Optimum Polymer Concentration Research Articles

Nanofiber power: Reinforcing in-situ hydrogel for enhanced rivastigmine delivery

Rivastigmine, used in the treatment of Alzheimer's disease (AD), faces challenges of poor stability and low permeability when delivered through conventional methods. To address these issues, rivastigmine-loaded nanofibers were systematically prepared via an electrospinning process utilizing the Design of Experiments (DoE) methodology and subsequently transformed into an in-situ hydrogel using the cold process method. Preliminary experiments determined optimal polymer concentration, ratio, and electrospinning parameters. A 32 factorial design optimized nanofibers, with polyvinyl alcohol (PVA) concentration (X1) and PVA: chitosan ratio (X2) as independent variables, and % cumulative drug release (Y1) and % entrapment efficiency (Y2) as dependent variables. Using the desirability model, the final batch achieved % cumulative drug release and % entrapment efficiency of 90.17 ± 2.64 and 91.46 ± 4.83 respectively. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) studies showed no significant excipient interactions. Field emission scanning electron microscopy (FE-SEM) analysis revealed nanofiber diameters of 160–230 nm. Findings demonstrated that the nanofiber-reinforced in-situ hydrogel exhibited significantly improved gelling capacity at 34.2 °C and increased spreadability (19.51 ± 1.75 cm2) compared to the hydrogel formulations without nanofibers. In-vitro and ex-vivo studies showed controlled rivastigmine release over 8 h. Additionally, enhanced mucoadhesion (236.7 ± 8.83 gm/cm2), pH compatibility (5.9 ± 0.12) with nasal fluid, and moisture resistance uptake highlight suitability for nasal drug delivery. Therefore, this approach offers an efficient delivery platform for rivastigmine with enhanced delivery characteristics and promising therapeutic potential.

Mechanics of dissolving microneedles insertion into the skin: Finite element and experimental analyses

AbstractTransdermal drug delivery using dissolving microneedles (DMNs) is promising due to increased patient compliance and safety. This article presents a comprehensive simulation and experimental analysis of DMNs with varying tip and base diameters and polymers. The objective of the simulation study is to identify the optimal tip and base diameter of DMNs, as well as the most suitable polymer, for achieving maximum penetration depth. The simulation results showed that the compound consisting of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) in a ratio of 2:1, with a tip radius of 17.5 μm and a base radius of 150 μm, achieved the deepest penetration among the different types of polymers investigated (including PVA, hyaluronic acid (HA), and PVA/PVP in ratios of 1:1 and 1:2). In addition, mechanical and skin penetration experiments were performed on PVA/PVP 2:1 DMNs with varying concentrations of 4, 7, 10, and 15% w/w to determine the optimal polymer concentration. The results of this study indicated that the optimal composition, considering the viscosity of the polymer solution and the simplicity of filling the silicone negative molds, is a PVA/PVP 2:1 with a concentration of 7% w/w.

Bubble bursting in a weakly viscoelastic liquid

We study the bursting of bubbles in weakly viscoelastic liquids. The dissolved macromolecules form a monolayer at the water–air interface, influencing the bubble dynamics during the cavity collapse. For an optimum polymer concentration, the interfacial effects dampen short-wavelength waves, which intensifies the focusing of energy powering the jet ejection. This results in a significant increase (decrease) in the first-emitted droplet velocity (radius). The jet formation produces strain rates leading to a significant increase in the extensional viscosity. This extensional thickening reduces (increases) the first-emitted droplet velocity (radius). Bulk viscoelasticity produces a large difference between the velocity of the jet front at the tank surface level and the velocity of the first-emitted droplet. This droplet coalescence with others that are subsequently emitted, even for small polymer concentrations. Overall, viscoelasticity considerably hinders the ejection of small droplets, even for quasi-Newtonian liquids. The droplet emission is suppressed for smaller polymer concentrations when the bubble radius is decreased.

Elucidation on Performance and Structural Properties of Skinned Asymmetric Nanofiltration Membrane Based on Theoretical Models

In this study, the performance and structural properties of enhanced skinned asymmetric nanofiltration (NF) membranes were experimentally and theoretically analyzed. Based on Donnan and steric-hindrance transport mechanism, the relationship of performances and key properties of the fabricated nanofiltration membranes were examined. At the optimum concentration of polymer, the skinned nanofiltration membranes achieved high salt rejection up to 85% and high solutes separation efficacy. Moreover, morphological and modeling analysis discovered that, the optimum membranes produced good pore size and fine key properties with 1.20 nm of pore radius, 4.96 µm of ratio of thickness to porosity (∆x/Ak) and −1.56 of surface charge, ζ as well as uniform pore size distributions. The findings from this study proved that the strategic utilization and manipulation of good membranes material is a simple and good attempt to upgrade the membranes capability and usability which lead towards the application in various membrane separation processes.

Influence of Polymer Concentration on Drying of SPION Dispersions by Electrospinning.

To improve the physical stability of nanoparticle dispersions, several methods for their transformation into stable and easily dispersible dry products have been investigated thus far. Recently, electrospinning was shown to be a novel nanoparticle dispersion drying method, which addresses the crucial challenges of the current drying methods. It is a relatively simple method, but it is affected by various ambient, process, and dispersion parameters, which impact the properties of the electrospun product. The aim of this study was, thus, to investigate the influence of the most important dispersion parameter, namely the total polymer concentration, on the drying method efficiency and the properties of the electrospun product. The formulation was based on a mixture of hydrophilic polymers poloxamer 188 and polyethylene oxide in the weight ratio of 1:1, which is acceptable for potential parenteral application. We showed that the total polymer concentration of prior-drying samples is closely related to their viscosity and conductivity, also affecting the morphology of the electrospun product. However, the change in morphology of the electrospun product does not affect the efficiency of SPION reconstitution from the electrospun product. Regardless of the morphology, the electrospun product is not in powder form and is therefore safer to handle compared to powder nanoformulations. The optimal total polymer concentration in the prior-drying SPION dispersion, which enables the formation of an easily dispersible electrospun product with high SPION-loading (65% (w/w)) and fibrillar morphology, was shown to be 4.2% (w/v).

Preparation of PFPE-Based Polymeric Nanoparticles via Polymerization-Induced Self-Assembly as Contrast Agents for 19F MRI.

Fluorine-19 magnetic resonance imaging (19F MRI) probes have received considerable research interest as imaging contrast agents (CAs), but they remain neglected and underutilized due to the limited fluorine content or poor performance of fluorinated tracers. Here, we present polymeric nanoparticles (NPs) as 19F MRI CAs with a simple synthesis method and promising imaging performance. First, hydrophilic random copolymers were synthesized from oligo(ethylene glycol) methyl ether acrylate and perfluoropolyether methacrylate by reversible addition-fragmentation chain transfer (RAFT) polymerization. The optimal fluorine content, polymer concentration, and cytotoxicity as 19F MRI CAs were investigated in detail. Then, the optimal copolymer was selected as the macromolecular chain transfer agent, and the chain extension was performed with 2-(perfluorooctyl ethyl methacrylate). Subsequently, the NPs with different morphologies, such as ellipsoidal, spherical nanoparticles and vesicles, were prepared in situ by the RAFT-mediated polymerization-induced self-assembly method. In addition, the 19F MRI signal and cytotoxicity studies further confirmed that these polymeric NPs are nontoxic and have great potential as promising 19F MRI CAs for biological applications.

Nanoparticles assisted polymer flooding: Comprehensive assessment and empirical correlation

Conventional Polymer flooding is considered the most promising chemical-enhanced oil recovery by reducing water mobility, and hence increasing the sweep efficiency. However, there are certain drawbacks associated with polymer flooding as the degradation of its molecular structure in severe reservoir environments. Recently, it is experimentally adopted that attachment of nanoparticles (NPs) toward polymer macromolecule may ameliorate the flooding performance and hence increase the oil recovery further than conventional polymer flooding. The potential of NPs assisted polymer flooding has been extensively studied in porous media through core flooding. The target of this work is to statistically scrutinize the previous core flooding experiments and investigate the parameters that affect the incremental oil recovery by NPs assisted polymer flooding. To accomplish this target, a robust investigation of the outcome of over 350 core-flood tests from the literature was gathered to investigate the impacts of rock-oil properties, flooding conditions, polymer, and NPs characteristics on incremental oil recovery. Additionally, Fractional factorial design (FFD) was used to analyze core flood results and screen the effects of reservoir rock, fluid, polymer, and NPs properties on the performance of assisted polymer flooding. Furthermore, an empirical model was built using an Artificial neural network (ANN) to predict the incremental oil recovery for polymeric nanofluid. The results of the investigation indicated that NPs assisted polymer flooding with optimum concentration of both polymer and NPs may result in an incremental recovery of 18% of oil-in-place. Furthermore, the results of FFD revealed that NPs concentration, polymer concentration, and rock permeability are the most significant parameters of oil recovery. The results outcome showed that there is an optimal concentration of both polymer and NPs assisted polymer. In addition, the results revealed that core-flooded viscous oil needs a highly permeable rock to guarantee successful flooding. The coefficient of determination (R2) between the real and calculated incremental oil from the ANN model was established to be 0.953 and 0.952 with an error of 5.6 and 8.7% respectively for the training and testing approaches. Such statistical investigations and ANN approaches afford new insights and guidelines for preliminary assessment, designing, and execution of Nanohybrid polymer upcoming projects on a field scale.

Performance assessment of a novel bio-based polymer for enhanced oil recovery in high salinity sandstone reservoirs

Polymer flooding is arguably the oldest chemical oil recovery method. The use of natural polymers in enhanced oil recovery process has gained wide acceptance due to their excellent viscosity, high resistance to challenging reservoir conditions ranging from increased salinities, temperatures and divalent cations. In recent times, research into the efficiency of green natural polymers is gaining attention as an eco-friendly, readily available and cost-effective option. In this study, the displacement efficiency of Abelmoschus esculentus as a natural polymer in recovering heavy crude from sandstone reservoirs was examined and a simulation model was built to replicate the laboratory model. Abelmoschus esculentus was cleaned, sun-dried, and grinded into powder form and enclosed in an airtight bag. The various phases were analyzed to ascertain the fluid-fluid compatibility and consistency. Polymer rheological studies was conducted at varied temperatures. Core flooding at optimum polymer concentration was considered in an oil-wet sandstone core under reservoir conditions. Results showed that the solubility of the fluids is a function of temperature. Furthermore, polymer viscosity showed a direct relationship to the polymer concentration and temperature. Polymer flooding resulted in additional recovery of 16.26 % oil initially in place (OIIP), thus affirming the efficiency of this natural polymer in recovering heavy oil. However, a viscosity enhancer is required for improved performance. The simulation model was built, and the recovery factors of both models was successfully matched.

Enhancing the flux and salt rejection of thin-film composite nanofiltration membranes prepared on plasma-treated polyethylene using PVA/TS-1 composite

The high hydrophobicity of polyethylene (PE) film restricts its application as a thin-film composite (TFC) support layer. Therefore, in this study, oxygen plasma treatment was used to generate hydrophilic groups on PE and facilitate the formation of the TFC membrane. The difference in the performance of the plasma treated-PE (P-PE) membrane compared to untreated-PE indicated the significant effect of plasma pretreatment. In the following, to enhance the hydrophilicity of the P-PE membrane, titanium silicate-1 (TS-1) was synthesized as a zeotype through the hydrothermal method and added to the aqueous solution of the interfacial polymerization process. Due to the decrease in the agglomeration of TS-1 in the membrane matrix, PVA/TS-1 composites with distinct concentrations of polymer were prepared and applied for modifying membrane properties. Membranes were characterized by FESEM, ATR-FTIR, AFM, zeta potential, and water contact angle analyses. Permeability, rejection of monovalent and divalent salts, and antifouling ability of the fabricated nanofiltration membranes were studied and the optimal polymer concentration was determined. Comparison of P-PE-TFC 0.1 membrane with P-PE showed an increase of ~42% in pure water flux. Also, the rejection of Na2SO4, MgSO4, MgCl2, and NaCl salts were 90.28%, 81.77%, 74.79%, and 70.94% for P-PE-TFC 0.1 membrane, respectively, which showed a notable improvement compared to the P-PE membrane. Evaluation of antifouling ability showed that P-PE-TFC 0.1 membrane had a higher resistance to fouling compared to other membranes. Flux recovery ratio of this membrane after three cycles of bovine serum albumin (BSA) filtration was higher than other membranes resulting from the reduced roughness due to the combined effect of PVA and TS-1.

A Micro-Scale Non-Linear Finite Element Model to Optimize the Mechanical Behavior of Bioprinted Constructs.

Extrusion-based bioprinting is an enabling biofabrication technique that is used to create heterogeneous tissue constructs according to patient-specific geometries and compositions. The optimization of bioinks as per requirements for specific tissue applications is an essential exercise in ensuring clinical translation of the bioprinting technologies. Most notably, optimum hydrogel polymer concentrations are required to ensure adequate mechanical properties of bioprinted constructs without causing significant shear stresses on cells. However, experimental iterations are often tedious for optimizing the bioink properties. In this work, a nonlinear finite element modeling approach has been undertaken to determine the effect of different bioink parameters such as composition, concentration on the range of stresses being experienced by the cells in the bioprinted construct. The stress distribution of the cells at different parts of the constructs has also been modeled. It is found that both bioink chemical compositions and concentrations can substantially alter the stress effects experienced by the cells. Concentrated regions of softer cells near pore regions were found to increase stress concentrations by almost three times compared with stress generated in cells away from the pores. The study provides a method for rapid optimization of bioinks, design of bioprinted constructs, as well as toolpath plans for fabricating constructs with homogenous properties.

Electrospun Azo-Cellulose Fabric: A Smart Polysaccharidic Photo-Actuator.

A natural polysaccharide-based smart photo-actuator is fabricated via electrospinning of cellulose 4-phenyl azobenzoate (Azo-Cel) from its organic solution in a mixture of high-volatile acetone, a poor solvent of Azo-Cel, and low-volatile N,N-dimethylacetamide (DMAc), a good solvent of Azo-Cel. At an optimal polymer concentration (17wt%) and solvent mixing ratio (acetone/DMAc=3/2 (v/v)), stable electrified polymer jets are formed and continuous nanofibers and their nonwoven fabric can be drawn on a cylinder-shaped rotating drum electrode under a high electric field (25kV). Scanning electron microscopic observation of the Azo-Cel fabric confirms that the fabric consists of uniaxially aligned nanofibers with a mean diameter of 207nm. The water contact angle of the Azo-Cel fabric reversibly decreases and increases in response to alternate irradiation with UV and visible light to induce geometric deformation of the azobenzene moiety between the trans and cis isomers, which lead to lower and higher surface free energies, respectively. In addition, self-standing Azo-Cel fabric exhibits a UV-driven photo-mechanical asymmetric bending deformation toward the light source.

Laboratory Studies for Design of a Foam Pilot for Reducing Gas Channeling from Gas Cap in Production Well in Messoyakhskoye Field

Summary This paper highlights the difference between foam injection for gas blocking in production well and injection well and emphasizes the use of polymer enhanced foam. Moreover, this paper shows systematic experimental methods for choosing suitable foam systems for gas blocking in production well considering different factors, which provides a guide regarding what kinds of foaming agents and polymer stabilizers should be used and how to evaluate them for designing a pilot application. The target in this work is the Vostochno-Messoyakhskoye field, operated by Gazpromneft, which is currently experiencing gas channeling from the gas cap in production wells because of strong heterogeneity. Foam has long been considered as a good candidate for gas blocking. However, foam injection for gas blocking in production wells is different from that in injection wells, which requires a long-term impact on gas-saturated highly permeable areas without significantly affecting the phase permeability of oil in the reservoir. Therefore, for gas blocking in production well, a long half-life time of foam is required to sustain stable foam because a continuous shear of surfactant solution/gas cannot be achieved as in injection wells. Thus, reinforced foam by polymer (polymer-foam) is chosen. Four polyacrylamide polymer stabilizers and five anionic surfactants were evaluated using bulk test to determine foaming ability, foam stability, and effect of oil by comparing foam rate and half-life time to determine the suitable foam system with optimal concentrations of reagents. Furthermore, filtration experiments were conducted at reservoir conditions to determine the optimal injection mode by evaluating apparent viscosity, breakthrough pressure gradient, resistance factor, and residual resistance factor. Polymer can significantly improve half-life time (increase foam stability), and the higher the polymer concentration, the longer the half-life time. But simultaneously, a high polymer concentration will increase the initial viscosity of the solution, which not only decreases the foam rate but also increases difficulties in injection. Therefore, an optimal polymer concentration of about 0.15–0.2 wt% is determined considering all these influences. Filtration experiments showed that the apparent viscosity in the core first increased and then decreased with foam quality (the volumetric ratio of gas to total liquid/gas flow). The optimal injection mode is coinjection of surfactant/polymer solution and gas to in-situ generate foam at the optimal foam quality of about 0.65. Filtration experiments on the different permeability cores showed that the gas-blocking ability of polymer-foam is better in high-permeability cores, which is beneficial for blocking high-permeability zone. It should also be noted that under a certain ratio of oil-to-foam solution (about lower than 1 to 1), the presence of high-viscosity crude oil slowly decreased the foam rate with increasing oil volume, but significantly increased the half-life time (i.e., foam stability which is favorable for foam treatment in production well).

Numerical simulation of polymer flooding in water flooding reservoir

Different influencing factors in the process of polymer flooding have different degrees of influence on the development effect, so it is necessary to carry out the dynamic prediction of polymer flooding before implementing the development scheme. In this study, the reservoir model of C Block is established and the production performance is fitted. The fitted reservoir model is used to study the influence of polymer concentration, injection time, injection rate multiple and injection timing on the development effect of C Block. The results show that the cumulative oil production increases gradually with the increase of polymer concentration, and combined with the principle of economic development, there is an optimal polymer concentration in C Block, which is 0.15 wt%; With the increasing of injection time and injection rate multiple, the cumulative oil production and incremental oil production (compared with water flooding) show an increasing trend; For injection timing, the earlier polymer injection is more conducive to obtaining higher cumulative oil production and oil increment. The cumulative oil production under the optimal development scheme of C block is 23.8494×104 m3, which is 1.5042×104 m3 higher than that of water flooding.

The Effect of Polymethylsilsesquioxane Concentration on the Liquid Foundation: Characterization of Nanostructure and Biophysical Properties

Aims: Polymethylsilsesquioxane (PMQS) is a silicone derivative that serves as a skin conditioning agent and moisturizer in cosmetics. The objective of this study is to identify the effect of different concentrations PMSQ (0.12, 0.20 and 0.35 wt %) on liquid foundation (LF) and find the optimized composition in vitro.
 Study Design: Structural and morphological features of the examined nano/micro-sized samples were investigated by different methods.
 Place and Duration of Study: Hacettepe University, Department of Physics Engineering, X-Rays Laboratory, between September 2017 and September 2019.
 Methodology: Micro/nano scale structural and morphological properties of samples were investigated by means of a multi-methodological approach based on Small‐ and/or Wide‐Angle X‐ray Scattering (SWAXS), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM/EDX), Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) Spectroscopy and UV-vis Spectroscopy. The LF (control) and PMSQ-LF films at one-week intervals for 4 weeks, and bovine leather coated samples with LF and PMSQ-LF were also investigated by SWAXS. The effect of PMSQ on biofilm formation activity in E. coli and S. aureus were also examined.
 Results: The most significant finding of this study is that even the low concentration of polymer in LF showed differences in nano structure and it was found that a decrease in biofilm formation. Nano formation becomes more pronounced, and the number of agglomerations decreases after 4 weeks. The reason for the study over a 4-week period was the desire to take into account the independent effect of each LF use, as well as the periodic stacking and diffusing effect that will occur in the depths of the skin over time. In the UVA range (320-400 nm) lower transmittance values were found for LF and PMSQ - LF films. 
 Conclusion: The results suggest that optimum polymer concentration in liquid foundation should be considered as a main step. The smart and systematic use of polymer additives is directly manifested in the nanoscopic structure and can improve the harmful UV rays prevention properties, which are important for health as well as cosmetic effects for beauty purposes.

Comprehensive Effects of Polymer Flooding on Oil–Water Relative Permeabilities

Abstract Many reports have indicated that, in contrast to waterflooding, oil–water relative permeabilities in polymer flooding are influenced by the polymer properties, such as adsorption and viscoelasticity. Long-term injected polymer solutions flush the reservoir porous media causing wettability alteration and residual oil reduction, which is also an important factor for oil–water relative permeabilities. Therefore, the comprehensive effects of polymer properties and dynamic flushing on two-phase percolation behavior have been the focus of research. In this study, polymer flow experiments, including pre-shearing, relative permeability, and long-term erosion tests, were first conducted. Then, a flushing-interpolation model, including polymer concentration interpolation and surface flux characterization, was developed to dynamically describe the two-phase flow characteristics. Based on the experimental results and the presented dynamic model, polymer-flooding simulations were conducted to analyze the performance of the well and the distribution of the remaining oil. The results indicate that flushing reduces the residual oil saturation, and the viscoelasticity effect further broadens the predominant flushing channels horizontally; both effects lead to higher cumulative oil production and a lower water-cut. Additionally, including the flushing effect in the polymer-flooding model leads to a more reliable numerical prediction of the remaining oil distribution. To account for the comprehensive effects of viscoelasticity and erosion in field applications, water-cut history matching was performed for the studied well group, and the error decreased to 4.39%. Finally, the optimal polymer concentration for high-concentration polymer-flooding programs was determined to be 1450 mg/L.

Computer simulation of zwitterionic polymer brush grafted silica nanoparticles to modify polyvinylidene fluoride membrane

Dissipative particle dynamics (DPD) simulations was adopted to investigate the modification of polyvinylidene fluoride (PVDF) membrane by adding zwitterionic polymer brush poly(sulfobetaine methacrylate)- tetraethyl orthosilicate (PSBMA-TEOS) grafted silicon nanoparticles (SNPs) to the casting solution. The effects of polymer concentration and grafting architecture (PSBMA length and SNPs grafting ratio) on membrane morphology are discussed. When the polymer concentration reaches 40%, part of the SNPs is embedded in the membrane; the optimal polymer concentration is around 25–30%. In the SNPs system with the grafting ratio of 1, some SNPs are eluted into solution during phase separation. Compared with different grafting architectures, M8-5, M10-5 and M12-5 system (Mx-y, where x represents the length of the zwitterionic polymer brush and y represents the grafting ratio of the silica nanoparticles) exhibited stable membrane morphologies. This work can provide guidance for the design and modification of organic-inorganic composite membrane and help understand the distribution of modified materials on the membrane surface.

Pressure Drop Reduction in Fluid Flows with a Polymer Solution

This work is targeted at making available some data to enhance the development of better predictive models for drag reduction (DR) in two-phase flows. Oil-water flows studies were carried out by using a horizontal acrylic pipe (14 mm ID) with tap water and a middle distillate oil the flowing liquids. A hydrolysed polyacrylamide served as the polymer in the water phase. Polyethylene oxide (PEO) with two different molecular weights was equally investigated. At an optimal polymer concentration of 20 ppm, drag was lowered as Reynolds number increased. While drag reduction was effectively described by models, it increased with polymer weight.

Synthesis and Stabilization of Gold Nanoparticles Using Water-Soluble Synthetic and Natural Polymers.

Gold nanoparticles (AuNPs) were synthesized and stabilized using the one-pot method and growth seeding, through utilization of synthetic polymers, including poly(N-vinylpyrrolidone) (PVP), poly(ethylene glycol) (PEG), and poly(vinylcaprolactame) (PVCL), as well as natural polysaccharides, including gellan, welan, pectin, and κ-carrageenan. The absorption spectra, average hydrodynamic size, ζ-potential, and morphology of the gold nanoparticles were evaluated based on various factors, such as polymer concentration, molecular mass of polymers, temperature, and storage time. The optimal polymer concentration for stabilization of AuNPs was found to be 4.0 wt % for PVP, 0.5 wt % for gellan, and 0.2 wt % for pectin, welan, and κ-carrageenan. The values of the ζ-potential of polymer-stabilized AuNPs show that their surfaces are negatively charged. Most of the AuNPs are polydisperse particles, though very monodisperse AuNPs were detected in the presence of a 0.5 wt % gellan solution. At a constant polymer concentration of PVP (4 wt %), the average size of the PVP–AuNPs decreased with the decrease of molecular weight, and in the following order: PVP 350 kDa (~25 nm) > PVP 40 kDa (~8 nm) > PVP 10 kDa (~4 nm). The combination of Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy revealed that the functional groups of polymers that are responsible for stabilization of AuNPs are lactam ring in PVP, carboxylic groups in gellan and welan, esterified carboxylic groups in pectin, and SO2 groups in κ-carrageenan. Viscometric and proton nuclear magnetic resonance (1H NMR) spectroscopic measurements showed that the temperature-dependent change in the size of AuNPs, and the gradual increase of the intensity of AuNPs at 550 nm in the presence of gellan, is due to the rigid and disordered conformation of gellan that affects the stabilization of AuNPs. The AuNPs synthesized in the presence of water-soluble polymers were stable over a period of 36 days. Preliminary results on the synthesis and characterization of gold nanorods stabilized by polymers are also presented.

Nature-inspired PDMS cumulonimbus micro-energy-harvesting cloud

Here in this work, nanoenergy-generating films mimicked from cumulonimbus cloud were prepared using deionised water (DI) in polydimethylsiloxane (PDMS). Various characterisation methods have been adopted to verify the content of water as well as the resemblance of the morphological structure of the water-entrapped polymer films with clouds which include scanning electron microscopy and optical reflectance imaging techniques. The water content entrapment in the polymer is verified using the ATR-IR spectroscopy by finding absorbance peaks at 3266 and 1634 cm−1. Polyethylene terephthalate (PET) sheets with a copper coating (Cu-PET) were used as contact electrodes, and the device was fabricated by the simple sandwiching process. Dielectric studies of the device under an applied electric field were used to illustrate the presence of interfacial hopping as well as orientational polarisation in the device. The device fabricated shows an enhancement of 218% and 562% with an increase in water content from 4:1 to 1:1 and a decrease of 26% and 36.5% with a further increase in water for the generated voltage and current measured, respectively. The optimum concentration of polymer to water is selected as 1:1 and the decrease in current and voltage may be due to the condensation of water molecules leading to fewer contact sites between the water and polymer molecules. The devices showed an increment of voltage and current of 171.1 V and 29.16 nA, respectively, with an increase in the force of 1–5 N by using an automated input system. The device was tested under various mechanical inputs, and the generated energy used as sensors in the knock sensor, home doorbell system and seabed vibration detector and as a secondary powering source for charging mobile phones and lighting LED.

Poly (ether) sulfone electrospun nanofibrous membranes embedded with graphene oxide quantum dots with antimicrobial activity.

This work describes the development of novel electrospun nanofibrous membranes (ENMs) prepared by embedding graphene oxide quantum dots (GOQDs) into poly (ether) sulfone (PES). FTIR and Raman spectroscopy confirmed the successful incorporation of the GOQDs into the PES membranes. The optimal electrospinning polymer concentration that showed no defects or bead formation was at 26wt% of the PES polymer. Spectroscopy, microscopy and contact angle were some of the techniques used to characterize the ENMs. SEM images showed smooth and unbranched ENMs. The average diameter upon incorporation of the GOQDs was determined to be 2.45μm. XRD revealed that theGOQDs werestructurally close to graphite with an interlaying space of 0.36nm. The antimicrobial effect of the GOQDs-PES electrospun nanofibrous membranes was assessed against three bacterial strains (Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Bacillus cereus (B. cereus)) using the disc diffusion method. The electrospun nanofibres containing10wt% of GOQDs showed the most active antimicrobial activity against all three bacterial strains tested. The zones of inhibition ranged from 9 to 40mm. The minimum inhibitory concentration (MIC) was determined to be 0.5mg/mL, 0.3mg/mL and 0.2mg/mL for E. coli, B. cereus and S. aureus, respectively. The results demonstrated that incorporating GOQDs in the PES nanofibre gives rise to new antimicrobial properties, and as a result, the GOQDs-PES nanofibrous membrane can be used in antimicrobial applications such as water treatment.