ICP-MS: a powerful technique for quantitative determination of gold nanoparticles without previous dissolving

A direct and simple inductively coupled plasma mass spectroscopy (ICP-MS) method for the determination of gold nanoparticles (AuNP) with different particle sizes ranging from 5 to 20 nm and suspended in aqueous solutions is described. The results show no significant difference compared to the determination of the same AuNPs after digestion, as claimed by the literature. The obtained limit of quantification of the method is 0.15 μg/L Au(III) that corresponds to 4.40 × 10⁹ AuNP/L, considering spherical AuNPs 15 nm sized. Spike recovery experiments have shown that the sample matrix is a significant factor influencing the accuracy of the measurement. Spike recoveries from 93% to 95% are found for AuNP samples prepared in trisodium citrate, while for deionized H₂O a spike recovery of around 80% was obtained. The sample preparation mode along with the ICP-MS parameters have been optimized and found to be crucial so as to achieve the required accuracy for the direct quantification of AuNP suspensions. The effect of the nanoparticle size upon the ICP-MS signal also was studied, and only significant differences due to the chemical environment and not to the AuNPs size were found.     

Fabrication and electrochemical property modification of mixed matrix heterogeneous cation exchange membranes filled with Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/PAA core-shell nanoparticles

In the current research, iron oxide nanoparticles were functionalized by acrylic acid polymerization. The Fe₃O₄/PAA core-shell nanoparticles were utilized for the modification of cation exchange membranes. Ion exchange membranes were prepared by solution casting technique using cation exchange resin powder as functional group agent and tetrahydrofuran as solvent. FTIR analysis proved the formation of PAA on nanoparticles. The SOM images also showed uniform particle distribution for the prepared membrane relatively. The membrane water content was declined from 30 to 17 % by increase of nanoparticle content ratio in membrane matrix. The contact angle measurements showed that membrane surface hydrophilicity was improved by utilizing of nanoparticles in the membrane matrix. The membrane potential, permselectivity, and transport number were improved initially by increase of nanoparticle concentration in the casting solution and then began to decrease by more additive concentration. Membrane ionic flux and permeability were enhanced initially by increase of nanoparticle loading ratio up to 0.5 %wt in membrane matrix and then showed decreasing trend by more increase of nanoparticle concentration from 0.5 to 4 %wt. Membrane areal electrical resistance was decreased sharply by utilization of nanoparticles up to 0.5 %wt in membrane matrix then began to increase by more additive concentration. The prepared membranes exhibited superior selectivity and low ionic flux at neutral condition compared to other acidic and alkaline environments.     

Rapid preparation and characterization of chitosan nanoparticles for oligonucleotide

Chitosan is regarded as one of the potential candidates as a gene carrier. However, the poor solubility of chitosan is the major limiting factor in its utilization as a gene carrier. The purpose of this study was to simplify the method of preparing the nanoparticles of chitosan linked with antisense oligonucleotide (asON). The main step was preparing the derivatives of chitosan phosphate (CSP) in order to easily dissolve in aqueous solution. The nanoparticles were formed using a simple mixed method for CSP and asON, and the nanoparticle’s forming condition was optimized so that the nanoparticle’s characterization could be examined. Results showed that it was simple to make the nanoparticles under the optimal condition of 2:1 M proportion of CSP and asON. The size of the nanoparticles was 102.6 ± 12.0 nm, its zeta potential was 1.45 ± 1.75, and the encapsulated ratio of the chitosan crosslinked the asON was 87.6 ± 3.5%. The infrared spectra and electron microscope displayed that chitosan may combine with the asON to form equirotal nanoparticles. In conclusion, it was simple and feasible to form chitosan nanoparticles for asON using the CSP, and the CSP can efficiently encapsulate asON.     

Gelatin–Chitosan composite capped gold nanoparticles: a matrix for the growth of hydroxyapatite

Growth of hydroxyapatite (HA) on gelatin–chitosan composite capped gold nanoparticles is presented for the first time by employing wet precipitation methods and we obtained good yields of HA. Fourier transform infrared spectroscopy (FTIR) spectrum has shown the characteristic bands of phosphate groups in the HA. Scanning electron microscopy (SEM) pictures have shown spherical nanoparticles with the size in the range of 70–250 nm, whereas ≥2–50 nm sized particles were visualized in high resolution transmission electron microscopy (HR-TEM). X-ray diffraction (XRD) spectrum has shown Bragg reflections which are comparable with the HA. Energy dispersive X-ray (EDX) studies have confirmed calcium/phosphate stoichiometric ratio of HA. The thermogravimetric analysis (TGA) has shown about 74% of inorganic crystals in the nanocomposite formed. These results have revealed that gelatin–chitosan capped gold nanoparticles, acted as a matrix for the growth of HA.     

A stable ‘sandwich’ system of Surface‐Enhanced Resonance Raman Scattering for the analysis of β‐carotenes in a photosynthetic pigment‐protein complex

In plants, Photosystem I (PSI) is composed of a core complex and a membrane‐associated antenna complex light‐harvesting complex I that captures light and funnels its energy to the core complex. To obtain Raman structural information on β‐carotenes embedded in the PSI core complex, a ‘sandwich’ system of roughened silver slice: target protein complexes: single silver nanoparticles was fabricated for Surface‐Enhanced Resonance Raman Scattering (SERRS) measurements. This study provided a method to overcome spectral irreproducibility, which is the main drawback of Surface‐Enhanced Raman Scattering/SERRS‐based studies. The Raman spectra of β‐carotenes embedded in the PSI core complex can be obtained at very low sample concentrations (1–5 µg Chl/ml) and high signal/noise ratios. The β‐carotenes in the spinach PSI core complex were predominantly all‐trans configuration. The membrane protein‐mediated adsorption of silver nanoparticles induced the uniform distribution of a large number of single nanoparticles, which contributed to achieving highly reproducible SERRS spectra. This study is the first to apply single silver nanoparticle‐based SERRS analysis in membrane proteins. Copyright © 2013 John Wiley & Sons, Ltd.     

Controlled release of ketorolac through nanocomposite films of hydrogel and LDH nanoparticles

A novel nanocomposite film for sustained release of anionic ophthalmic drugs through a double-control process has been examined in this study. The film, made as a drug-loaded contact lens, consists principally of a polymer hydrogel of 2-hydroxyethyl methacrylate (HEMA), in whose matrix MgAl-layered double hydroxide (MgAl-LDH) nanoparticles intercalated with the anionic drug are well dispersed. Such nanocomposite films (hydrogel-LDH-drug) contained 0.6–0.8 mg of MgAl-LDH and 0.08–0.09 mg of the ophthalmic drug (ketorolac) in 1.0 g of hydrogel. MgAl-drug-LDH nanoparticles were prepared with the hydrodynamic particle size of 40–200 nm. TEM images show that these nanoparticles are evenly dispersed in the hydrogel matrix. In vitro release tests of hydrogel-LDH-drug in pH 7.4 PBS solution at 32 °C indicate a sustained release profile of the loaded drug for 1 week. The drug release undergoes a rapid initial burst and then a monotonically decreasing rate up to 168 h. The initial burst release is determined by the film thickness and the polymerization conditions, but the following release rate is very similar, with the effective diffusion coefficient being nearly constant (3.0 × 10⁻¹² m²/s). The drug release from the films is mechanistically attributed to anionic exchange and the subsequent diffusion in the hydrogel matrix.     

In-situ bioconjugation in stationary media and in liquid flow by femtosecond laser ablation

In-situ functionalization of gold nanoparticles with fluorophore-tagged oligonucleotides is studied by comparing femtosecond laser ablation in stationary liquid and in biomolecule flow. Femtosecond laser pulses induce significant degradation to sensitive biomolecules when ablating gold in a stationary solution of oligonucleotides. Contrary, in-situ conjugation of nanoparticles in biomolecule flow considerably reduces the degree of degradation studied by gel electrophoresis and UV–Vis spectrometry. Ablating gold with 100 μJ femtosecond laser pulses DNA sequence does not degrade, while the degree of fluorophore tag degradation was 84% in stationary solution compared to 5% for 1 mL/min liquid flow. It is concluded that femtosecond laser-induced degradation of biomolecules is triggered by absorption of nanoparticle conjugates suspended in the colloid and not by ablation of the target. Quenching of nanoparticle size appears from 0.5 μM biomolecule concentration for 0.3 μg/s nanoparticle productivity indicating the successful surface functionalization. Finally, increasing the liquid flow rate from stationary to 450 mL/min enhances nanoparticle productivity from 0.2 μg/s to 1.5 μg/s, as increasing liquid flow allows removal of light absorbing nanoparticles from the ablation zone, avoiding attenuation of subsequent laser photons.     

Poly ethylene oxide (PEO)–LiI polymer electrolytes embedded with CdO nanoparticles

Improvement of electrical conductivity of poly ethylene oxide (PEO)–LiI polymer electrolytes is necessary for their use in solid state lithium ion battery. In this study a new kind of PEO–LiI-based polymer electrolytes embedded with CdO nanoparticles with improved electrical conductivity has been prepared and characterized. The electron microscopic studies confirm that CdO nanoparticles of average size 2.5 nm are dispersed in the PEO matrix. The glass transition temperature of the PEO–LiI electrolyte decreases with the introduction of CdO nanoparticle in the polymer matrix. X-ray diffraction, electron microscopic, and differential scanning calorimetry studies show that the amorphous phase of PEO increases with the introduction of CdO nanoparticle and that the increase in amorphous phase is maximum for 0.10 wt% CdO doping. The electrical conductivity of the sample with 0.10 wt% CdO increases by three orders in magnitude than that of the PEO–LiI electrolyte. The electrical conductivity of PEO–LiI electrolyte embedded with CdO nanoparticle exhibits VTF behavior with reciprocal temperature indicating a strong coupling between the ionic and the polymer chain segmental motions.     

Evaluation of the sonosensitizing properties of nano-graphene oxide in comparison with iron oxide and gold nanoparticles

In cancer hyperthermia, ultrasound is considered as an appropriate source of energy to achieve desired therapeutic levels of heating. It is assumed that such a heating is targeted to cancer cells by using nanoparticles as sonosensitization agents. Here, we report the sonosensitizing effects of Nano-Graphene Oxide (NGO) and compare them with gold nanoparticles (AuNPs), Iron Oxide nanoparticles (IONPs).Experiments were conducted to explore the effects of nanoparticle type and concentration, as well as ultrasound power, on transient heating up of the solutions exposed by 1 MHz ultrasound. Nanoparticles concentration was selected from 0.25 to 2.5 mg/ml and the solutions were exposed by ultrasound powers from 1 to 8 W. Real time temperature monitoring was done by a thermocouple and obtained data was analyzed.Temperature profiles of various nanoparticle solutions showed the higher heating rates, in comparison to water. Heating rise was strongly depended on nanoparticles concentration and ultrasound power. AuNPs showed a superior efficiency in heat generation enhancement in comparison to IONPs and NGO.Our result supports the idea of sonosensitizing capabilities of AuNPs, IONPs, and NGO. Targeted hyperthermia may be achievable by preferential loading of tumor with nanoparticles and subsequent ultrasound irradiation.     

A newly developed Fe-doped calcium sulfide nanoparticles with magnetic property for cancer hyperthermia

In this study, a magnetic iron-doped calcium sulfide (Fe–CaS) nanoparticle was newly developed and studied for the purpose of hyperthermia due to its promising magnetic property, adequate biodegradation rate, and relatively good biocompatibility. Fe–CaS nanoparticles were synthesized by a wet chemical co-precipitation process with heat treatment in a N₂ atmosphere, and were subsequently cooled in N₂ and exposed to air at a low temperature. The crystal structure of the Fe–CaS nanoparticles was similar to that of the CaS, which was identified by an X-ray diffractometer (XRD). The particle size was less than 40 nm based on a Debye–Scherrer equation and transmission electron microscope (TEM) examination. Magnetic properties obtained from the SQUID magnetometer demonstrated that the synthesized CaS was a diamagnetic property. Once the Fe ions were doped, the synthesized Fe–CaS converted into paramagnetism which showed no hysteresis loop. Having been heated above 600 °C in N₂, the Fe–CaS showed a promising magnetic property to produce enough energy to increase the temperature for hyperthermia. 10 mg/ml of the Fe–CaS was able to generate heat to elevate the media temperature over 42.5 °C within 6 min. The area of the hysteresis loop increased with the increasing of the treated temperature, especially at 800 °C for 1 h. This is because more Fe ions replaced Ca ions in the lattice at the higher heat treatment temperature. The heat production was also increasing with the increasing of heat treatment temperature, which resulted in an adequate specific absorption ratio (SAR) value, which was found to be 45.47 W/g at 37 °C under an alternative magnetic field of f = 750 KHz, H = 10 Oe. The in vitro biocompatibility test of the synthesized Fe–CaS nanoparticles examined by the LDH assay showed no cytotoxicity to 3T3 fibroblast. The result of in vitro cell hyperthermia shows that under magnetic field the Fe–CaS nanoparticles were able to generate heat and kill the CT-26 cancer cells significantly. We believe that the developed Fe–CaS nanoparticles have great potential as thermo-seeds for cancer hyperthermia in the near future.     

Study of continuous flow ultrasonication to improve total phenolic content and antioxidant activity in sorghum flour and its comparison with batch ultrasonication

Ultrasonic technology was applied to release the phenolics bound with starch and protein matrix in order to enhance total phenolic content (TPC) and antioxidant activity (AA) of the sorghum flour. Both the continuous flow and batch ultrasonication were implied with independent variables such as flour to water ratio (FWR), ultrasonication intensity (UI), and ultrasonication time (UT) with an additional variable as flow rate (FR) in continuous flow ultrasonication. All the process variables showed a significant effect on the corresponding ultrasonication process. The optimal conditions for the continuous flow ultrasonication were a FWR of 10% w/v, an UI of 20 W/cm², an UT of 130 s, and 15 ml/s FR which produced a maximum values of 70.9 mg GAE/100 g dry matter (d.m.) for TPC and 143.9 µmol TE/100 g d.m. for AA. Regarding the batch ultrasonication, the maximum values were 65.6 mg GAE/100 g d.m. and 141.0 µmol TE/100 g d.m. for TPC and AA, respectively at optimum conditions of 10% w/v FWR, 30 W/cm² UI, and 200 s UT. When comparing with the batch ultrasonication, the continuous flow process saved 35% time and 33% of energy consumption to obtain comparatively higher TPC and AA of the sorghum flour. Ultrasonication improved free phenolic acid content by releasing bound phenolics in the sorghum flour. Impact of various process parameters on specific energy was analyzed during both the processes, and influence of energy on TPC and AA of the sorghum flour was also observed for the batch and continuous flow ultrasonication.     

Systematic evaluation of biocompatibility of magnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles with six different mammalian cell lines

This article systematically evaluated the biocompatibility of multiple mammalian cell lines to 11-nm DMSA-coated Fe₃O₄ magnetic nanoparticles (MNPs). Cells including RAW264.7, THP-1, Hepa1-6, HepG2, HL-7702, and HeLa were incubated with six different concentrations (0, 20, 30, 40, 50, and 100 μg/mL) of MNPs for 48 h, and then the cell labeling, iron loading, cell viability, apoptosis, cycle, and oxidative stress were all quantitatively evaluated. The results revealed that all the cells were effectively labeled by the nanoparticles; however, the iron loading of RAW264.7 was significantly higher than that of other cells at any dose. The proliferations of all the cells were not significantly suppressed by MNPs at the studied dose except HepG2 that was exposed to 100 μg/mL MNPs. The investigation of oxidative stress demonstrated that the levels of total superoxide dismutase and xanthine oxidase had no significant changes in all the cells treated by all the doses of MNPs, while the levels of malonyldialdehyde activity of MNP-treated cells significantly increased. The nanoparticles did not produce any significant effect on cell cycles at any of the doses, but resulted in significant apoptosis of THP-1 and HepG2 cells at the highest concentration of 100 μg/mL. At a concentration of 30 μg/mL which was used in human studies with an intravascular nanoparticle imaging agent (Combidex), the nanoparticles efficiently labeled all the cells studied, but did not produce any significant influence on their viability, oxidative stress, and apoptosis and cycle. Therefore, the nanoparticles were concluded with better biocompatibility, which provided some useful information for its clinical applications.     

Effects of iron oxide nanoparticles on polyvinyl alcohol: interfacial layer and bulk nanocomposites thin film

Iron oxide (α-phase) nanoparticles with coercivity larger than 300 Oe have been fabricated at a mild temperature by an environmentally benign method. The economic sodium chloride has been found to effectively serve as a solid spacer to disperse the iron precursor and to prevent the nanoparticles from agglomeration. Higher ratios of sodium chloride to iron nitrate result in smaller nanoparticles (19 nm for 20:1 and 14 nm for 50:1). The presence of polyvinyl alcohol (PVA) limits the particle growth (15 nm for 20:1 and 13 nm for 50:1) and favors nanoparticle dispersion in polymer matrices. Obvious physicochemical property changes have been observed with PVA attached to the nanoparticle surface. With PVA attached to the nanoparticle surface, the nanoparticles are found not only to increase the PVA cross-linking with an increase in melting temperature but also to enhance the thermal stability of the PVA. The nanoparticles are observed to be uniformly dispersed in the polymer matrix. Scanning electron microscopy (SEM) microstructure also shows an intermediate phase with a strong interaction between the nanoparticles and the polymer matrices, arising from the hydrogen bonding between the PVA and hydroxyl groups on the nanoparticle surface. The addition of nanoparticles favors the cross-linkage of the bulk PVA matrices, resulting in a higher melting temperature, and an enhanced thermal stability of the polymer matrix.     

Synthesis of transparent BaTiO3 nanoparticle/polymer composite film using DC field

Transparent BaTiO₃ nanoparticle/polymer composite films were synthesized from titanium-organic film and barium ion in aqueous solution under direct current (DC) field. Titanium-organic precursor was synthesized from titanium isopropoxide, acetylacetone and methacrylate derivative. The UV treatment was effective to increase the anti-solubility of the titanium-organic film during DC processing. BaTiO₃ nanoparticles were crystallized in the precursor films on stainless substrates without high temperature process, as low as 40°C. The crystallite size of BaTiO₃ increased with increasing reaction temperature from 40 to 50 °C at 3.0 V/cm. BaTiO₃ nanoparticles also grew in size with increasing reaction time from 15 min to 45 min at 3.0 V/cm and 50 °C. Transparent BaTiO₃ nanoparticle/polymer films were synthesized on stainless substrates at 3.0 V/cm and 50°C for 45 min.     

Experimental study of nanoparticles penetration through commercial filter media

In this study, nanoparticle penetration was measured with a wide range of filter media using silver nanoparticles from 3 nm to 20 nm at three different face velocities in order to define nanoparticle filtration characteristics of commercial fibrous filter media. The silver particles were generated by heating a pure silver powder source via an electric furnace with a temperature of 870°C, which was found to be the optimal temperature for generating an adequate amount of silver nanoparticles for the size range specified above. After size classification using a nano-DMA, the particle counts were measured by an Ultrafine Condensation Particle Counter (UCPC) both upstream and downstream of the test filter to determine the nanoparticle penetration for each specific particle size. Particle sampling time continued long enough to detect more than 10⁵ counts at the upstream and 10 counts at the downstream sampling point so that 99.99% efficiency can be detected with the high efficiency filter. The results show a very high uniformity with small error bars for all filter media tested in this study. The particle penetration decreases continuously down to 3 nm as expected from the classical filtration theory, and together with a companion modeling paper by␣Wang et al. in this same issue, we found no significant evidence of nanoparticle thermal rebound down to 3 nm.     

Electron paramagnetic resonance of sonicated powder suspensions in organic solvents

The chemical effects of the acoustic cavitation generated by ultrasound translates into the production of highly reactive radicals. Acoustic cavitation is widely explored in aqueous solutions but it remains poorly studied in organic liquids and in particular in liquid/solid media. However, several heterogeneous catalysis reactions take place in organic solvents.Thus, we sonicated trimethylene glycol and propylene glycol in the presence of silica particles (SiO₂) of different sizes (5–15 nm, 0.2–0.3 µm, 12–26 µm) and amounts (0.5 wt% and 3 wt%) at an ultrasound frequency of 20 kHz to quantify the radicals generated. The spin trap 5,5-dimethyl-1-pyrrolin–N-oxide (DMPO) was used to trap the generated radicals for study by electron paramagnetic resonance (EPR) spectroscopy. We identified the trapped radical as the hydroxyalkyl radical adduct of DMPO, and we quantified it using stable radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a quantitation standard. The concentration of DMPO spin adducts in solutions containing silica size 12–26 µm was higher than the solution without particles. The presence of these particles increased the concentration of the acoustically generated radicals by a factor of 1.5 (29 µM for 0.5 wt% of SiO₂ size 12–26 µm vs 19 µM for 0 wt%, after 60 min of sonication). Ultrasound produced fewest radicals in solutions with the smallest particles; the concentration of radical adducts was highest for SiO₂ particle size 12–26 µm at 0.5 wt% loading, reaching 29 µM after 60 min sonication. Ultrasound power of 50.6 W produced more radicals than 24.7 W (23 µM and 18 µM, respectively, at 30 min sonication). Increased temperature during sonication generated more radical adducts in the medium (26 µM at 75 °C and 18 µM at 61 °C after 30 min sonication). Acoustic cavitation, in the presence of silica, increased the production of radical species in the studied organic medium.     

Fabrication and characterization of iron oxide nanoparticles filled polypyrrole nanocomposites

The effect of iron oxide nanoparticle addition on the physicochemical properties of the polypyrrole (PPy) was investigated. In the presence of iron oxide nanoparticles, PPy was observed in the form of discrete nanoparticles, not the usual network structure. PPy showed crystalline structure in the nanocomposites and pure PPy formed without iron oxide nanoparticles. PPy exhibited amorphous structure and nanoparticles were completely etched away in the nanocomposites formed with mechanical stirring over a 7-h reaction. The thermal stability of the PPy in the nanocomposites was enhanced under the thermo-gravimetric analysis (TGA). The electrical conductivity of the nanocomposites increased greatly upon the initial addition (20 wt%) of iron oxide nanoparticles. However, a higher nanoparticle loading (50 wt%) decreased the conductivity as a result of the dominance of the insulating iron oxide nanoparticles. Standard four-probe measurements indicated a three-dimensional variable-range-hopping conductivity mechanism. The magnetic properties of the fabricated nanocomposites were dependent on the particle loading. Ultrasonic stirring was observed to have a favorable effect on the protection of iron oxide nanoparticles from dissolution in acid. A tight polymer structure surrounds the magnetic nanoparticles, as compared to a complete loss of the magnetic iron oxide nanoparticles during conventional mechanical stirring for the micron-sized iron oxide particles filled PPy composite fabrication.     

Gold nanorods surface modified with poly(acrylic acid) as a template for the synthesis of metallic nanoparticles

Poly(acrylic acid) (PAA) surface-modified gold nanorods, contained in deionized ultra filtered (DIUF) water, served as templates for the formation of gold (Au), palladium (Pd), and platinum (Pt) nanoparticles upon reduction with NaBH₄. This provided nanoparticles with respective diameters of 7.0 ± 0.7, 4.1 ± 0.4, and 5.1 ± 0.5 nm. Varying amounts of Pt metal salt were used in EG, which acts as both a solvent and a reducing agent, ranging from 0.1, 0.2, and 1.0 mg/mL, to provide control over nanoparticle diameters of 2.0 ± 0.5 nm, to 4.0 ± 0.5 nm, and 6.2 ± 1.9 nm, respectively. Nanoparticle diameter was also controlled in DIUF water by varying the amount of Pt metal salt from 0.1, 0.2, and 1.0 mg/mL, producing Pt particle diameters, respectively, increasing from 2.7 ± 0.3 nm to 4.1 ± 0.5 nm, and 6.0 ± 0.6 nm.     

Highly sensitive and selective detection of glutathione using ultrasonic aided synthesis of graphene quantum dots embedded over amine-functionalized silica nanoparticles

Glutathione (GSH) is the most abundant antioxidant in the majority of cells and tissues; and its use as a biomarker has been known for decades. In this study, a facile electrochemical method was developed for glutathione sensing using voltammetry and amperometry analyses. In this study, a novel glassy carbon electrode composed of graphene quantum dots (GQDs) embedded on amine-functionalized silica nanoparticles (SiNPs) was synthesized. GQDs embedded on amine-functionalized SiNPs were physical-chemically characterized by different techniques that included high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction spectroscopy (XRD), UV–visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy. The newly developed electrode exhibits a good response to glutathione with a wide linear range (0.5–7 µM) and a low detection limit (0.5 µM) with high sensitivity(2.64 µA µM⁻¹). The fabricated GQDs-SiNPs/GC electrode shows highly attractive electrocatalytic activity towards glutathione detection in the neutral media at low potential due to a synergistic surface effect caused by the incorporation of GQDs over SiNPs. It leads to higher surface area and conductivity, improving electron transfer and promoting redox reactions. Besides, it provides outstanding selectivity, reproducibility, long-term stability, and can be used in the presence of interferences typically found in real sample analysis.     

Enhanced transport of zerovalent iron nanoparticles in saturated porous media by guar gum

In order to ensure adequate mobility of zerovalent iron nanoparticles in natural aquifers, the use of a stabilizing agent is necessary. Polymers adsorbed on the nanoparticle surface will give rise to electrosteric stabilization and will decrease attachment to the surface soil grains. Water saturated sand-packed columns were used in this study to investigate the transport of iron nanoparticle suspensions, bare or modified with the green polymer guar gum. The suspensions were prepared at 154 mg/L particle concentration and 0.5 g/L polymer concentration. Transport experiments were conducted by varying the ionic strength, ionic composition, and approach velocity of the fluid. Nanoparticle deposition rates, attachment efficiencies, and travel distances were subsequently calculated based on the classical particle filtration theory. It was found that bare iron nanoparticles are basically immobile in sandy porous media. In contrast, guar gum is able to ensure significant nanoparticle transport at the tested conditions, regardless of the chemistry of the solution. Attachment efficiency values for guar gum-coated nanoparticles under the various conditions tested were smaller than 0.066. Although the calculated travel distances may not prove satisfactory for field application, the investigation attested the promising role of guar gum to ensure mobility of iron nanoparticles in the subsurface environment.