Role of Capping Agent in Wet Synthesis of Nanoparticles

Vacancy-Rich SnO2 Quantum Dot Stabilized by Polyoxomolybdate as Electrocatalyst for Selective NH3 Production

The pronounced conductivity of tin dioxide (SnO2) nanoparticles makes it an ideal multifunctional electrode material, while the challenge is to stabilize the quantum dot (QD) SnO2 nanocore in water. An Anderson-type polyoxomolybdate, (NH4)6[Mo7O24], is employed as an inorganic ligand to stabilize a ca. 6 nm SnO2 QD (Mox@SnO2). X-ray scattering and diffraction studies confirm the tetragonal SnO2 nanocore in Mox@SnO2. Elemental analyses are in good agreement with the mass spectrometric detection of the [Mo7O24]6- cluster present in Mox@SnO2. The ionic POMs attached to the SnO2 surface through [Mo-O-Sn] covalent linkages have been established by surface zeta potential, shift of the [Mo = O]t Raman vibration, and extended X-ray absorption fine structure (EXAFS) analyses. The presence of the [Mo7O24]6- cluster in the Mox@SnO2 is responsible for the remarkable aqueous stability of Mox@SnO2 in the pH range of 3-9. Dominant oxygen vacancy in the SnO2 core, identified by EXAFS data and the anisotropic electron paramagnetic resonance (EPR) signals (g ∼ 2.4 and 1.9), results in facile electronic conduction in Mox@SnO2 while being deposited on the electrode surface. Mox@SnO2 acts as an active catalyst for the electrocatalytic nitrate reduction (eNOR) to ammonia with 94% faradaic efficiency (FE) at -0.2 V vs RHE and a yield rate of 28.9 mg h-1 cm-2. The stability of Mox@SnO2 in acidic pH provides scope to reuse the Mox@SnO2 electrode at least four times with notable NH3 selectivity and a superior production rate (239.06 mmol g-1(cat) h-1). This study demonstrates the essential role of POM in stabilizing SnO2 QD, harnessing its electrochemical activity toward electrocatalytic ammonia production.

Light switching for product selectivity control in photocatalysis

Artificial switchable catalysis is a new, rapidly expanding field that offers great potential advantages for both homogeneous and heterogeneous catalytic systems. Light irradiation is widely accepted as the best stimulus to artificial switchable chemical systems. In recent years, tremendous progress has been made in the synthesis and application of photo-switchable catalysts that can control when and where bond formation and dissociation take place in reactant molecules. Photo-switchable catalysis is a niche area in current catalysis, on which systematic analysis and reviews are still lacking in the scientific literature, yet it offers many intriguing and versatile applications, particularly in organic synthesis. This review aims to highlight the recent advances in photo-switchable catalyst systems that can result in two different chemical product outcomes and thus achieve a degree of control over organic synthetic reactions. Furthermore, this review evaluates different approaches that have been employed to achieve dynamic control over both the catalytic function and the selectivity of several different types of synthesis reactions, along with the remaining challenges and potential opportunities. Owing to the great diversity of the types of reactions and conditions adopted, a quantitative comparison of efficiencies between considered systems is not the focus of this review, instead the review showcases how insights from successful adopted strategies can help better harness and channel the power of photoswitchability in this new and promising area of catalysis research.

Silver oxide decorated urchin-like microporous organic polymer composites as versatile antibacterial organic coating materials

Microporous organic polymers (MOPs) and metal oxide hybrid composites are considered valuable coating materials because of their versatility derived from the synergistic combination of MOPs' inherent dispersibility and the distinctive properties of metal oxides. In this study, we present the synthesis of sea-urchin-like MOPs hybridised with silver oxide nanoparticles (Ag2O NPs) to fabricate antibacterial composites suitable for potential antibacterial coating applications. Ag2O NP-decorated urchin-like MOPs (Ag2O@UMOPs) were synthesised by employing a combination of two methods: a one-pot Lewis acid-base interaction-mediated self-assembly and a straightforward impregnation process. The as-prepared Ag2O@UMOPs demonstrated high antibacterial efficacy against both E. coli (G-) and S. aureus (G+). The antibacterial mechanism of Ag2O@UMOPs mainly involved the synergistic effects of accumulation of Ag2O@UMOPs, the release of Ag+ ions, and the generation of reactive oxygen species. The exceptional processability and biosafety of Ag2O@UMOPs make them ideal organic coating materials for convenient application on various substrates. These remarkable features of Ag2O@UMOPs provide an effective platform for potential antibacterial applications in biological sciences.

Superior functionality of niobium pentoxide nano-rod/tripod photocatalyst synthesized using polyethyleneimine as a soft template for the abatement of methylene blue under UV and visible irradiation

Polyethyleneimine (PEI) capping agent-cum-template-mediated synthesis of niobium oxide nanoparticles is reported to explore its impact on the resultant morphology, porosity, crystallinity, phase complexation, and thus on the photocatalytic activity. The resultant niobium oxides calcined at 800°C and 1000°C crystallized into highly ordered nano-rod/tripod nanostructure with inter-rod angle <120° having orthorhombic phase and heavily agglomerated rod-like nanostructures having monoclinic crystal phase, respectively. Contrary to the expectations, the nano-rod/tripods showed superior photocatalytic degradation kinetics and high adsorption of methylene blue dye in the hydrocolloid than formerly reported monoclinic nanoparticles. The best adsorption capability and photocatalytic activity are observed for the sample calcined at 800°C, resulting in a combined degradation efficiency of 98.8% of methylene blue dye. The adsorption characteristics, stability of the hydrocolloid system, the existence of oxygen vacancies, and the distinct morphology of the photocatalytic nano-rod/tripods are mainly responsible for this behavior. The process and the performance of unique nanostructure over others presents a superior alternative.

Colloidal Polymer-Templated Formation of Inorganic Nanocrystals and their Emerging Applications

Inorganic nanocrystals possess unique physicochemical properties compared to their bulk counterparts. Stabilizing agents are commonly used for the preparation of inorganic nanocrystals with controllable properties. Particularly, colloidal polymers have emerged as general and robust templates for in situ formation and confinement of inorganic nanocrystals. In addition to templating and stabilizing inorganic nanocrystals, colloidal polymers can tailor their physicochemical properties such as size, shape, structure, composition, surface chemistry, and so on. By incorporating functional groups into colloidal polymers, desired functions can be integrated with inorganic nanocrystals, advancing their potential applications. Here, recent advances in the colloidal polymer-templated formation of inorganic nanocrystals are reviewed. Seven types of colloidal polymers, including dendrimer, polymer micelle, stare-like block polymer, bottlebrush polymer, spherical polyelectrolyte brush, microgel, and single-chain nanoparticle, have been extensively applied for the synthesis of inorganic nanocrystals. Different strategies for the development of these colloidal polymer-templated inorganic nanocrystals are summarized. Then, their emerging applications in the fields of catalysis, biomedicine, solar cells, sensing, light-emitting diodes, and lithium-ion batteries are highlighted. Last, the remaining issues and future directions are discussed. This review will stimulate the development and application of colloidal polymer-templated inorganic nanocrystals.

Impact of Surface Oxidation on the Morphology of Uranium Dioxide Nanoparticles

The undeniable importance of nanoparticles has led to vast efforts, in many fields of science, to understand their chemical and physical properties. In this paper, the morphology dependence of f-element nanoparticles is correlated to the oxygen environment and the type and coverage of capping ligands. This dependence was evaluated by first-principles calculations of the surface energies of different crystallographic planes (001, 110, and 111) as a function of the relative oxygen chemical potential and under the influence of different ligands. Uranium dioxide nanoparticles were the focus of this study due to their high sensitivity to oxidation compared to thorium dioxide nanoparticles, a homoleptic material but insensitive to oxidation. To fully explain the experimental observations of uranium dioxide nanocrystals, theoretical modeling shows that the consideration of surfaces with different oxidation conditions is necessary. It is shown that, for materials with low oxidation potential, such as uranium dioxide, the oxygen environment and capping ligand concentration are competing factors in determining the nanoparticle morphology.

Elucidating the Role of Capping Agents in Facet-Dependent Adsorption Performance of Hematite Nanostructures

Organic capping agents are a ubiquitous and crucial part of preparing reproducible and homogeneous batches of nanomaterials, particularly nanocrystals with well-defined facets. Despite studies reporting surface ligands (e.g., capping agents) having a non-negligible role in catalytic behavior, their impact is less understood in contaminant adsorption, an important consideration given their potential to obfuscate facet-dependent trends in performance. To ascribe observed behaviors to the facet or the ligand, this report evaluates the impact of poly(N-vinyl-2-pyrrolidone) (PVP), a commonly utilized capping agent, on the adsorption performance of nanohematite particles of varying prevailing facet in the removal of selenite (Se(IV)) as a model system. The PVP capping agent reduces the available surface area for contaminant binding, thus resulting in a reduction in overall Se(IV) adsorbed. However, accounting for the effects of surface area, {012}-faceted nanohematite demonstrates a significantly higher sorption capacity for Se(IV) compared with that of {001}-faceted nanohematite. Notably, chemical treatment is minimally effective in removing strongly bound PVP, indicating that complete removal of surface ligands remains challenging.

Boosted visible-light-driven degradation over stable ternary heterojunction as a plasmonic photocatalyst: Mechanism exploration, pathway and toxicity evaluation

The incorporation of plasmonic metals into semiconductors forming heterojunction photocatalysts is a promising route to enhance the photocatalytic performance in visible light. In this work, we reported the visible-light-driven one-dimensional (1D) nanostick silver/silver sulfide (Ag/Ag₂S) photocatalyst combining with two-dimensional (2D) nanosheet reduced graphene oxide intersected by hollow structure (h-RGO) was prepared via a feasible approach at room temperature. The density of Ag depositing on the surface of Ag₂S was easily tuned by the concentration of sodium borohydride and the silicon dioxide nanospheres were employed as templates in the preparation of h-RGO by the layer-by-layer (LBL) assembly. The ternary plasmonic Ag/Ag₂S/h-RGO photocatalysts exhibited better photocatalytic performance for degradation of naphthalene (95.95%) and 1-naphthol (98.65%) under visible light than the pure Ag₂S, composite Ag/Ag₂S and composite Ag/Ag₂S/RGO. Localized surface plasmon resonance of Ag, heterojunction formed between Ag/Ag₂S and RGO and the unique characteristics of h-RGO, which included higher specific surface areas, more efficient reflections of light and more active sites than RGO for boosting separation efficiency of charge carriers, were all responsible for such enhancement. By combining the characterization results with various computations, the mechanism, potential degradation pathways and the toxicity of the generated intermediates for photodegradation were examined. In addition to offering profound insight into the expansion of effective plasmonic photocatalysts with novel structures, the current study is beneficial to ease the environmental crisis to a certain extent.

Structural parameters of nanoparticles affecting their toxicity for biomedical applications: a review

Rapidly growing interest in using nanoparticles (NPs) for biomedical applications has increased concerns about their safety and toxicity. In comparison with bulk materials, NPs are more chemically active and toxic due to the greater surface area and small size. Understanding the NPs' mechanism of toxicity, together with the factors influencing their behavior in biological environments, can help researchers to design NPs with reduced side effects and improved performance. After overviewing the classification and properties of NPs, this review article discusses their biomedical applications in molecular imaging and cell therapy, gene transfer, tissue engineering, targeted drug delivery, Anti-SARS-CoV-2 vaccines, cancer treatment, wound healing, and anti-bacterial applications. There are different mechanisms of toxicity of NPs, and their toxicity and behaviors depend on various factors, which are elaborated on in this article. More specifically, the mechanism of toxicity and their interactions with living components are discussed by considering the impact of different physiochemical parameters such as size, shape, structure, agglomeration state, surface charge, wettability, dose, and substance type. The toxicity of polymeric, silica-based, carbon-based, and metallic-based NPs (including plasmonic alloy NPs) have been considered separately.

Synthesis of cobalt aluminates by using the peel extracts of Citrus family species

Synthesis of cobalt aluminate was achieved by using the peel extracts of Citrus family species. The peel extracts of lemon, orange and mandarin were used as capping agent in experimental step. These peels were extracted through varied solvents including water, ethanol and methanol. In this regard, the efficacies of the peel type and the extraction liquid were surveyed in the study, using a co-precipitation technique in the synthesis of CoAl2O4 spinel. Samples compared in different parameters were subjected to a range of analyses consisting of colorimetry, X-Ray Diffraction, Scanning Electron Microscope and thermal examinations. The minimum b * value was reached as –14.23 in the sample with a capping agent provided by the orange peel extract, extraction liquid of which is water. The results denoted successful crystal structure scores and single-phase CoAl2O4 formation as well as the occurrence of a double-phase configuration. The highest XRD score of 83 was obtained for CoAl2O4. Considering SEM results, the lowest and highest particle size distributions were found between 100–150 nm and 350–800 nm, respectively. In the research, cobalt aluminate synthesis was carried out by means of modifying agents prepared with the peels of Citrus family species using different solvents.

Rapid detection of bacteria using gold nanoparticles in SERS with three different capping agents: Thioglucose, polyvinylpyrrolidone, and citrate

The increase in outbreaks of emerging and re-emerging bacterial infections over the last few decades calls for their rapid detection and treatment. Surface-enhanced Raman spectroscopy (SERS) is a technique that can be applied to develop fast screening systems for bacterial presence in biological samples. Optimizing the capping agents in nanoparticle synthesis is important because capping agents are responsible for controlling the morphological features and chemical properties of the nanoparticles that are essential for SERS. To the best of our knowledge, this paper is the first to study the application of gold nanoparticles capped with thioglucose and polyvinylpyrrolidone (PVP) in SERS detection of bacteria as an alternative to the citrate-capped gold nanoparticles that are often used in SERS detection of bacteria. Three different species of bacteria were used in this study: Cutibacterium acnes, Escherichia coli and Staphylococcus aureus (methicillin-sensitive and methicillin-resistant). This study demonstrates that the thioglucose, citrate both show good contribution in bacterial species identification and the thioglucose shows the best among the three capping agents in two types of S. aureus identification. Moreover, although PVP showed high Raman peaks in the SERS spectrum for each type of bacteria, it showed least contribution in identifying species and strains due to its low efficacy in producing responses from different nucleic acid components in the bacteria cells.

Synthesis of N-myristoyltaurine stabilized gold and silver nanoparticles: Assessment of their catalytic activity, antimicrobial effectiveness and toxicity in zebrafish

In this paper, the application of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) synthesized using a biomimetic lipid, N-myristoyltaurine (N14T) was evaluated in common fields. The catalytic effectiveness of AgNPs and AuNPs was studied in the popular nanocatalyst reaction, nitroaromatic reduction, and dye degradation. Both NPs display catalytic activity in the nitroaromatic compound and organic dyes reduction reaction involving sodium borohydride and the rate constant is estimated as 10^-3 s^-1. Strikingly, the reaction initiation time (t₀) and completion time (t_c) differ significantly between AgNPs and AuNPs. Analyzing the reaction kinetic profile revealed that the reaction carried out with AuNPs showed a shorter t₀ and t_c, suggesting a better catalyst than AgNPs. In addition, the efficiency of the NPs was examined in Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa). In difference to the catalytic study, AuNPs display poor antibacterial activity. Whereas AgNPs kill the tested bacteria at 250 μM via disturbing bacterial membrane integrity and produce excess reactive oxygen species. The toxicology study carried out with zebrafish animal model reveals that both AgNPs and AuNPs are non-toxic. The findings suggest that each nanomaterial possesses unique physicochemical properties irrespective of stabilization with the same molecules.

Synthetic Conditions, Physical Properties, and Antibacterial Activities of Silver Nanoparticles with Exopolysaccharides of a Medicinal Fungus

Natural polysaccharides are attractive and promising biomacromolecules for the green synthesis of silver nanoparticles (Ag NPs) with a broad spectrum of useful functions. This study aims to evaluate the synthetic conditions and physical properties of Ag NPs using three fractions of exopolysaccharide (EPS), namely EPS-1, EPS-2, and EPS-3, produced by a medicinal fungus known as Cs-HK1, with variations in their chemical composition and molecular weight. Each of the EPS fractions had a unique set of optimal synthetic conditions (reaction time course, temperature, and reagent concentration), resulting in a specific range of Ag NP size distributions. The Ag NPs synthesized with the EPS-1 fraction had the smallest particle size (~160 nm) and the most significant antibacterial activities against Escherichia coli (Gram-) and Staphylococcus aureus (Gram+), with a minimal inhibitory concentration (MIC) of 0.2 mg/mL on E. coli and 0.075 mg/mL on S. aureus. The results proved the success of the scheme of this green synthesis scheme with all three EPS fractions and the potential antibacterial application of EPS-coated Ag NPs.

Ag2O Nanoparticles as a Candidate for Antimicrobial Compounds of the New Generation

Antibiotic resistance in microorganisms is an important problem of modern medicine which can be solved by searching for antimicrobial preparations of the new generation. Nanoparticles (NPs) of metals and their oxides are the most promising candidates for the role of such preparations. In the last few years, the number of studies devoted to the antimicrobial properties of silver oxide NPs have been actively growing. Although the total number of such studies is still not very high, it is quickly increasing. Advantages of silver oxide NPs are the relative easiness of production, low cost, high antibacterial and antifungal activities and low cytotoxicity to eukaryotic cells. This review intends to provide readers with the latest information about the antimicrobial properties of silver oxide NPs: sensitive organisms, mechanisms of action on microorganisms and further prospects for improving the antimicrobial properties.

Influence of Polyvinylpyrrolidone Concentration on Properties and Anti-Bacterial Activity of Green Synthesized Silver Nanoparticles

Environmentally green synthesis of stable polyvinyl pyrrolidone (PVP)-capped silver nanoparticles (PVP-AgNPs) was successfully carried out. The present study focused on investigating the influence of adding PVP during the synthesis process on the size, optical properties and antibacterial effect of silver nanoparticles produced. An aqueous extract of Eucalyptus camaldulensis leaves was used as a reducing agent. The effects of different PVP concentrations and reducing time on the synthesis of nanoparticles (NPs) were characterized by UV–Vis spectrophotometry, scanning electron microscopy (SEM), energy dispersive spectrum (EDX), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and nano tracker analysis (NTA). The addition of PVP was studied. The prepared PVP-AgNPs were spherical with an average size of 13 nm. FTIR analysis confirmed that PVP protects AgNPs by a coordination bond between silver nanoparticles and both N and O of PVP. DLS results indicated the good dispersion of silver nanoparticles. PVP-AgNPs were found to be stable for nearly 5 months. Antibacterial studies through the agar well diffusion method confirmed that silver nanoparticles synthesized using PVP had no inhibitor activity toward Gram-positive and Gram-negative bacteria as opposed to silver nanoparticles prepared without adding PVP, which showed a significant antibacterial activity towards some of the tested pathogens.

Evaluation of the Structural Deviation of Cu/Cu2O Nanocomposite Using the X-ray Diffraction Analysis Methods

We successfully synthesized Cu/Cu2O nanocomposites using the wet chemical synthesis method. All X-ray diffraction (XRD), Reference Intensity Ratio (RIR), and Rietveld refinement methods confirmed that the compounds Cu and Cu2O are free of impurities. Scanning Electron Microscope (SEM) and Transmission electron microscopy (TEM) images show the morphology and interactions of Cu and Cu2O in the structure. The formation mechanism is also explained by five stages: precursor, nucleation, growth, aging, and reduction. The changes in crystallization parameters under variations in reaction temperature (Tv) and stirring speed (Sv) were confirmed by agreement with the XRD database. The lattice constant in the crystal of nanocomposite increases with rising temperature in the reaction, leading to unit cell expansion, while increasing the stirring—rate leads to a random size distribution of the lattice parameter. Due to the imperfect growth of the crystal, the induced crystallite size was calculated using the Williamson-Hall model, and the precise lattice parameter values were calculated using the Nelson-Riley function.

The Nature of Active Sites in the Pd/C-Catalyzed Hydrogenation/Hydrodeoxygenation of Benzaldehyde

Hydrogenations and hydrodeoxygenations represent two of the most important reactions in the production of both bulk and fine chemicals. Despite the wide and long use of metal-based catalysts for this reaction, there is still some uncertainty with respect to the properties governing the catalyst activity. Using the hydrogenation of benzaldehyde as a model reaction, in this paper, we disclose the dominant parameters determining catalyst activity of Pd nanoparticles supported on a carbonaceous material (carbon nanoplates, GNP). In particular, several operating parameters of the catalyst synthesis were varied in order to obtain materials with differences in such physico-chemical properties as nanoparticle size, Pd oxidation state and Pd surface exposure. A linear correlation between catalyst activity and the amount of surface Pd(0) atoms was found; this dependence, maintained after catalyst recycling, pointed out the nature of the active site of the Pd/GNP catalyst represented by exposed Pd(0) species.

Green Production of Zero-Valent Iron (ZVI) Using Tea-Leaf Extracts for Fenton Degradation of Mixed Rhodamine B and Methyl Orange Dyes

The danger from the content of dyes produced by textile-industry waste can cause environmental degradation when not appropriately treated. However, existing waste-treatment methods have not been effective in degrading dyes in textile waste. Zero-valent iron (ZVI), which has been widely used for wastewater treatment, needs to be developed to acquire effective green production. Tea (Camellia sinensis) leaves contain many polyphenolic compounds used as natural reducing agents. Therefore, this study aims to synthesize ZVI using biological reducing agents from tea-leaf extract and apply the Fenton method to degrade the color mixture of rhodamine B and methyl orange. The results show that the highest polyphenols were obtained from tea extract by heating to 90 °C for 80 min. Furthermore, PSA results show that ZVI had a homogeneous size of iron and tea extract at a volume ratio of 1:3. The SEM-EDS results show that all samples had agglomerated particles. The ZVI 1:1 showed the best results, with a 100% decrease in the color intensity of the dye mixture for 60 min of reaction and a degradation percentage of 100% and 66.47% for rhodamine B and methyl orange from LC-MS analysis, respectively. Finally, the decrease in COD value by ZVI was 92.11%, higher than the 47.36% decrease obtained using Fe(II).

Simulations to Aid in the Design of Microbes for Synthesis of Metallic Nanomaterials

Microbes are champions of nanomaterial synthesis. By virtue of their incredible native range─from thermal vents to radioactive soil─microbes evolved tools to thrive on inorganic material, and, in their normal course of living, forge nanomaterials. In recent decades, synthetic biologists have engineered a vast array of functional nanomaterials using genetic tools that control the natural ability of bacteria to perform complex redox chemistry, maintain steep chemical gradients, and express biomolecular scaffolds. Leveraging microbial biology can lead to intricate nanomaterial architectures whose design and assembly exists beyond the ken of inorganic methods. Theories enumerating microbial nanomaterial synthesis are spare, however, despite the advantage they could offer. Here, we describe a theoretical approach to simulating biogenic nanomaterial synthesis that incorporates key features and parameters of Gram-negative bacteria. By adapting previously verified inorganic theories of nanoparticle synthesis, we recapitulate past biogenic experiments, such as the ability to localize nanoparticle synthesis or regulate nucleation of specific nanomaterials. Moreover, the simulation offers direction in the design of future experiments. Our results demonstrate the promise of marrying experimental and theoretical approaches to microbial nanomaterial synthesis.

Magnetic and optical properties of green synthesized nickel ferrite nanoparticles and its application into photocatalysis

Spinel NiFe₂O₄nanoparticles have been synthesized via hydrothermal route usingMangifera indicaflower extract (MIFE) as a green surfactant and reducing agent. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy techniques have been used to determine the structure and morphology. The formation of single-phase, monodispersed NiFe₂O₄with mixed morphology, the predominant shape being of equi-axed nanoparticles having an average particle size ≲45 nm, is observed. The thermal magnetization of as-synthesized NiFe₂O₄nanoparticles shows ferromagnetic to paramagnetic phase transition atT_c ∼ 825 K. These nanoparticles show a very high saturation magnetization (M_s) value of 55 emu g^-1close to the bulk material and amongst the highest reported values for green synthesized NiFe₂O4 nanoparticles. This material has a coercivity (H_c) of 0.15 kOe and remanent magnetization (M_r) of 8.5 emu g^-1. The as-synthesized NiFe₂O₄nanoparticles show bandgap energy of 2.02 eV, derived from UV-vis absorption measurement, which is suitable for effective solar photocatalytic reactions. When exposed to sunlight in the presence of as-synthesized NiFe₂O₄nanoparticles, 93% of MB-dye degradation is measured in 80 min, indicating excellent photocatalytic properties. Based on the as-synthesized NiFe₂O₄nanoparticles' observed properties, the effectiveness of MIFE as an environmentally friendly surfactant, and the low-cost dye-degradation prospects of green synthesized NiFe₂O₄nanoparticles are affirmed.

Defect engineering of oxide perovskites for catalysis and energy storage: synthesis of chemistry and materials science

Oxide perovskites have emerged as an important class of materials with important applications in many technological areas, particularly thermocatalysis, electrocatalysis, photocatalysis, and energy storage. However, their implementation faces numerous challenges that are familiar to the chemist and materials scientist. The present work surveys the state-of-the-art by integrating these two viewpoints, focusing on the critical role that defect engineering plays in the design, fabrication, modification, and application of these materials. An extensive review of experimental and simulation studies of the synthesis and performance of oxide perovskites and devices containing these materials is coupled with exposition of the fundamental and applied aspects of defect equilibria. The aim of this approach is to elucidate how these issues can be integrated in order to shed light on the interpretation of the data and what trajectories are suggested by them. This critical examination has revealed a number of areas in which the review can provide a greater understanding. These include considerations of (1) the nature and formation of solid solutions, (2) site filling and stoichiometry, (3) the rationale for the design of defective oxide perovskites, and (4) the complex mechanisms of charge compensation and charge transfer. The review concludes with some proposed strategies to address the challenges in the future development of oxide perovskites and their applications.

Hierarchical Nanoflowers of Colloidal WS2 and Their Potential Gas Sensing Properties for Room Temperature Detection of Ammonia

A one-step colloidal synthesis of hierarchical nanoflowers of WS2 is reported. The nanoflowers were used to fabricate a chemical sensor for the detection of ammonia vapors at room temperature. The gas sensing performance of the WS2 nanoflowers was measured using an in-house custom-made gas chamber. SEM analysis revealed that the nanoflowers were made up of petals and that the nanoflowers self-assembled to form hierarchical structures. Meanwhile, TEM showed the exposed edges of the petals that make up the nanoflower. A band gap of 1.98 eV confirmed a transition from indirect-to-direct band gap as well as a reduction in the number of layers of the WS2 nanoflowers. The formation of WS2 was confirmed by XPS and XRD with traces of the oxide phase, WO3. XPS analysis also confirmed the successful capping of the nanoflowers. The WS2 nanoflowers exhibited a good response and selectivity for ammonia.

Green synthesis of silver nanoparticles with algae and the importance of capping agents in the process

BACKGROUND

Nanoparticle synthesis is a very interesting area of research currently due to the wide applications of nanoparticles. The nanoparticles have a diameter ranging between 1 and 100 nm and they are used in different fields like electronics, pharmaceuticals, cosmetics, biotechnology, medicines, etc. Nanoparticles have gained the interest of researchers due to their large surface-to-volume ratio and their capability to interact effectively with other particles. Several different methods can be used for the production of silver nanoparticles (AgNPs) including chemical, physical, and biological. Out of all the methods, the biological method is considered the cleanest and safest as no toxic chemicals are used in the process. The biological method includes the use of bacteria, fungi, algae, and plant extract for the synthesis. Algal synthesis of AgNPs is especially interesting because of the high capacity of the algae to take in metals and reduce metal ions. Algae is a widely distributed organism and its availability is abundant; an added advantage is their growth under laboratory conditions. These organisms can help in large-scale production at a low cost.

SHORT CONCLUSION

This review article explains the different factors that should be considered for the effective synthesis of AgNPs using algae. Capping agents also affect the stability of nanoparticles. It also sheds light on the importance of capping agents in the synthesis of AgNPs. Alga-mediated synthesis of AgNPs along with the use of different capping agents can help in modulating the stability and size of the nanoparticles, thereby improving its cost-effectiveness and environment-friendly production.

Colloidal synthesis of metal chalcogenide nanomaterials from metal-organic precursors and capping ligand effect on electrocatalytic performance: progress, challenges and future perspectives

Renewable and sustainable functional nanomaterials, which can be employed in alternative green energy sources, are highly desirable. Transition metal chalcogenides are potential catalysts for processes resulting in energy generation and storage. In order to optimize their catalytic performance, high phase purity and precise control over shape and size are indispensable. Metal-organic precursors with pre-formed bonds between the metal and the chalcogenide atoms are advantageous in synthesizing phase pure transition metal chalcogenides with controlled shape and sizes. This can be achieved by the decomposition of metal-organic precursors in the presence of suitable surfactants/capping agents. However, the recent studies on electrocatalysis at the nanoscale level reveal that the capping agents attached to their surface have a detrimental effect on their efficiency. The removal of surfactants from active sites to obtain bare surface nanoparticles is necessary to enhance catalytic activity. Herein, we have discussed the properties of different metal-organic precursors and the role of surfactants in the colloidal synthesis of metal chalcogenide nanomaterials. Moreover, the effect of surfactants on their electrocatalytic performance, the commonly used strategies for removing surfactants from the surface of nanomaterials and the future perspectives are reviewed.

Engineering Biological Electron Transfer and Redox Pathways for Nanoparticle Synthesis

Many species of bacteria are naturally capable of types of electron transport not observed in eukaryotic cells. Some species live in environments containing heavy metals not typically encountered by cells of multicellular organisms, such as arsenic, cadmium, and mercury, leading to the evolution of enzymes to deal with these environmental toxins. Bacteria also inhabit a variety of extreme environments, and are capable of respiration even in the absence of oxygen as a terminal electron acceptor. Over the years, several of these exotic redox and electron transport pathways have been discovered and characterized in molecular-level detail, and more recently synthetic biology has begun to utilize these pathways to engineer cells capable of detecting and processing a variety of metals and semimetals. One such application is the biologically controlled synthesis of nanoparticles. This review will introduce the basic concepts of bacterial metal reduction, summarize recent work in engineering bacteria for nanoparticle production, and highlight the most cutting-edge work in the characterization and application of bacterial electron transport pathways.

Metal Doped PVA Films for Opto-Electronics-Optical and Electronic Properties, an Overview

Polyvinyl alcohol is unique among polymers. Apart from its preparation, it is not built up in polymerization reactions from monomers, unlike most vinyl-polymers, and it is biodegradable in the presence of suitably acclimated microorganisms. It is an environmentally friendly material for a wide range of applications, from medical ones, based on its biocompatibility, to integrated optics. This paper reviews, in addition to the preparation and optimization of films of polyvinyl alcohol doped with different metal species, the role of dopants and doping technologies in the involved electronic mechanism. The optical properties were studied by UV-VIS-IR, Mössbauer spectroscopy, and other measurement techniques, with applications such as real-time holography, microlasers, optical sensors or nanophotonics in mind.

Stabilizer-free bismuth nanoparticles for selective polyol electrooxidation

Bismuth is the least toxic element among heavy metals, an outstanding advantage for environmental and health considerations. Yet, utilizing bismuth as anodic electrocatalyst is hindered by the formation of a spreading Bi(OH)₃ inhibitor layer during the anodic process. Herein, we report that bismuth nanoparticles, produced using laser ablation, can avoid such drawbacks. The production of Bi(V) species assists polyol electrooxidation. For glucose, instead of the commonly reported gluconic acid as the product, the Bi(V) species enables highly selective oxidation and C–C bond cleavage to produce arabinonic acid, erythronic acid, and eventually glyceric acid. We not only generate high-valent Bi(V) species for catalytic applications, especially for bioelectrocatalysis where the less toxic bismuth is highly appreciated, but also present Bi nanoparticle as a highly selective electrocatalyst that can break C–C bond. We believe that Bi electrocatalyst can find broader applications in electrochemical biomass conversion and electrosynthesis.

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Stabilizer-free bismuth nanoparticles (Bi NPs) are synthesized by laser ablation

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Bi NPs show activity toward polyol electrooxidation, breaking C-C bond

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The in situ generated Bi(V) is essential for the electrocatalytic oxidation

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Unlike Bi polycrystal, surface oxide layers do not inhibit the activity of Bi NPs

Low-Temperature Synthesis of Titanium Oxynitride Nanoparticles

The synthesis of transition metal oxynitrides is complicated by extreme reaction conditions such as high temperatures and/or high pressures. Here, we show an unprecedented solution-based synthesis of narrowly dispersed titanium oxynitride nanoparticles of cubic shape and average size of 65 nm. Their synthesis is performed by using titanium tetrafluoride and lithium nitride as precursors alongside trioctylphosphine oxide (TOPO) and cetrimonium bromide (CTAB) as stabilizers at temperatures as low as 250 °C. The obtained nanoparticles are characterized in terms of their shape and optical properties, as well as their crystalline rock-salt structure, as confirmed by XRD and HRTEM analysis. We also determine the composition and nitrogen content of the synthesized particles using XPS and EELS. Finally, we investigate the applicability of our titanium oxynitride nanoparticles by compounding them into carbon fiber electrodes to showcase their applicability in energy storage devices. Electrodes with titanium oxynitride nanoparticles exhibit increased capacity compared to the pure carbon material.

A review of the role and mechanism of surfactants in the morphology control of metal nanoparticles

Although great progress has been made in the synthesis of metal nanoparticles, good repeatability and accurate predictability are still difficult to achieve. This difficulty can be attributed to the synthetic method based primarily on observation and subjective experience, and the role of many surfactants remains unclear. It should be noted that surfactants play an important role in the synthetic process. Understanding their function and mechanism in the synthetic process is a prerequisite for the rational design of nanocatalysts with ideal morphology and performance. In this review article, the function of surfactants is introduced first, and then the mechanism of action of surfactants in controlling the morphology of nanoparticles is discussed according to the types of surfactants, and the promoting and sealing effects of surfactants on the crystal surface is revealed. The relationship between surfactants and the morphology structure of nanoparticles is studied. The removal methods of surfactants are discussed, and the existing problems in the current development strategy are summarized. Finally, the application of surfactants in controlling the morphology of metal nanocrystals is prospected. It is hoped that the review can open up new avenues for the synthesis of nanocrystals.

Hybrid Nanosystems for Biomedical Applications

Inorganic/organic hybrid nanosystems have been increasingly developed for their versatility and efficacy at overcoming obstacles not readily surmounted by nonhybridized counterparts. Currently, hybrid nanosystems are implemented for gene therapy, drug delivery, and phototherapy in addition to tissue regeneration, vaccines, antibacterials, biomolecule detection, imaging probes, and theranostics. Though diverse, these nanosystems can be classified according to foundational inorganic/organic components, accessory moieties, and architecture of hybridization. Within this Review, we begin by providing a historical context for the development of biomedical hybrid nanosystems before describing the properties, synthesis, and characterization of their component building blocks. Afterward, we introduce the architectures of hybridization and highlight recent biomedical nanosystem developments by area of application, emphasizing hybrids of distinctive utility and innovation. Finally, we draw attention to ongoing clinical trials before recapping our discussion of hybrid nanosystems and providing a perspective on the future of the field.

Critical analysis of biophysicochemical parameters for qualitative improvement of phytogenic nanoparticles

Conventional chemical approaches for synthesizing nanoparticles (NPs) may restrict their applicability as they are not eco-friendly, energetically efficient and often involve toxic reducing/capping agents; but phytonanotechnology enabled the synthesis of safe, inexpensive, highly biocompatible NPs. In this regard, thorough understanding of green components and the modulatory effects of different reaction conditions on the physicochemical parameters of green synthesized NPs would be a prerequisite, which is not depicted elsewhere. This review critically analyzes the relevant reaction conditions from their mechanistic viewpoints in plant-based synthesis of NPs arising fundamental issues which need to be determined carefully. The size, stability and surface chemistry of phytogenic NPs may be fabricated as a function of multiple interconnected reaction parameters and the plant species used. The therapeutic potential of phytogenic NPs may depend on the plant species used; and so the meticulous understanding of physicochemical parameters and the family wise shorting of elite plant species may potentially benefit the theranostic future of plant-based NPs.

Synthesis of Metal Nanostructures Using Supercritical Carbon Dioxide: A Green and Upscalable Process

Metallic nanostructures have numerous applications as industrial catalysts and sensing platforms. Supercritical carbon dioxide (scCO₂ ) is a green medium for the scalable preparation of nanomaterials. Supercritical fluid reactive deposition (SFRD) and other allied techniques can be employed for the mass production of metal nanostructures for various applications. The present article reviews the recent reports on the scCO₂ -assisted preparation of zero-valent metal nanomaterials and their applications. A brief description of the science of pure supercritical fluids, especially CO₂ , and the basics of binary mixtures composed of scCO₂ and a low volatile substance, e.g., an organometallic precursor are presented. The benefits of using scCO₂ for preparing metal nanomaterials, especially as a green solvent, are also being highlighted. The experimental conditions that are useful for the tuning of particle properties are reviewed thoroughly. The range of modifications to the classical SFRD methods and the variety of metallic nanomaterials that can be synthesized are reviewed and presented. Finally, the broad ranges of applications that are reported for the metallic nanomaterials that are synthesized using scCO₂ are reviewed. A brief summary along with perspectives about future research directions is also presented.

A non-classical route of efficient plant uptake verified with fluorescent nanoparticles and root adhesion forces investigated using AFM

Classical plant uptake is limited to hydrophilic or water-dispersible material. Therefore, in order to test the uptake behaviour of hydrophobic particles, here, we tested the fate of hydrophobic particles (oleylamine coated Cu2-xSe NPs (CS@OA)) in comparison to hydrophilic particles (chitosan-coated Cu2-xSe NPs (CS@CH)) by treatment on the plant roots. Surprisingly, hydrophobic CS@OA NPs have been found to be ~ 1.3 times more efficient than hydrophilic CS@CH NPs in tomato plant root penetration. An atomic force microscopy (AFM) adhesion force experiment confirms that hydrophobic NPs experience non-spontaneous yet energetically favorable root trapping and penetration. Further, a relative difference in the hydrophobic vs. hydrophilic NPs movement from roots to shoots has been observed and found related to the change in protein corona as identified by two dimensional-polyacrylamide gel electrophoresis (2D-PAGE) analysis. Finally, the toxicity assays at the give concentration showed that Cu2-xSe NPs lead to non-significant toxicity as compared to control. This technology may find an advantage in fertilizer application.

Tannic Acid Capped Copper Nanoclusters as a Cost-Effective Fluorescence Probe for Hemoglobin Determination

For the first time, we report on a copper nanoclusters based fluorescence sensor for hemoglobin (Hgb). The aggregation-induced quenching of tannic acid capped copper nanoclusters' (TACuNCs) fluorescence by a Hgb-H₂O₂ mixture that mimics the Fenton's reagent is used here for the selective determination of Hgb. It is possible to effectively determine Hgb using this sensitive and cost-effective sensor in the linear range of 5.0 × 10^-8 to 4.0 × 10^-9 M with a detection limit of 5.6 × 10^-10 M. The practical utility of the sensor is evident from the good recovery values obtained from Hgb spiked with artificial blood serum.

Optoelectronic nose based on an origami paper sensor for selective detection of pesticide aerosols

This study introduces an applicable colorimetric sensor array for the detection of pesticides in the vapor phase. The array consisted of six metal nanoparticles spotted on the piece of filter paper. 3D-origami pattern was used for the fabrication of a paper-based sensor to decrease the effect of the nanoparticles leaching after exposure to analytes. Exposure to pesticide aerosols caused changes in the color of the array due to the aggregation of nanoparticles. These changes provided selective responses to thion pesticides such as malathion, parathion, chlorpyrifos, and diazinon. The sensing assay could also differentiate between aliphatic and aromatic thions and discriminate amine-containing compounds from the other studied analytes. These finding results are clearly confirmed by both visual detection and multivariate statistical methods. The proposed sensor was successfully developed for the quantitative measurement of pesticide aerosols at a very low concentration. The limit of detection of this method determined for malathion, parathion, chlorpyrifos and diazinon were 58.0, 103.0, 81.0 and 117.0, respectively. Moreover, the array could be employed to simultaneously analyze four studied pesticides. The statistcal results confirmed that the method has high performance for concurrent detection of thions as a major air pollutant without the interference of other species.

Effects of Synthetic Procedures and Postsynthesis Incubation pH on Size, Shape, and Antibacterial Activity of Copper (I) Oxide Nanoparticles

Copper (I) oxide nanoparticles (Cu2O NP) were synthesized by reducing CuSO4 with glucose in the presence of polyvinyl alcohol as a capping agent. We used three different synthetic procedures with a fast reaction (procedure 1p), a fast-then-slow reaction (procedure 2p), and a slow-then-fast reaction (procedure 3p). The reaction rates were controlled by changing the temperature and the speed of adding reagents. The synthesized Cu2O NP were subsequently incubated for 24 h in a pH 6 solution (Cu2O NP6) or a pH 8 solution (Cu2O NP8) at 5°C. XRD and SEM images analysis revealed that the 1p procedure produced smaller NP, while the 2p procedure produced larger but more uniform NP. The 3p procedure produced the largest NP with a higher size variation. The 24-hour acidic postsynthesis incubation resulted in an etching effect, which reduced the size and size variation of Cu2O NP6. To evaluate the antibacterial activity, E. coli suspensions were mixed with the obtained Cu2O NP (32, 96, or 160 ppm) for different time intervals (1 or 24 h) and then grown on Petri dishes at 37°C for 24 h. Higher doses, smaller sizes of Cu2O NP, and longer contact times with the bacterial suspension resulted in higher inactivation efficiencies. Cu2O NP6 showed higher antibacterial effects at low doses, possibly due to the etching effect and the positive surface charge. Increasing the Cu2O doses from 32 to 96 and 160 ppm noticeably increased the antibacterial effect of the Cu2O NP8, but not significantly for Cu2O NP6. We suggested that the Cu2O NP6 suffered from agglomeration at high doses due to their high surface activity and low surface charges.