Surface Area Of Nanoparticles Research Articles

CeO2 NANOTANECİKLERİNİN SENTEZİ, KARAKTERİZASYONU VE FOTOKATALİTİK AKTİVİTESİ

The discharge of untreated wastewater from unplanned industrial activities using dyes can cause serious environmental pollution and affect the aquatic environment. Semiconductor photocatalysis is a favorable technology widely used for degrading organic dyes in wastewater. This study dealt with the preparation of CeO2 nanoparticles via a simple precipitation technique. Information on the structural and morphological features of the developed CeO2 nanoparticles were determined using Fourier transform infrared with attenuated total reflectance (FTIR-ATR), Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) spectroscopic methods. The presence of the characteristic bands of CeO2 in the FTIR spectrum provided evidence of successful CeO2 formation. The calculated crystallite particle size utilizing the Scherrer equation was 10 nm. SEM images revealed that the morphology of CeO2 consisted of almost spherical particles with slight agglomeration. Brunauer-Emmett-Teller (BET) technique was also used to find out the specific surface area of CeO2 nanoparticles (11 m2/g). The efficiency of CeO2 nanoparticles was also confirmed in terms of their photocatalytic activity against Rhodamine B (Rh B) under UV-A light. The results indicated that CeO2 nanoparticles could be a promising catalyst candidate for industrial wastewater treatment.

Activation of peroxymonosulfate using heterogeneous Fe-doped carbon-based catalyst to generate singlet oxygen for the degradation of sulfamethoxazole

Non-radical catalytic oxidation processes can eliminate refractory pollutants from wastewater containing complex substrates such as dissolved organic matter, but the production of selective non-radicals is challenging during the activation of peroxymonosulfate (PMS). Herein, a novel magnetic carbon-based catalyst (Fe3O4@CD-8, where 8 represents an annealing temperature of 800 ℃) with N and Fe species as catalytic active sites was fabricated to remediate sulfamethoxazole (SMX)-containing water. It showed excellent SMX removal efficiency and facilitated singlet oxygen (1O2) production. The characterization results revealed that Fe3O4@CD-8 had a microscopically hierarchical pore structure and an overall core–shell-like structure. Due to its large specific surface area, N-containing species, and Fe nanoparticles, 0.1 g/L Fe3O4@CD-8 removed almost 100% SMX (24 min) and achieved a 44.1% mineralization (40 min) efficiency in the presence of 0.5 mM PMS. This catalytic system also maintained its removal performance in the presence of inorganic anions and humic acids and over a wide pH range of 3–11, showing good tolerance to various environmental factors. 1O2 was confirmed to be the predominant active species for SMX degradation using the Fe3O4@CD-8/PMS system. Density functional theory (DFT) calculations, intermediate monitoring, and toxicity evaluation demonstrated that SMX was transformed into low-toxicity molecules and completely mineralized into CO2 and H2O. The addition of Fe nanoparticles enhanced PMS adsorption and facilitated the Fe(III)/Fe(II) redox cycle to accelerate the activation of PMS. This study provides new insights and strategies for the controlled production of non-radicals for remediating antibiotic-containing wastewater.

Magnetic Nanocomposites for Removal of Arsenic from Water

Arsenic significantly impacts human health and the environment and its removal from wastewater is still difficult. Magnetic nanoparticles have come to light as a viable arsenic remediation technique, providing a fresh and long-lasting water purification method. This study investigates the use of magnetic nanoparticles to remove arsenic by concentrating on their adsorption mechanism, kinetics, potential for adsorption, recovery, and promising use of this method in the future. Due to the extensive surface area and variable surface chemistry of magnetic nanoparticles, they can effectively adsorb arsenic from water sources. Because their magnetic properties simplify separation and regeneration, they may be used again with little to no efficiency loss. As a result, they reduce trash output by providing an ecologically acceptable alternative to traditional adsorbents. The present study also examines the kinetics and adsorption process of magnetic nanoparticles, emphasising their improved selectivity and capacity for adsorption. Due to these characteristics, the authors were able to successfully remove arsenic from wastewater, resulting in better water quality and decreased health hazards after exposure to arsenic. Additionally, the potential applications of magnetic nanoparticles in removing arsenic have been highlighted. It is envisaged that advances in material science and nanotechnology will create unique magnetic nanoparticles with even better performance. Combining hybrid materials and surface alterations can increase their effectiveness in wastewater treatment settings.

Nanoparticles loaded with β-Lapachone and Fe3+ exhibit enhanced chemodynamic therapy by producing H2O2 through cascaded amplification

The rapid, irreversible change of active Fe2+ to inactive Fe3+ after the Fenton reaction occurring reduces the chemodynamic therapeutic (CDT) effect. Therefore, manipulation of the tumor microenvironment to provide sufficient hydrogen peroxide (H2O2) while maintaining metal ion catalyst activity is critical for effective CDT. Here, β-Lapachone (LPC) was loaded by mesoporous silica nanoparticles (MSNs) and coated with polydopamine (PDA) to further chelate Fe3+ and link aptamer AS1411, and a pH-controlled released, chemotherapy-photothermal therapy (PTT)-enhanced CDT-small molecule therapy combination drug delivery system with passive and active tumor targeting was engineered (designated as β-LPC@MSN@PDA/Fe3+-AS1411, LMPFA). The results showed that LFMPA nanoparticles massively accumulated in tumor tissues to achieve tumor targeting through AS1411 mediating and enhanced permeability and retention (EPR) effect. Subsequently, PDA released Fe3+ and LPC through acid response to exhibited CDT and chemotherapeutic therapy. Meanwhile, the photothermal effect of PDA promoted the release of LPC from the pores of MSN. LPC exerted chemotherapy effect and cyclically producing of H2O2 by the catalysis of NQO1, which enhanced the CDT activated by Fe3+. In addition, while serving as a targeted ligand, AS1411 could also exhibit a small molecule therapeutic effect by binding to nucleoli of tumor cells. This unique nano delivery system achieved the combination of chemotherapy, PTT, enhanced CDT and small molecule therapy, and fought against malignant tumors synergistically through multi-target and multi-dimension.

Optically Imaging In Situ Effects of Electrochemical Cycling on Single Nanoparticle Electrocatalysis.

Single-nanoparticle studies often need one or a series of nanoparticle populations that are designed with differences in a nominally particular structural parameter to clarify the structure-activity relationship (SAR). However, the heterogeneity of various properties within any population would make it rather difficult to approach an ideal one-parameter control. In situ modification ensures the same nanoparticle to be investigated and also avoids complicating effects from the otherwise often needed ex situ operations. Herein, we apply electrochemical cycling to single platinum nanoparticles and optically examine their SAR. An electrocatalytic fluorescent microscopic method is established to evaluate the apparent catalytic activity of a number of single nanoparticles toward the oxygen reduction reaction. Meanwhile, dark-field microscopy with the substrate electrode under a cyclic potential control is found to be able to assess the electrochemically active surface area (ECSA) of single nanoparticles via induced chloride redox electrochemistry. Consequently, nanoparticles with drastically increased catalytic activity are discovered to have larger ECSAs upon potential regulation, and interestingly, there are also a few particles with decreased activity, as opposed to the overall trend, that all develop a smaller ECSA in the process. The deactivated nanoparticles against the overall enhancement effects of potential cycling are revealed for the first time. As such, the SAR of single nanoparticles when subjected to an in situ structural control is optically demonstrated.

PVA-TiO2 Nanocomposite Hydrogel as Immobilization Carrier for Gas-to-Liquid Wastewater Treatment

This study investigates the development of polyvinyl alcohol (PVA) gel matrices for biomass immobilization in wastewater treatment. The PVA hydrogels were prepared through a freezing–thawing (F-T) cross-linking process and reinforced with high surface area nanoparticles to improve their mechanical stability and porosity. The PVA/nanocomposite hydrogels were prepared using two different nanoparticle materials: iron oxide (Fe3O2) and titanium oxide (TiO2). The effects of the metal oxide nanoparticle type and content on the pore structure, hydrogel bonding, and mechanical and viscoelastic properties of the cross-linked hydrogel composites were investigated. The most durable PVA/nanoparticles matrix was then tested in the bioreactor for the biological treatment of wastewater. Morphological analysis showed that the reinforcement of PVA gel with Fe2O3 and TiO2 nanoparticles resulted in a compact nanocomposite hydrogel with regular pore distribution. The FTIR analysis highlighted the formation of bonds between nanoparticles and hydrogel, which caused more interaction within the polymeric matrix. Furthermore, the mechanical strength and Young’s modulus of the hydrogel composites were found to depend on the type and content of the nanoparticles. The most remarkable improvement in the mechanical strength of the PVA/nanoparticles composites was obtained by incorporating 0.1 wt% TiO2 and 1.0 wt% Fe2O3 nanoparticles. However, TiO2 showed more influence on the mechanical strength, with more than 900% improvement in Young’s modulus for TiO2-reinforced PVA hydrogel. Furthermore, incorporating TiO2 nanoparticles enhanced hydrogel stability but did not affect the biodegradation of organic pollutants in wastewater. These results suggest that the PVA-TiO2 hydrogel has the potential to be used as an effective carrier for biomass immobilization and wastewater treatment.

Synthesis of porous ZrC particles derived from MOF-801

Porous zirconium carbide (ZrC) nanoparticles were synthesized by carbothermal reduction using MOF-801, a zirconium-based metal-organic framework (Zr-MOF), and sucrose, which serves as an environment-friendly carbon source. The sucrose was adsorbed into the pores of MOF-801 for adjusting the carbon content. The results showed that the final ZrC particles retained the morphology of the initial MOF-801 particles with a round shape and a uniform size of 261 ± 37 nm. Importantly, the material was able to maintain its high surface area up to 1500 °C. The specific surface area of ZrC nanoparticles synthesized using a 1.5:1 Sucrose: MOF-801 molar ratio gradually decreased from 186 m2/g to 13 m2/g as the reaction temperature increased from 1500 °C to 2000 °C, revealing that the porosity of the porous ZrC particles can be controlled due to partial sintering inside the particles at different temperatures. Porous ZrC particles show promise for ultra-high temperature applications such as thermal insulation and as porous substrates.

Preparation of amino-functionalized polyethylene-silica composite membrane and FDH immobilization

Enzymatic CO2 conversion represents a highly efficient, energy-conserving, and environmentally sustainable approach to mitigating the increasing pressure caused by huge carbon emissions and generating valuable products. However, several challenges associate with the process including the instability and recovery difficulty of free enzyme, as well as low solubility of CO2 in mild conditions. Immobilizing enzyme on the amino-functionalized supports presents a viable solution to these issues. Considering the wide application of polymer hollow fiber membranes in the field of CO2 gas–liquid membrane contactor and the characteristics of hydrophilic, biocompatible, and high specific surface area of silica nanoparticles, the amino-functionalized polyethylene (PE)-silica (APS) composite membranes were fabricated via different routes. The morphologies, the loading rates of modified SiO2 and reusability of APS membranes were characterized for a crude screening. Following that, seven kinds of APS membranes were used as the carriers of formate dehydrogenase (FDH) that could catalyze the reduction of CO2 to formate, and their immobilization efficiency and catalytic performance were compared. The results show that 1# and 2# membranes based on carboxyl-modified PE with a loading rate of 5.5 %∼5.6 % and the reusability of above 99 % were more ideal carriers than others. The enzyme activity recovery rate of APS-immobilized FDH (FDH-APS) was separately 367 % and 256 %, proving the intensification action of carriers on the enzymatic reaction. After 10 cycles of use, the relative activity of two kinds of FDH-APS was around 70 % and 78 %, much higher than corresponding particles or membrane attached FDH (25.3 % and 20.4 %). After storage at 4 °C for 20 days, the relative activity of FDH-APS was 82.7 % and 81.0 %, while it was only 61.4 % for free enzyme.

Reactive mesoporous organosoluble multifunctional hyperbranched polymer nanoparticles: Synthesis, post-polymerization reactions and clickable layer-by-layer coating

Synthesis of reactive organosoluble porous polymers, which can be useful for covalent layer-by-layer coatings, is synthetically challenging and not well known. In this work, we demonstrated a new approach to synthesize indole-decorated mesoporous hyperbranched polymer nanoparticles, which can be easily post-modified via triazolinedione (TAD)-indole click reaction. Importantly, further crosslinking of the polymer nanoparticles in solution leads to formation of insoluble mesoporous polymers, where porosity and surface area of the hyperbranched polymer nanoparticles further improved by ∼40%. Consequently, the nanoparticles are useful in layer-by-layer porous coatings and post-surface modifications. While studying their water repellent properties it was noted that nanoparticles having higher surface area/porosity results better water repellent surface which can be further enhanced via suitable surface functionalization using different long chain alkyl functionalities.

Oxytetracycline degradation and antidermatophytic activity of novel biosynthesized MoS2 photocatalysts

The presence of environmental contamination poses a significant threat to life on our planet. Oxytetracycline, an antibiotic with a broad spectrum of effectiveness, demonstrates resistance to biodegradation, potentially resulting in an ecological hazard. In this study, we synthesized both pure and biosynthesized Molybdenum Disulfide (MoS2) nanoparticles using extracts from the bark of Ficusreligiosa L (FR) and leaves of ZiziphusjujubeL (ZJ). These nanopartices were characterized by various analytical methods to assess their efficiency in photocatalytic degradation of oxytetracycline (OTC) and their antidermatophytic activity. X-ray diffraction patterns revealed that the prepared MoS2 catalysts typically exhibited hexagonal phase structure with crystalline size of approximately 13, 6, and 4 nm. Both pure and biosynthesized MoS2 nanoparticles displayed a nanoflake-like morphology with a spherical size distribution. BET surface area analyses exhibited an increase in surface area for biosynthesized MoS2 nanoparticles from 79 to 121 m2g−1. Optical absorption revealed a red shift in band gap energy, decreasing from 2.37 to 2.03 eV for biosynthesized MoS2 nanoparticles. The biosynthesized MoS2:FR nanoparticles exhibited remarkable OTC degradation with 99 % achieved within 100 min along with strong antifungal activity (Minimum Inhibitory Concentration - MIC of 12.5 µg/mL, Minimum Fungicidal Concentration - MFC of 25 µg/mL). These biosynthesized MoS2 catalysts are promising for water treatment purposes.

Chitosan-assisted hydrogen adsorption and reversibility of Ni-doped hierarchical carbon scaffolds.

We investigated the effects of chitosan (CS) on the hydrogen adsorption and reversibility of hierarchical carbon scaffold (HCS) loaded with Ni nanoparticles. As size-controllable, stabilizing, and shape-directing agents for the green synthesis of metal nanoparticles of CS, Ni nanoparticles with uniform distribution and shape are deposited onto HCS. The latter results in the superior specific surface area of Ni nanoparticles for hydrogen chemisorption. The best hydrogen adsorption capacities at room temperature under 20-70 bar H2 of 0.5-1.70 wt% H2 were obtained from 10 wt% Ni-doped HCS-CS. Although macropores of the HCS collapsed upon cycling due to hydrogen pressure applied during adsorption, average hydrogen capacities of 1.17 ± 0.05 wt% H2 (T = 25 °C and p(H2) = 50 bar) were maintained for 14 cycles. This is because not only uniform distribution and shape of Ni nanoparticles and microporous structures of the HCS were preserved upon cycling but also the interactions between Ni and heteroatoms (N and O) of the HCS and CS prevented particle agglomeration.

Effect of calcination temperature of titanium dioxide (TiO2) on adsorption performance of doxycycline hydrochloride

In this work, titanium dioxide (TiO2) was synthesized at different calcination temperatures by sol-gel method using butyl titanate as raw material. The effect of calcination temperature on the crystallinity and adsorption properties of TiO2 were investigated at 300 °C, 450 °C and 600 °C, respectively. The characteristics of TiO2 were analysed by X-ray diffraction, field emission scanning electron microscopy, nitrogen adsorption-desorption analyzer and zeta potential tester. The results showed that the crystal type, specific surface area and zeta potential of TiO2 nanoparticles changed with the increase of calcination temperature and the best performance of anatase crystals happened at the calcination temperature of 300 °C (TiO2@300) for doxycycline hydrochloride (DCH) adsorption. The equilibrium adsorption capacities of DCH was 28.97 mg/g with DCH removal rate of 86.92% at 0.03 g TiO2@300 addition in 100 ml 10 mg/L DCH solution. TiO2@300 could be a promising adsorbent.

Enhanced photovoltaic performance of green synthesized Fe3O4 nanostructures embedded in TiO2 photoanode for dye sensitized solar cells

This study assessed the influence of incorporating green-synthesized Fe3O4 nanoparticle into TiO2 for enhanced photovoltaic performance of photoanode in DSSC. Iron (II, III) Oxide (Fe3O4) nanoparticle was successfully synthesized using Carica papaya leaves extract. Natural dyes were used as sensitizers along with commercially available Ruthenium dye (N719). The optical absorptions observed between 350 and 600 nm confirmed the formation of Fe3O4 nanoparticle. The XRD patterns showed the crystalline nature of the Fe3O4 nanoparticle with the average crystallite size of 12.16 nm. The morphologies of the samples demonstrated that the Fe3O4 nanoparticle was well-formed and homogeneously dispersed. The EDX spectral of the samples affirmed the presence of iron and other constituent elements. The TEM micrograph also confirmed the formation of nanoparticles with an average size of 13.55 nm and the SAED patterns revealed the crystallographic planes of the samples. The DSSCs performance showed that the efficiencies increased significantly with percentage increase of 75.8%, 80.0%, 92.8% and 89.3% for Vernonia amygdalina, Camellia sinensis, Indigofera tinctoria and Ruthenium dyes, respectively. The high specific surface area, biocompatibility and good dispersion of the green-synthesized Fe3O4 nanoparticle incorporated into the photoanode of DSSC suggested that it is a promising nanomaterial for application in DSSC.

Adsorption and photodegradation of organic contaminants by silver nanoparticles: isotherms, kinetics, and computational analysis.

In view of the widespread and distribution of several classes and types of organic contaminants, increased efforts are needed to reduce their spread and subsequent environmental contamination. Although several remediation approaches are available, adsorption and photodegradation technologies are presented in this review as one of the best options because of their environmental friendliness, cost-effectiveness, accessibility, less selectivity, and wider scope of applications among others. The bandgap, particle size, surface area, electrical properties, thermal stability, reusability, chemical stability, and other properties of silver nanoparticles (AgNPS) are highlighted to account for their suitability in adsorption and photocatalytic applications, concerning organic contaminants. Literatures have been reviewed on the application of various AgNPS as adsorbent and photocatalyst in the remediation of several classes of organic contaminants. Theories of adsorption have also been outlined while photocatalysis is seen to have adsorption as the initial mechanism. Challenges facing the application of silver nanoparticles have also been highlighted and possible solutions have been presented. However, current information is dominated by applications on dyes and the view of the authors supports the need to strengthen the usefulness of AgNPS in adsorption and photodegradation of more classes of organic contaminants, especially emerging contaminants. We also encourage the simultaneous applications of adsorption and photodegradation to completely convert toxic wastes to harmless forms.

Successful synthesis of LaFeO3 nanoporous powders with high catalytic and photocatalytic performances: Investigation of precursor effect

Porous LaFeO3 powders with high catalytic and photocatalytic activities were successfully synthesized by sol-gel method using nitrate and chloride precursors. The precursor effect on the crystal structure, morphology, specific surface area and optical properties of the prepared powders was fully determined. Thermogravimetric and X-ray diffraction analyzes showed the formation of the orthorhombic perovskite phase (Pnma, #62) at annealing temperature of 800 and 1000 °C for powder prepared by nitride and chloride salts, respectively. The scanning electron microscopy images revealed a significant effect of precursor type on nanoparticles morphology. It was found that powder prepared from chloride salts is more porous than that prepared with nitrate salts. The estimated surface area of LaFeO3 nanoparticles ranges between 5.94 and 11.56 m2/g and the band gap varies from 2.19 to 2.27 eV. Methylene blue (MB) dye was used to investigate the catalytic and photocatalytic properties of LaFeO3 powders. Both prepared powder types showed good catalytic activity and high photocatalytic performance under visible irradiation in removing MB dye. The adsorption kinetics data of MB molecules on LaFeO3 nanoparticles are well fitted to the pseudo-first order model. Powder synthesized with chloride salts demonstrated high photodegradation efficiency of MB dye compared to that prepared by nitrate salts, which can be attributed to its relatively small band gap and high porosity. These two factors ensure a greater number of photogenerated electrons and more sites for photocatalytic reactions.

Observing zinc oxide nanoparticles suspension stability in various media by using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS)

Zinc oxide (ZnO) nanoparticles are widely used in industry due to their ability to absorb UV light and antibacterial property. The total surface area of ZnO nanoparticles affects its properties and applications. Therefore, the size and stability control of ZnO nanoparticles is very important. We explored the ability of single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) in combination with settling process to analyze ZnO nanoparticles suspended in various media, by which the method allows to detect specific nanoparticles at very low concentration. The settling experiment of ZnO nanoparticles suspended in various media, including deionized water, non-ionic, cationic and anionic surfactants, was carried out to study size, stability and dispersion. The SP-ICP-MS along with settling experiment was set up by suspending different sizes of ZnO nanoparticles in deionized water, Triton X-100, cetyltrimethylammonium bromide and sodium dodecyl sulfate, followed by collecting the sample at various times and vertical distances. Then, the collected samples were diluted and analyzed by SP-ICP-MS to obtain the information on particle size distribution and the particle number concentration. The size and morphology of the ZnO nanoparticles were observed by transmission electron microscopy technique and zeta potential values of particles suspension were measured. The total concentrations of Zn in the suspension were also analyzed by conventional mode ICP-MS to compare with single particle mode ICP-MS. The information obtained in this work allows us to assess the stability of ZnO nanoparticles in various media and shows that the newly developed approach based on SP-ICP-MS with settling experiment can be used as an alternative characterization tool to evaluate the stability of nanoparticles.

Hybridization of cellulose nanocrystals modified ZnO nanoparticles with bio-based hyperbranched waterborne polyurethane sizing agent for superior UV resistance and interfacial properties of CF/PA6 composites

The interface of carbon fiber (CF) reinforced composites has been a long challenging issue that restricts the full utilization of its excellent properties in industrial applications. In present work, a green solvent γ-valerolactone and biogenetic derived gallic acid and tartaric acid were used to prepare a hyperbranched waterborne polyurethane (HWPU) sizing agent. Meanwhile, cellulose nanocrystal modified zinc oxide (CNC–ZnO) nanohybrids were successfully synthesized using a facile one-pot method to improve the dispersibility and specific surface area of ZnO nanoparticles. The hybridization of CNC–ZnO substantially enhanced the thermostability and UV resistance of bio-based HWPU. The mechanical properties of the modified composites were thoroughly examined, revealing remarkable enhancements in flexural strength and interlaminar shear strength, with improvements of 46.5 % and 48.1 % compared to pristine CF. Additionally, the interfacial shear strength test demonstrated a significant increase of 63.6 %. Remarkably, the modified carbon fiber composites retained more than 97 % of their mechanical properties after being subjected to continuous xenon irradiation for a week, highlighting the exceptional ultroviolet resistance derived from the hybrid HWPU sizing agent.

In situ synthesis and stabilization of PVP-coated aluminum nanoparticles by one-step pulsed laser ablation in liquid: Investigation and quantification of PVP coverage effects

This study explored the use of one-step pulsed laser ablation (PLA) in liquid process for in situ synthesis of polyvinylpyrrolidone (PVP) coated highly-stabilized Al nanoparticles (NPs). The effect of different process variables such as laser energy, PVP concentration, and PVP chain length on the composition, size, distribution, and stability of the synthesized NPs was investigated. The results showed that adding PVP to the solution led to smaller average size of NPs with a more uniform distribution, and enhanced resistance to aggregation. This study also revealed that while PVP only partially inhibited the reaction between Al NPs and oxygen during NP generation, it could provide excellent blocking performance against hydroxylation to NPs in subsequent aging experiments. The concept of polymer coverage was introduced to quantify the protective effect of PVP polymers on Al NPs. At 0.1 J laser energy and a K-30 PVP concentration of 10 g/L, a polymer coverage value of 6773 was achieved, maximizing the amount of polymer per unit NP surface area. It was verified that Al NPs' reactivity was most efficiently suppressed under this condition. However, it was observed that the critical polymer coverage value required to suppress the reaction of Al NPs with their surroundings depended on process variables such as laser energy and polymer chain length. This study also confirmed that using high molecular weight polymers can further improve the anti-agglomeration performance and ablation efficiency while lowering the required critical polymer coverage value.

Validating Electrochemical Active Surface Area Determination of Nanostructured Electrodes: Surface Oxide Reduction on AuPd Nanoparticles

Accurate normalization of electrochemical active surface area (ECSA) of nanostructured catalysts and nanoparticles is of utmost importance for catalyst activity determination and comparability. AuxPdy nanoparticles are a highly interesting example, as electrocatalysts for selective oxygen reduction reaction and alcohol oxidation. Most techniques used today for ECSA determination lack accurate validation for nanostructured electrodes and instead rely on reference values determined for macroelectrodes. This includes ECSA determination for AuxPdy nanoparticles, most commonly done by potentiodynamic surface oxide reduction. Here we suggest a versatile approach to validate different ECSA determination techniques for nanoparticle-modified or nanostructured electrodes, using surface oxide reduction of AuxPdy as an illustrative example. Combining this with volume determination by anodic stripping, we electrochemically estimate the NP diameter, which serves as an indication of the accuracy of the obtained ECSA values. Showcasing this for different nanoparticle compositions, we provide experimental conditions for determining AuxPdy nanoparticle ECSA using surface oxide reduction and compare those to parameters reported for macroelectrodes. The approach we introduce herein can be readily applied to a number of different alloy systems, thus, providing a widely applicable approach to determine electrochemical surface areas and validate the transferability of existing macroelectrode characterization techniques to nanostructured or nanoparticle-modified electrodes.

On the structural and optical characterization of zinc aluminate nanoparticles synthesized via green microwave route

Zinc aluminate, a widely employed wide bandgap semiconductor, boasts exceptional mechanical and thermal properties, coupled with a high quantum yield. Its versatile applications include photocatalytic pollutant degradation, utilization in displays, and contributions to the medicinal field. However, challenges arise during synthesis processes, where high-temperature annealing reduces nanoparticle surface area, and cation contamination from precursors impacts material purity. In response to these challenges, green synthesis methods incorporating plant extracts as reductants have emerged to yield higher-quality phosphors. In this study, the focus is on microwave synthesis of Zinc Aluminate using Zinc Nitrate and Aluminum Nitrate in varying ratios as precursors. Comprehensive structural and optical characterizations, including X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Diffuse Reflectance Spectroscopy (DRS), and Photoluminescence Spectroscopy (PL), have been conducted to assess the influence of precursor molar ratios on the spinel growth and optimization of the synthesis process.