niobium Chlorides to the Shaping of Nanocomposite Films.

The high potential of [{Nb6Cli12}La6] cluster-based building blocks as near-infrared radiation blockers for energy saving applications is exposed in the present paper (i = inner edge-bridging ligand, a = apical ligand of the Nb6; L = H2O and/or Cl). To do so, a combined experimental and theoretical investigation of edge-bridged [{Nb6Cli12}Cla6-x(H2O)x]m+/0/n- cluster unit series (x = 0, 4, 6; m = 2, 3, 4; n = 2, 3, 4) has been carried out. By using the K4[{Nb6Cli12}Cla6] starting solid-state precursor, we explored the behavior of the [{Nb6Cli12}Cla6]4- cluster unit during the different steps of its integration as a building block into a polyvinylpyrrolidone (PVP) matrix to form a glass coating composite denoted {Nb6Cli12}m+@PVP (m = 2 or 3). The optical, vibrational and redox properties [{Nb6Cli12}Cla6-x(H2O)x]m+/0/n- building blocks have been interpreted with the support of electronic structure calculations and simulation of properties. The chemical modifications and oxidation properties have been identified and studied thanks to various techniques in solution. Combining Raman and ultraviolet-visible spectroscopies, electrochemistry, and quantum chemical simulations, we bring new knowledge to the understanding of the evolution of the properties of the [{Nb6Cli12}Cla6-x(H2O)x]m+/0/n- cluster units as a function of the number of valence electron per cluster (VEC) and the nature of terminal ligands (x = 0, n = 4; x = 4, charge = 0; x = 6, m = 4). The fine understanding of the physical properties and vibrational fingerprints depending on the VEC and chemical modifications in solution are mandatory to master the processing of cluster-based building blocks for the controlled design and shaping of glass coating nanocomposites. On the basis of this acquired knowledge, [{Nb6Cli12}Cla6-x(H2O)x]m+/0/n- building blocks were embedded in a PVP matrix. The resulting {Nb6Cli12}2+@PVP nanocomposite film shows excellent ultraviolet (UV, 280-380 nm) and near-infrared (NIR, 780-1080 nm) blocking ability (>90%) and a highly visible light transmittance thanks to the controlled integration of the {Nb6Cli12}2+ cluster core. The figures of merit (FOM) value of Tvis/Tsol (Tvis = visible transmittance and Tsol = solar transmittance) as well as the haze, clarity, and the NIR shielding values (SNIR) were measured. After optimization of the integration process, a {Nb6Cli12}2+@PVP nanocomposite on glass substrate has been obtained with a high FOM equal to 1.29. This high value places the transparent green olive {Nb6Cli12}2+@PVP nanocomposites at the top system in the benchmark in the field of glass coating composites for energy-saving applications.

Biocompatible nanocomposite production via nanoclays with diverse morphology

Green Nanocomposite Production is conducted in this study; which means that both the production method (water-solvent based) and composite constituents are biocompatible, environmentally-friendly, and non-toxic. Dispersion and thermal behavior of two different nanoclays; tubular Halloysite (HNT) and lamellar Bentonite (BNT) are investigated either individually or mutually in the polymer matrix of Polyvinylpyrrolidone (PVP). For BNT, without any surface modification, exfoliation of silicate layers is achieved owing to the compatible hydrophilic nature of the composite constituents. In the case of HNT nanocomposite, hydrogen bonding between the carbonyl group of PVP and the silanol groups on HNT-surface is detected by Fourier Transformed Infrared Spectroscopy. Thermogravimetric analysis reveals that insertion of either BNT or HNT results in similar improvements in thermal stability (7–8%). However, when HNT surface is modified by 3-aminopropyltrietoxysilane (APTS); the highest thermal stability of this study is achieved and the thermal stability of PVP is enhanced by 11%. This is attributed to the hydrogen bond formation between the amine group on HNT surface and the carbonyl group of PVP. Yet, when BNT is added together with either HNT or APTS-modified HNT, thermal stability improvement is found to be close to the mere addition of unmodified-HNT.

Structural and Infrared Spectroscopy of Polyvinylpyrrolidone/Multi-walled Carbon Nanotubes Nanocomposite

In this work, polyvinylpyrrolidone (PVP)/ Multi-walled carbon nanotubes (MWCNTs) nanocomposites were prepared with two concentrations of MWCNTs by casting method. Morphological, structural characteristics and electrical properties were investigated. The state of MWCNTs dispersion in a PVP matrix was indicated by Field Effect-Scanning Electron Microscopy (FESEM) which showed a uniform dispersion of MWCNTs within the PVP matrix. X-ray Diffraction (XRD) indicate strong bonding of carbonyl groups of PVP composite chains with MWCNTs. Fourier transfer infrared (FTIR) studies shows characteristics of various stretching and bending vibration bands, as well as shifts in some band locations and intensity changes in others. Hall effect was studied to test the type of charge carriers which was shown to be P-type. The electrical conductivity was shown increased for the pure PVP and pure MWCNT from (2.047×10-5) (Ω.cm)-1 and (3.683×101) (Ω.cm)-1 to (2.51×102 and 2.36×102) (Ω.cm)-1for both concentrations of nanocomposites, which indicate the conductivity was enhancement by using the carbon nanotubes.

Investigation of the effect of in-situ grown PPy on low frequency dielectric properties and other properties of PVA-PVP blend film

Present study is carried out to understand the effect of conducting polymer, polypyrrole (PPy) on structural, morphological, thermal and dielectric properties of bio-compatible polymer blend film of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP). The growth of PPy in the matrix of PVA–PVP was analyzed using XRD, FT-IR and SEM studies. The shifting in positions and broadening of XRD diffraction peaks of PVA–PVP-PPy from that of PVA–PVP indicates the structural modification and reduction in the crystallinity of the PVA–PVP due to incorporation of PPy. The SEM studies suggest scattered growth of PPy in PVA–PVP matrix at lower concentration of pyrrole monomer. As the monomer concentration is increased, the uniform and interconnected growth of PPy was observed in SEM micrographs. The TGA thermograms show faster thermal degradation of PVA–PVP- PPy films at lower temperature as compared to PVA–PVP films. The blend films of PVA–PVP- PPy exhibited enhanced values of dielectric constant and ac conductivity as compared to the virgin blend film which are observed to increase with increasing concentration of PPy. The high dielectric constant with high ac conductivity exhibited by PVA–PVP-PPy film suggests its possible application as flexible dielectric material for the development of biosensors, energy storage devices in field of green organic electronics.

Voltage-induced phase transition of VO2@SiO2 nanoparticles

As a typical metal oxide with a strong electronic correlation, vanadium dioxide (VO2) has great application potential in over-pulse protection, new storage devices, and field-effect switches. However, its chemical instability and low dispersibility have restricted its application in these areas. The synthesis of VO2@shell nanoparticles may improve VO2's oxidation resistance. Herein, VO2@SiO2 core-shell nanoparticles with different coating thicknesses are synthesized via the Stöber method. The coated VO2's oxidation temperature is 45 °C higher than that of the uncoated sample. However, the phase-transition temperature of the coated samples remains unaffected (68 °C). A VO2@SiO2 composite material is prepared by mixing VO2 with a polyvinyl pyrrolidone matrix. When the SiO2 coating thickness is less than 3 nm, the composite material undergoes temperature and electro-induced phase transitions. As a result of temperature changes and high voltage application, the resistance of the material can suddenly change. Moreover, the material resistance increases with increasing coating thickness. When the thickness of the material exceeds 3 nm, the room temperature resistance of the material sharply increases. The temperature-induced phase transition of the composite material is not clearly observed. In addition, repeated electro-induced phase transition cannot occur. The nonlinear coefficient of the electro-induced phase transition of the VO2@SiO2 composite material filled with coated particles is improved, particularly when the coating thickness exceeds 2 nm. Our results indicate that SiO2 coating can improve both oxidation resistance and electro-induced phase transition performance of VO2. The optimal coating thickness was between 2 and 3 nm. These findings are of great importance to promote the practical applications of VO2.

Dual-Responsive Thermally Activated Delayed Fluorescence of Spiropyran Derivatives

Dual-Responsive Thermally Activated Delayed Fluorescence of Spiropyran Derivatives

Antibacterial composite coatings of MgB2 powders embedded in PVP matrix

Three commercial powders of MgB2 were tested in vitro by MTS and LDH cytotoxicity tests on the HS27 dermal cell line. Depending on powders, the toxicity concentrations were established in the range of 8.3–33.2 µg/ml. The powder with the lowest toxicity limit was embedded into polyvinylpyrrolidone (PVP), a biocompatible and biodegradable polymer, for two different concentrations. The self-replenishing MgB2-PVP composite materials were coated on substrate materials (plastic foil of the reservoir and silicon tubes) composing a commercial urinary catheter. The influence of the PVP-reference and MgB2-PVP novel coatings on the bacterial growth of Staphylococcus aureus ATCC 25923, Enterococcus faecium DMS 13590, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, in planktonic and biofilm state was assessed in vitro at 6, 24, and 48 h of incubation time. The MgB2-PVP coatings are efficient both against planktonic microbes and microbial biofilms. Results open promising applications for the use of MgB2 in the design of anti-infective strategies for different biomedical devices and systems.

Electronic properties of PVP-ionic liquid composite: spectroscopic and DFT-based thermochemical studies on the effect of anions

Polymer ionic liquid composites are presently an active area of research because of the abounding benefits bestowed by the ionic liquid component to the polymer. They are increasingly investigated as smart materials for multifunctional applications. In this study, the effect of anions, such as Br− and BF4−, having a common N-butylpyridinium (bpy+) cation on the electronic and DFT-based thermochemical properties of polyvinyl pyrrolidone (PVP) polymer was comparatively studied. The PVP-bpy[Br] composites subjected to different thermal conditions were studied using fluorescence spectroscopy, UV–visible spectroscopy, FTIR and Raman spectroscopy. The fluorescence spectroscopic studies showed that bpy[Br] could create efficient electronic trapped states which decreases the electron–hole recombination rate in PVP and partially quenching the PVP fluorescence emission intensity. The PVP fluorescence arising from the C = O electronic transitions is temporarily scavenged by the aromatic pyridinium ring centers. The UV–visible spectroscopic study shows that the optical band-gap of pure PVP is decreased on thermal polymerization in presence of bpy[Br] ionic liquid while it is increased with bpy[BF4−]. The thermochemical calculations indicated that the binding process of bpy[Br] with PVP is spontaneous only at high temperatures and non-spontaneous at low temperatures. The composition analysis using 2D confocal Raman image showed that the use of Br− anions instead of BF4− will give more effective and uniform thermal polymerization of PVP matrix in addition to decreasing its band-gap and making it more conductive. The study indicated that bpy [Br] was a better dopant for PVP than bpy[BF4] and also improved the electronic properties of PVP-based polymer-ionic liquid composites.