Stabilizer Polyvinylpyrrolidone Research Articles

The Synthesis and Assembly Mechanism of Micro/Nano-Sized Polystyrene Spheres and Their Application in Subwavelength Structures

The following study involved the utilization of dispersion polymerization to synthesize micron/nano-sized polystyrene (PS) spheres, which were then deposited onto a silicon substrate using the floating assembly method to form a long-range monolayer. Subsequently, dry etching techniques were utilized to create subwavelength structures. The adjustment of the stabilizer polyvinylpyrrolidone (PVP), together with changes in the monomer concentration, yielded PS spheres ranging from 500 nm to 5.6 μm in diameter. These PS spheres were suspended in a mixture of alcohol and deionized water before being arranged using the floating assembly method. The resulting tightly packed particle arrangement is attributed to van der Waals forces, Coulomb electrostatic forces between the PS spheres, and surface tension effects. The interplay of these forces was analyzed to comprehend the resulting structure. Dry etching, utilizing the PS spheres as masks, enabled the exploration of the effects of etching parameters on the resultant structures. Unlike traditional dry etching methods controlling RF power and etching gases, in the present study, we focused on adjusting the oxygen flow rate to achieve cylindrical, conical, and parabolic etched structures.

Synthesis of Modified Polyvinyl Pyrrolidone (PVP) Silver Nanoparticles Using Soursop (Annona muricata Linn) Leaf Extract and Its Application as a Heavy Metal Colorimetric Sensor

This study aims to analyze the characteristics and performance of silver nanoparticles (AgNP) synthesized using soursop leaf extract bioreductor modified with the addition of polyvinyl pyrrolidone (PVP) stabilizer as a colorimetric sensor for heavy metal ions. The synthesis of silver nanoparticles was carried out by reducing AgNO3 using soursop leaf extract (Annona muricata Linn) bioreductor modified with the addition of PVP as stabilizer. The results showed that the optimum synthesis volume ratio of AgNP synthesis was 0.7 mL of soursop leaf extract: 10 mL AgNO3 with the addition of 3% PVP stabilizer. The formation of AgNP was characterized by a change in the color of the solution from yellow to brownish with a surface plasmon resonance peak at a maximum wavelength of 438 nm. Fourier-transform infrared spectroscopy studies showed hydroxyl groups (-OH) and carbonyl groups (C=O) play a role in the reduction process of silver ions. Particle size analysis results demonstrated an average particle size of 71.5 nm with a polydispersity index value of 0.364. The results of the colorimetric analysis showed that the synthesized AgNPs proved to be highly selective towards Cu metal ions.

Preparation of Tetrandrine Nanocrystals by Microfluidic Method and Its In Vitro and In Vivo Evaluation.

The anti-hepatocellular carcinoma effects of TET are acknowledged, but its application is hindered by its poor water solubility and low bioavailability. Conventional methods for nanocrystal preparation are laborious and lack control. To address these limitations, we propose employing the microfluidic method in the preparation of TET nanocrystals, aiming to enhance the aforementioned constraints. The objectives of this study were to prepare TET nanocrystals (TET-NC@GL) using a Y-microfluidic method with glycyrrhetinic acid (GL) as a stabilizer. The optimal preparation prescription was determined through a single-factor test and Box-Behnken response surface method. Additionally, the nanocrystals prepared with the commonly used stabilizer polyvinylpyrrolidone K30 (PVPK30), known as TET-NC@PVPK30, were characterized and evaluated for their toxicity to HepG2 cells. Hybridized nanocrystals (TET-HNC@GL and TET-HNC@PVPK30) were synthesized using a water-soluble aggregation-induced emission (AIE) fluorescent probe (TVP). Qualitative and quantitative cellular uptake experiments were conducted using these hybridized nanocrystals. Conducting in vivo pharmacokinetic assays evaluates the relative bioavailability of nanocrystals. The results indicated that TET-NC@GL, optimized using the response surface method, had a particle size of 136.47 ± 3.31nm and a PDI of 0.219 ± 0.002. The administration of TET-NC@GL significantly enhanced the cell inhibition rate compared to the TET group and the TET-NC@PVPK30 group (P < 0.01). Moreover, the qualitative and quantitative cellular uptake results revealed a significant enhancement in cellular uptake in the TET-HNC@GL administration group compared to the TET-HNC@PVPK30 group (P < 0.01). In vivo pharmacokinetic results showed that the bioavailability of TET-NC@GL group was 3.5 times higher than that of the TET group. The results demonstrate the successful preparation of TET-NC@GL nanocrystals.

CYCLOBIS(PARAQUAT-P-PHENYLENE) - MEDIATED ELECTROSYNTHESIS OF SILVER NANOPARTICLES

Silver nanoparticles (Ag-NP) were obtained in MeCN/0.05 M Bu4NPF6 medium by сyclobis(paraquat-p-phenylene) (CBPQT4+) – mediated reduction of the silver ions generated by anodic oxidation of metallic silver during the electrolysis in an undivided cell. Due to multipoint donor-acceptor interaction CBPQT4+ binds the resulting electron-donor Ag-NP to each other, which leads to their enlargement, aggregation and adsorption. This property of the macrocycle allows to call it a “molecular glue” for NP-Ag. In the absence of stabilizers, aggregated polydisperse Ag-NP of indefinite shape are formed with sizes ranging from 20 to 500 nm. Electrosynthesis in the presence of a stabilizer, polyvinylpyrrolidone (PVP), also leads to the formation of aggregated smaller metal particles of 55 ± 26 nm, which have, in addition to the quasi-spherical shape, the shape of a flat triangle and hexagon. Ag-NP stabilized by PVP are partially bound on the surface of nanocellulose (NC). In the presence of NC, larger Ag-NP with an average size of 97 ± 29 nm are formed, the main shape of which is quasi-spherical; cubic, tetrahedral, and rod-shaped Ag-NP are also formed; the formation of Ag-NP with a flat structure is excluded. The catalytic activity of the obtained particles in the reduction of p-nitrophenol with sodium borohydride is extremely low due to the large size, aggregation, and coating of the NP-Ag surface with the stabilizer PVP and marcocycle.

Fabrication of Magnetic Silica Nanomaterials and Their Effects on Algal Harvesting

Harmful algal blooms are a global problem in water environments, and their explosive growth endangers the health of aquatic ecosystems. Magnetic nanomaterials for the harvesting of microalgae have received a lot of attention because of their high efficiency, low cost, and ease of operation. In this study, magnetic mesoporous silica nanomaterials were prepared using Fe3O4 as a carrier and harvesting on Chlorella sp. HQ. It was found that silica coated with magnetic Fe3O4 microspheres has good dispersion. The harvesting of Chlorella sp. HQ via magnetic mesoporous silica could be maintained over a wide pH range (4 to 12). After the removal of organic components from the surface of the material, the magnetic mesoporous silica obtained a better porous structure. The ethanol reflux method was more beneficial than the calcination method in maintaining the stable structure of the material, thus improving the harvesting efficiency of the material for the microalgae Chlorella sp. HQ by a maximum of 17.8% (65.9% to 83.7%). When the molar ratio of active agent cetyltrimethylammonium bromide (CTAB) and stabilizer polyvinylpyrrolidone (PVP) was 1: 0.092 at pH 4 and algal concentration of 0.5 g/L, the materials showed the maximum harvesting efficiency of Chlorella sp. HQ was 84.2%.

Surface oxygen vacancies promoted Pt nanoparticles on celery-like CeO2 nanofibers for enhanced sinter-resistance and catalytic performance

Supported metal nanoparticles hold great promise for heterogeneous catalysis but are greatly persecuted by the poor thermal stability upon high temperatures. In this work, we facilely synthesized intriguing celery-like CeO2 nanofibers with high surface areas and hierarchical pores and channels by single-spinneret electrospinning. The nanofibers were explored as reliable support for polyvinylpyrrolidone (PVP)-stabilized Pt nanoparticles, followed by activation at 350 °C in N2 to eliminate PVP stabilizer and generate sufficient surface oxygen vacancies. Therefore, the resultant Pt@CeO2 was endowed with enhanced metal−support interaction and thereby promoted sinter-resistance. In this case, the Pt@CeO2 exhibited over six times higher activity after aging at 600 °C toward the hydrogenation of p-nitrophenol than that of PtPVP/CeO2. Moreover, the thermal-stable Pt@CeO2 significantly decreased the activation energy of soot oxidation from 178.0 kJ/mol to 109.4 kJ/mol, due to the abundant oxygen vacancies, as well as the promoted solid–solid contact by the interconnected and celery-like CeO2 nanofibers. After such a sinter-promoting exothermic reaction, the supported Pt nanoparticles maintained a small size of 5.78 nm. This approach provides a facile method to prepare noble metal catalysts with both high atom economy and sinterresistance.

SnS-Nanocatalyst: Malachite green degradation and electrochemical sensor studies

The photocatalytic degradation of the toxic dye malachite green (MG), has been investigated using visible light responsive tin sulfide (SnS) nanocatalysts and details of degradation intermediates were obtained by liquid chromatography-mass spectrometry (LC-MS). Excellent photo-degradation efficiency of 99% and 98% is achieved within 75 min by using SnS nanoparticles (NPs) having an orthorhombic and cubic crystal structure, respectively. Microstructure of the synthesized SnS nanoparticles (NPs) were examined by high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED). The oxidation states of SnS NPs were analyzed by X-ray photoelectron (XPS) spectroscopy. The stabilizer polyvinyl pyrrolidone (PVP) was found to have pronounced effect on the crystallinity and morphology of the nanoparticles. Thirty-four intermediate products from the degradation of malachite green were identified by LC-MS analysis, and their structural details, chemical name, observed molecular mass, retention time and degradation mechanisms are summarized. Electrochemical analysis showed excellent performance in redox potential measured by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Further, SnS NPs extended their electrochemical sensor activities to detect lead acetate, a heavy metal chemical present in the water. The prepared SnS/LDPE floating catalyst has advantage of easy recovery and thereby its potential to re-use in treating textile and dying industry wastewater.

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.

Effect of ethylene carbonate on properties of PVP-CsAlO2-LiClO4 solid polymer electrolytes

ABSTRACT Solid polymer electrolytes (SPEs) have been widely studied due to its extensive applications in high energy rechargeable batteries, supercapacitors, fuel cells, photoelectrochemical and electrochromic displays. Herein, SPEs based on polyvinyl pyrrolidone (PVP) doped with cesium aluminate (CsAlO2) nanoparticles (NPs), lithium perchlorate (LiClO4) as an electrolyte and varying amounts viz., 2, 4, 6 and 8 wt.% of ethylene carbonate (EC) as plasticizer have been fabricated by solution intercalation technique. The structural features of PVP-CsAlO2-LiClO4-EC SPEs have been studied by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The morphology of PVP-CsAlO2-LiClO4-EC SPEs has been examined by scanning electron microscopy (SEM). The thermal properties of the SPEs were characterized by the thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC) techniques. The TGA and DSC results revealed that a significant reduction in thermal stability and glass transition temperature (Tg) of PVP with an increase in EC content in SPE films. The optoelectrical properties of PVP-CsAlO2-LiClO4-EC SPE films have been evaluated using UV–visible spectroscopy. The band gap energy (Eg) was found to decrease with an increase in EC content, exhibiting a minimum of 4.23 eV for PVP-8 wt.% CsAlO2-15 wt.% LiClO4-8 wt.% EC. This could be ascribed to the formation of localized states and increased degree of disorder in the PVP-CsAlO2-LiClO4 SPE films. The integrated plasticizers increase the values of refractive index (RI), optical conductivity, and dielectric constants of PVP-CsAlO2-LiClO4 SPE films. The AC conductivity of the SPEs has been evaluated at room temperature using digital LCR meter in the frequency range 100 Hz – 5 MHz. The conductivity strongly depends on CsAlO2 NPs and EC plasticizer content in SPEs.

Coating-Dependent Effects of Silver Nanoparticles on Tobacco Seed Germination and Early Growth.

Silver nanoparticles (AgNPs) are used in a wide range of consumer products because of their excellent antimicrobial properties. AgNPs released into the environment are prone to transformations such as aggregation, oxidation, or dissolution so they are often stabilised by coatings that affect their physico-chemical properties and change their effect on living organisms. In this study we investigated the stability of polyvinylpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB) coated AgNPs in an exposure medium, as well as their effect on tobacco germination and early growth. AgNP-CTAB was found to be more stable in the solid Murashige and Skoog (MS) medium compared to AgNP-PVP. The uptake and accumulation of silver in seedlings was equally efficient after exposure to both types of AgNPs. However, AgNP-PVP induced only mild toxicity on seedlings growth, while AgNP-CTAB caused severe negative effects on all parameters, even compared to AgNO3. Moreover, CTAB coating itself exerted negative effects on growth. Cysteine addition generally alleviated AgNP-PVP-induced negative effects, while it failed to improve germination and growth parameters after exposure to AgNP-CTAB. These results suggest that the toxic effects of AgNP-PVP are mainly a consequence of release of Ag+ ions, while phytotoxicity of AgNP-CTAB can rather be ascribed to surface coating itself.

Preparation and characterization of polyvinylpyrrolidone/cobalt ferrite functionalized chitosan graphene oxide (CoFe2O4@CS@GO-PVP) nanocomposite

Abstract Cobalt ferrite functionalized chitosan graphene oxide (CoFe2O4@CS@GO) was inserted successfully in polyvinylpyrrolidone (PVP), and its distribution was distinguished through scanning electron microscope (SEM) analysis. Furthermore, the thermal and structural characterizations of the CoFe2O4@CS@GO-PVP nanocomposite were accomplished via the TGA, DSC, FT-IR, and XRD methods. The magnetic characterization of the synthesized nanocomposite was specified by vibrating sample magnetometer (VSM). Results demonstrated the improved thermal stability of pure PVP with the addition of CoFe2O4@CS@GO. The DSC analysis results also showed that the glass transition temperature of 158.9°C–164.8°C was obtained for the CoFe2O4@CS@GO-PVP nanocomposites. The FT-IR spectra indicated that an interaction occurred between CoFe2O4@CS@GO and PVP. Due to a good distribution of CoFe2O4@CS@GO in the PVP matrix, the strong interaction shown by the ~18 cm−1 red shift with good complexation of the carbonyl functional group of PVP with CoFe2O4@CS@GO was observed for the CoFe2O4@CS@GO-PVP (5% w/w) nanocomposite.

Synthesis of Cu nanoparticles by chemical reduction method

Abstract Cu nanoparticles (CuNPs) have been synthesized through an easy route by chemical reduction at room temperature. The Cu2+ ions were reduced and stabilized with sodium borohydride and polyvinylpyrrolidone, respectively. The effect of the variation of the reducing agent/precursor-salt (RA/PS) ratio on the size and morphology of the CuNPs was evaluated. The synthesized material was studied by ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The UV-Vis spectra showed a CuNPs plasmon peak at 569 nm and another peak belonging to Cu2O at 485 nm. XRD analysis showed the fcc-Cu phase with a small amount of fcc-Cu2O compound. SEM and TEM studies displayed that small semispherical CuNPs of approximately 7 nm were obtained at the RA/PS ratio of 2.6. The excess of polyvinylpyrrolidone stabilizer played an essential role in preventing CuNPs oxidation. On the other side, Cu2O polyhedral particles with larger sizes up to 150 nm were identified in the RA/PS ratio range of 2.0–1.84. In addition, Cu2O particles having star morphologies with quantum confinement at their tips were obtained at the RA/PS ratio of 1.66.

Effect of Silver Nanoparticles on Protein Composition of Rat Liver Microsomal Fraction.

We studied the effect of oral administration of metallic silver nanoparticles to rats on the proteome of the liver microsomal fraction. Nanoparticles (5-80 nm) were administered daily to growing Wistar male rats over 92 days. Controls received pure water. To control the effect of the carrier, the rats were administered aqueous solution of a stabilizer polyvinylpyrrolidone. The protein composition (proteome) of the liver microsomal fraction was analyzed by 2D-electrophoresis with identification of variable protein spots using the high-resolution nanoHPLC-MS/MS. Eight, 6, and 8 proteins absent in the control groups appeared in the microsomal fraction under the action of nanoparticles in doses of 0.1, 1, and 10 mg/kg body weight, among these, proteasome activator complex subunit 1 (Psme1 gene), and the heat shock protein HSP60 (Hspd1 gene) were reliably identified. The consumption of silver nanoparticles led to disappearance of protein of β2a tubulin chain (Tuba1b gene) from the microsomal fraction. The expression of catalase, present in the proteome of the liver microsomal fraction in animals of all groups was significantly decreased after consumption of silver nanoparticles in doses of 0.1 and 10 mg/kg. The observed changes in the proteome are considered as manifestations of hepatotoxicity of silver nanoparticles and can be related to the antagonistic effect of silver on the status of the essential trace element selenium.

Effect of stabilizing agents on the conductivity of Co@TiO[formula omitted] core–shell nanoparticles

The main focus of this work is to choose a stabilizer which plays a significant role in enhancing the conductivity of Co@TiO2 nanoparticles. Poly Vinyl Pyrrolidone (PVP) and zeroth generation triazolyl Glycodendrimer were the stabilizing agents whose activity on Co@TiO2 nanoparticles has been compared. As a semiconductor with extreme resistivity Co@TiO2 shows good conductivity due to the presence of cobalt at the core which was further improved by suitable stabilizing agent. Being less reactive when exposed to light, glycodendrimer lags behind PVP in the conductivity test results. The results obtained from impedance analysis, UV–Diffuse Reflectance Spectrograph and photoconductivity shows that the activity of PVP stabilizer is better than glycodendrimer. The structural analysis of the synthesized samples shows that the lattice strain experienced by PVP is less than that of glycodendrimer.

Synthesis of water-free PEDOT with polyvinylpyrrolidone stabilizer in organic dispersant system

Abstract Poly (3, 4-ethylenedioxythiophene): tosylate (PEDOT: Tos) is synthesized by chemical oxidative polymerization with polyvinylpyrrolidone (PVP) as stabilizer in organic solvent. The effects of different molecular weight and additive amount of PVP stabilizer, various volume ratios of propylene carbonate (PC) to ethanol in organic system, different oxidative agents and various polymerization temperature/time on as-prepared PEDOT dispersion are taken into consideration and investigated systematically. Fourier transform infrared spectroscopy (FT-IR), film-forming property and electrical conductivity are studied and compared among different reaction conditions. The optimal polymerization scenario is to prepare PEDOT particles with 2 wt.% PVP (M.w. = 58,000) stabilizer and Fe2(SO4)3 oxidant at 80 °C for 24 h in organic system of PC and ethanol (volume ratio = 1: 3). Optimal PEDOT with PVP possesses more homogeneous particle size, better particle-particle connectivity in film and higher electrical conductivity (1.67*10−2 s cm−1) than that of PEDOT without PVP (5.2*10−4 s cm−1) and commercial organic PEDOT (4.7*10−4 s cm−1). The morphology and elemental composition of PEDOT particles with PVP are also investigated and compared with that of commercial organic PEDOT and aqueous PEDOT/PSS dispersion.

Compositional Optimization of Alloy FexNiy(OH)2 Nanoparticles for Alkaline Electrochemical Oxygen Evolution

Alloy FeNi nanoparticles were synthesized and evaluated as electrocatalysts for the oxygen evolution reaction in alkaline electrolyte. Electron microscopy imaging indicates nanoparticles were formed with a spherical morphology, and initial elemental analysis suggests significant oxygen content in the bimetallic particles. A molar ratio range from 5:1 to 1:5 Fe:Ni in the as-synthesized nanoparticles was tested. The effect of polyvinylpyrrolidone stabilizer on nanoparticle performance was also evaluated. Catalytic performance of the nanoparticles increased with decreasing Fe:Ni molar ratio and PVP:Ni molar ratio. Alloy nanoparticles synthesized with a Fe:Ni ratio of 1:5 and a PVP:Ni ratio of 0.001 resulted in an overpotential of 295 mV at 10 mA/cm2, a Tafel slope of 40 mV/dec, and a mass-based activity of 3343 mA/mg at 1.6 V vs. RHE.

Self-organization of nickel nanoparticles dispersed in acetone: From separate nanoparticles to three-dimensional superstructures

Sonochemical synthesis of monodisperse nickel nanoparticles (Ni-NPs) by reduction of Ni acetylacetonate in the presence of polyvinylpyrrolidone stabilizer is reported. The Ni-NPs size is readily controlled to 5 nanometer diameter with a standard deviation of less than 5%. The as-prepared Ni-NPs sample was dispersed in acetone, for 4weeks. For structural analysis was not applied to a magnetic field or heat treatment as key methods to direct the assembly. The transition from separate Ni-NPs into self-organization of three dimensions (3D) superstructures was studied by electron microscopy. Experimental analysis suggests that the translation and rotation movement of the Ni-NPs are governed by magnetic frustration which promotes the formation of different geometric arrangements in two dimensions (2D). The formation of 3D superstructures is confirmed from scanning electron microscopy revealing a layered domain that consists of staking of several monolayers having multiple well-defined supercrystalline domains, enabling their use for optical, electronic and sensor applications.

Influence of orally introduced silver nanoparticles on content of essential and toxic trace elements in organism

Nanoscale colloidal silver (NCS) is one of the most popular products of nanotechnology and is widely used in cosmetics, food supplements, and other types of consumer products. The aim of this work is to study the influence of NCSs orally introduced into rats during an experiment lasting 92 days on some indicators of homeostasis of essential and toxic trace elements. The Argovit-C NCSs produced by Vector Vita LTD, Novosibirsk, Russia with silver (Ag) nanoparticles of the diameter in the range of 5-80 nm according to transmission electron microscopy and dynamic laser light scattering. The drug is introduced into growing male Wistar rats in doses ranging from 0.1 to 10 mg/kg body weight (b.w.) for 1 month by gavage and then with a diet consumed for 62 days. The control animals receive deionized water or an aqueous solution of the stabilizer polyvinylpyrrolidone. The content of Ag, cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) in the liver, kidneys, and spleen is determined by mass spectrometry with inductively coupled plasma; selenium (Se) in serum and urine is measured by spectrofluorimetric method and glutathione peroxidase activity by the enzymatic spectrophotometric method. The dose-dependent accumulation of Ag in the animal liver at a dosage ranging 0.1–10 mg/kg b.w. and kidney and spleen in the range of 0.1–1 mg/kg b.w. is revealed. A significant decrease in the content of Cu in the kidneys; a decrease in Zn and Co content and increase in Mn content in the liver; and an increase in Cd, Cr, and Ni in spleen of animals receiving NCS at various doses are found. A significant positive correlation is found between the levels of Ag and Cd, Ni, Cr in the spleen, and a negative one is found between Ag and Cu in the kidneys. Indicators of Se provision (urinary excretion, the content in the blood plasma, the activity of glutathione peroxidase) are significantly lower in rats receiving NCS at a dose of 1.0–10 mg/kg b.w. Thus, NCSs, entering the body through the gastrointestinal tract at a dose of silver of at least 1 mg/kg b.w. may affect the homeostasis of essential and toxic trace elements. The antagonism of Ag (as part of the NCS) and Se in the composition of the diet should be taken into account in assessing the safety of widely used food supplements–sources of colloidal Ag.

A Simple Investigation of the Thermal Effusivity of Silver Nanofluid Using Photopyroelectric Technique

We investigated the thermal effusivity of silver nanofluids using a microwave technique. During microwave irradiation, silver nanoparticles with a narrow particle size distribution were formed in water and in ethylene glycol, with a polyvinylpyrrolidone stabilizer. We designed and used a front-photopyroelectric technique that employed a metalized polyvinylidene difluoride (PVDF) pyroelectric sensor, with a thermally thick sensor and sample. Using this technique, we calculated the thermal effusivity of the silver nanofluids at a given frequency using the combination of the signal’s normalized amplitude–phase. The thermal effusivity of the nanofluids increased with the number of microwave irradiation cycles, which increased the nanoparticle concentration in the base fluids. A comparison with reported values illustrates the high accuracy obtained from the results of thermal diffusivity, the thermal effusivity of the PVDF sensor, and the thermal effusivity of ethylene glycol as a base fluid (differing by only 1.7 %, 0.5 %, and 2.3 %, respectively). Our method can therefore be used to study nanofluids with varying nanoparticle properties, such as concentration, size, and shape.

One‐pot synthesis of self‐stabilized and carboxyl‐functionalized fluorescent poly(methyl methacrylate) microspheres covalently dyed with tris(8‐hydroquinolinato)aluminium by dispersion polymerization

AbstractThe dispersion polymerization of methyl methacrylate (MMA) with fluorescent monomer tris[2‐((8‐hydroxyquinolin‐5‐yl)methoxy)ethyl methacrylate]aluminium (Al‐HQHEMA) was investigated to obtain fluorescent microspheres under varying conditions (such as composition of dispersion medium, and content of stabilizer polyvinylpyrrolidone (PVP) and Al‐HQHEMA) in methanol–water at 70 °C with 2,2′‐azoisobutyronitrile as the initiator. Fluorescent microspheres with particle size of 2.039 µm and uniformity of 0.171 were obtained under the following conditions: methanol–water, 7:3 (v/v); PVP, 15 wt% of MMA; Al‐HQHEMA solution, 1.5 mL. Maleic monoester of monomethoxyl poly(ethylene glycol) (Mal‐MPEG) was used as a comonomer to simultaneously incorporate carboxyl groups and PEG chains. With Mal‐MPEG, no aggregation was observed in the measurements of particle size and size distribution for the obtained microspheres after cleaning off PVP, indicating that self‐stabilized fluorescent microspheres were obtained. While without Mal‐MPEG, obvious aggregation was observed. The determination of surface carboxyl content using aqueous acid–base titration showed that most of the carboxyl groups of Mal‐MPEG were located on the surface of the microspheres. © 2015 Society of Chemical Industry