Engineering noble metal nanomaterials for environmental applications

Magnetic Biochar as a Revolutionizing Approach for Diverse Dye Pollutants Elimination: A Comprehensive Review

The term "biomass" encompasses all substances found in the natural world that were once alive or derived from living organisms or their byproducts. These substances consist of organic molecules containing hydrogen, typically oxygen, frequently nitrogen, and small amounts of heavy, alkaline earth and alkali metals. Magnetic biochar refers to a type of material derived from biomass that has been magnetized typically by adding magnetic components such as magnetic iron oxides to display magnetic properties. These materials are extensively applicable in widespread areas like environmental remediation and catalysis. The magnetic properties of these compounds made them ideal for practical applications through their easy separation from a reaction mixture or environmental sample by applying a magnetic field. With the evolving global strategy focused on protecting the planet and moving towards a circular, cost-effective economy, natural compounds, and biomass have become particularly important in the field of biochemistry. The current research explores a comparative analysis of the versatility and potential of biomass for eliminating dyes as a sustainable, economical, easy, compatible, and biodegradable method. The elimination study focused on the removal of various dyes as pollutants. Various operational parameters which influenced the dye removal process were also discussed. Furthermore, the research explained, in detail, adsorption kinetic models, types of isotherms, and desorption properties of magnetic biochar adsorbents. This comprehensive review offers an advanced framework for the effective use of magnetic biochar, removing dyes from textile wastewater.

Nanoscience and nanotechnology for water remediation: an earnest hope toward sustainability

Water pollution and the global freshwater crisis are the most alarming concerns of the 21st century, as they threaten the sustainability and ecological balance of the environment. The growth of global population, climate change, and expansion of industrial processes are the main causes of these issues. Therefore, effective remediation of polluted water by means of detoxification and purification is of paramount importance. To this end, nanoscience and nanotechnology have emerged as viable options that hold tremendous potential toward the advancement of wastewater treatment methods to enhance treatment efficiency along with augmenting water supply via utilization of unconventional water sources. Materials at the nano level have shown great promise toward water treatment applications owing to their unique physicochemical properties. In this focus article, we highlight the role of new fundamental properties at the nano scale and material properties that are drastically increased due to the nano dimension (e.g. volume-surface ratio) and highlight their impact and potential toward water treatment. We identify and discuss how nano-properties could improve the three main domains of water remediation: the identification of pollutants, their adsorption and catalytic degradation. After discussing all the beneficial aspects we further discuss the key challenges associated with nanomaterials for water treatment. Looking at the current state-of-the-art, the potential as well as the challenges of nanomaterials, we believe that in the future we will see a significant impact of these materials on many water remediation strategies.

Potential New Therapies "ROS-Based" in CLL: An Innovative Paradigm in the Induction of Tumor Cell Apoptosis

Chronic lymphocytic leukemia, in spite of recent advancements, is still an incurable disease; the majority of patients eventually acquire resistance to treatment through relapses. In all subtypes of chronic lymphocytic leukemia, the disruption of normal B-cell homeostasis is thought to be mostly caused by the absence of apoptosis. Consequently, apoptosis induction is crucial to the management of this illness. Damaged biological components can accumulate as a result of the oxidation of intracellular lipids, proteins, and DNA by reactive oxygen species. It is possible that cancer cells are more susceptible to apoptosis because of their increased production of reactive oxygen species. An excess of reactive oxygen species can lead to oxidative stress, which can harm biological elements like DNA and trigger apoptotic pathways that cause planned cell death. In order to upset the balance of oxidative stress in cells, recent therapeutic treatments in chronic lymphocytic leukemia have focused on either producing reactive oxygen species or inhibiting it. Examples include targets created in the field of nanomedicine, natural extracts and nutraceuticals, tailored therapy using biomarkers, and metabolic targets. Current developments in the complex connection between apoptosis, particularly ferroptosis and its involvement in epigenomics and alterations, have created a new paradigm.

Use of biomass-derived biochar in wastewater treatment and power production: A promising solution for a sustainable environment

Over the past few years, we are witnessing the advent of a revolutionary bioengineering technology in biochar production and its application in waste treatment and an important component in power generation devices. Biochar is a solid product, highly rich in carbon, whose adsorption properties are ideal for wastewater decontamination. Due to its high specific surface area to volume ratio, it can be utilized for many environmental applications. It has diverse applications in various fields. This review focuses on its various applications in wastewater treatment to remove various pollutants such as heavy metals, dyes, organic compounds, and pesticides. This review also highlights several energy-based applications in batteries, supercapacitors, and microbial fuel cells. It described information about the different feedstock materials to produce LB-derived biochar, the various conditions for the production process, i.e., pyrolysis and the modification methods of biochar for improving properties required for wastewater treatment. The present review helps the readers understand the importance of biochar in wastewater treatment and its application in power generation in terms of batteries, supercapacitors, microbial fuel cells, applications in fuel production, pollutant and dye removal, particularly the latest development on using LB-derived biochar. This review also highlights the economic and environmental sustainability along with the commercialization of biochar plants. It also describes various pyrolytic reactors utilized for biochar production.

Toward continuous production of high-quality nanomaterials using microfluidics: nanoengineering the shape, structure and chemical composition

Over the last decade, a multitude of synthesis strategies has been reported for the production of high-quality nanoparticles. Wet-chemical methods are generally the most efficient synthesis procedures since high control of crystallinity and physicochemical properties can be achieved. However, a number of challenges remain from inadequate reaction control during the nanocrystallization process; specifically variability, selectivity, scalability and safety. These shortcomings complicate the synthesis, make it difficult to obtain a uniform product with desired properties, and present serious limitations for scaling the production of colloidal nanocrystals from academic studies to industrial applications. Continuous flow reactors based on microfluidic principles offer potential solutions and advantages. The reproducibility of reaction conditions in microfluidics and therefore product quality have proved to exceed those obtained by batch processing. Considering that in nanoparticles' production not only is it crucial to control the particle size distribution, but also the shape and chemical composition, this review presents an overview of the current state-of-the-art in synthesis of anisotropic and faceted nanostructures by using microfluidics techniques. The review surveys the available tools that enable shape and chemical control, including secondary growth methods, active segmented flow, and photoinduced shape conversion. In addition, emphasis is placed on the available approaches developed to tune the structure and chemical composition of nanomaterials in order to produce complex heterostructures in a continuous and reproducible fashion.

Gold Cluster Capped with a BCL-2 Antagonistic Peptide Exerts Synergistic Antitumor Activity in Chronic Lymphocytic Leukemia Cells

Chronic lymphocytic leukemia (CLL) is still incurable by conventional chemotherapy due to the resistance to apoptosis. We have previously found that a peptide-capped gold cluster (Au₂₅Sv₉) can target on the aberrant oxidative stress in CLL cells to specially inhibit thioredoxin reductase (TrxR) activity, resulting in significant apoptosis. However, the required doses of the gold cluster for inducing apoptosis are high, restricting its potential for further applications. Notably, the most recent studies suggested that CLL cells overexpressed antiapoptotic BCL-2 protein to prevent chemotherapy-induced apoptosis, indicating that BCL-2 could be a promising target for CLL therapy. Regrettably, the nonmitochondrial-targeted Au₂₅Sv₉ has little effect on BCL-2. In this study, we successfully screened a modified BADBH3 peptide (B1P) that could antagonize BCL-2 protein in CLL cells. We found that B1P could effectively sensitize MEC-1 cells to a subliminal dose of Au₂₅Sv₉. To simplify the treatment regimen, we directly fabricated a gold cluster capped with the B1P peptides by one-step synthesis to integrate the BCL-2 antagonistic activity into the gold the cluster, named BGC. We already found that low doses of BGC could significantly induce more apoptosis in MEC-1 cells than equivalent doses of the Au₂₅Sv₉ cluster or B1P peptide alone. Mechanistically, in addition to the inherent inhibitory effect of gold clusters on TrxR activity, BGC could bind to BCL-2 on mitochondria and activate the BCL-2 family-mediated mitochondrial apoptosis cascade more effectively. These results demonstrated that antagonizing the overexpressed BCL-2 in CLL cells, together with inhibiting TrxR simultaneously by a single gold cluster, is a promising strategy for the treatment of CLL cells. This study will provide a paradigm and reference for the development of functionalized gold clusters with rationally designed peptides, and opens up a new opportunity for the treatment of CLL in clinical settings.

Presence of fluoride in water diminishes fast the SPR peak of silver nanocrystals showing large red shift with quick sedimentation - A fast sensing and fast removal case

The medicinal use of fluoride is beneficial up to a low ppm level but regular ingestion at high doses show many adverse effects in human. Fluoride may get ingested through drinking water specially through ground water near the hilly regions, where fluoride content is huge. Hence, fluoride sensing and removal of it from water is very important as fluoride contaminated water is transparent and not easily detectable. Here, we have studied colorimetric and spectrophotometric techniques for sensing of fluoride along with its fast removal from water by using prepared saponin capped silver nanoparticles (AgNPs). Colorimetric study has confirmed the presence of fluoride ions in water samples above the colorimetric detection limit of 10 ppm. But spectroscopic sensing further provides more lower limit of sensing with the total removal of fluoride ions up to 1.2 ppm level. On repeating this this study 15 times, sensing and removal of fluoride is found to be well reproducible. The interaction of fluoride ions with silver nanoparticles has resulted in sedimentation of fluoride ions in the form of fluoride-nanoparticles complex and that interaction has been confirmed by FTIR spectral study of the sedimented part. EDX analysis has also provided the information of easy removal of the fluoride ions from water as presence of fluoride peak has been found in EDX spectra.

MnO2 -Based Materials for Environmental Applications

Manganese dioxide (MnO₂ ) is a promising photo-thermo-electric-responsive semiconductor material for environmental applications, owing to its various favorable properties. However, the unsatisfactory environmental purification efficiency of this material has limited its further applications. Fortunately, in the last few years, significant efforts have been undertaken for improving the environmental purification efficiency of this material and understanding its underlying mechanism. Here, the aim is to summarize the recent experimental and computational research progress in the modification of MnO₂ single species by morphology control, structure construction, facet engineering, and element doping. Moreover, the design and fabrication of MnO₂ -based composites via the construction of homojunctions and MnO₂ /semiconductor/conductor binary/ternary heterojunctions is discussed. Their applications in environmental purification systems, either as an adsorbent material for removing heavy metals, dyes, and microwave (MW) pollution, or as a thermal catalyst, photocatalyst, and electrocatalyst for the degradation of pollutants (water and gas, organic and inorganic) are also highlighted. Finally, the research gaps are summarized and a perspective on the challenges and the direction of future research in nanostructured MnO₂ -based materials in the field of environmental applications is presented. Therefore, basic guidance for rational design and fabrication of high-efficiency MnO₂ -based materials for comprehensive environmental applications is provided.

Mechanistic insights into the two-phase synthesis of heteroleptic Au nanoclusters

A mechanistic study on the two-phase synthesis of heteroleptic Au nanoclusters (NCs) is reported here. First, the effects of binary ligands on controlling the size of Au NCs were examined: (1) the binary ligands could exhibit an eclectic effect on the size control of Au NCs if the binding affinities of such hetero-ligands with Au are comparable and (2) the binary ligands could exhibit a competitive effect on the size control of Au NCs, and the size of the Au NCs could be determined by the ligand with stronger binding affinity to Au. This finding is interesting and can shed some light on the design of new functional metal NCs. Secondly, the formation mechanism of the heteroleptic Au NCs that originated from the complex precursors was unprecedentedly studied. The complex precursors of the heteroleptic Au NCs were identified to be the predominant hybridized ligand_#1-Au(i)-ligand_#2 species, which is helpful for understanding the synthetic mechanisms in depth. Moreover, the growth processes of the heteroleptic Au NCs were also monitored, and some fundamental perceptions about the growth pathway and the structures of the Au NCs were obtained.

Rapid Detection of Hepatitis B Virus in Blood Samples Using a Combination of Polymerase Spiral Reaction With Nanoparticles Lateral-Flow Biosensor

A rapid, highly sensitive, and robust diagnostic technique for point-of-care (PoC) testing can be developed using the combination of the nanoparticle-based lateral flow biosensors (LFB) and isothermal nucleic acid amplification technology. Here, we developed a polymerase spiral reaction (PSR) containing FITC-labeled DNA probes coupled with the nanoparticle-based LFB assay (PSR-LFB) to detect the amplified products to detect HBV visually. Under the optimized conditions, the PSR assay involved incubation of the reaction mixture for 20 min at 63°C, followed by visual detection of positive amplicons using LFB, which would generate a red test line based on the biotin/streptavidin interaction and immunoreactions, within 5 min. A cross-reactivity test revealed that the developed PSR-LFB assay showed good specificity for HBV and could distinguish HBV from other pathogenic microorganisms. For the analytical sensitivity, the limit of detection (LoD) of PSR-LFB assay was recorded as 5.4 copies/mL of HBV genomic DNA, which was ten-times more sensitive than qPCR and loop-mediated isothermal amplification (LAMP). Additionally, all the HBV-positive (29/82) samples, identified using ELISA, were also successfully detected by the PSR-LFB assay. We found that the true positive rate of the PSR-LFB assay was higher than that of qPCR (100 vs. 89.66%, respectively), as well as the LAMP assay (100 vs. 96.55%, respectively). Furthermore, the integrated procedure could be completed in 60 min, including the processing of the blood samples (30 min), an isothermal reaction (20 min), and result visualization (5 min). Thus, this PSR-LFB assay could be a potentially useful technique for PoC diagnosis of HBV in resource-limited countries.

Novel mesoporous Ag@SiO2 nanospheres as a heterogeneous catalyst with superior catalytic performance for hydrogenation of aromatic nitro compounds

Mesoporous core–shell structure Ag@SiO₂ nanospheres are constructed to prevent Ag nanoparticles from aggregation during the hydrogenation reaction. The prepared catalyst shows superior catalytic performance for hydrogenation of nitro compounds with 100% conversion and selectivity without any by-products, which also indicates good recycling performance for several times use.

Mesoporous core–shell structure Ag@SiO₂ nanospheres are constructed to prevent Ag nanoparticles from aggregation during the hydrogenation reaction.

Laser-Based Synthesis of Au Nanoparticles for Optical Sensing of Glyphosate: A Preliminary Study

Nowadays, gold nanoparticles Au nanoparticles (AuNPs) capture great interest due to their chemical stability, optical properties and biocompatibility. The success of technologies based on the use of AuNPs implies the development of simple synthesis methods allowing, also, the fine control over their properties (shape, sizes, structure). Here, we present the AuNPs fabrication by nanosecond pulsed laser ablation in citrate-solution, that has the advantage of being a simple, economic and eco-sustainable method to fabricate colloidal solutions of NPs. We characterized the stability and the absorbance of the solutions by Ultraviolet-Visible (UV-Vis) spectroscopy and the morphology of the AuNPs by Transmission Electron Microscopy. In addition, we used the AuNPs solutions as colorimetric sensor to detect the amount of glyphosate in liquid. Indeed, glyphosate is one of the most widely used herbicides which intensive use represents a risk to human health. The glyphosate presence in the colloidal AuNPs solutions determines the aggregation of the AuNPs causing the change in the color of the solution. The variation of the optical properties of the colloidal solutions versus the concentration of glyphosate is studied.

Pd on poly(1-vinylimidazole) decorated magnetic S-doped grafitic carbon nitride: an efficient catalyst for catalytic reduction of organic dyes

A novel magnetic catalyst, (SGCN/Fe₃O₄/PVIs/Pd) was synthesized by growing of poly(1-vinylimidazole) on the surface of ionic liquid decorated magnetic S-doped graphitic carbon nitride, followed by stabilization of palladium nanoparticles. Catalytic activity of the prepared heterogeneous catalyst was explored for the catalytic reduction of hazardous dyes, methyl orange and Rhodamine B, in the presence of NaBH₄. Besides, the effects of the reaction variables on the catalytic activity were investigated in detail. The kinetics study established that dye reduction was the first order reaction and the apparent activation energy was calculated to be 72.63 kJ/mol and 68.35 kJ/mol¹ for methyl orange and Rhodamine B dyes, respectively. Moreover, ΔS^# and ΔH^# values for methyl orange were found to be − 33.67 J/mol K and 68.39 kJ/mol respectively. These values for Rhodamine B were − 45.62 J/mol K and 65.92 kJ/mol. The recycling test verified that the catalyst possessed good stability and reusability, thereby making it a good candidate for the catalytic purposes. Furthermore, a possible catalytic mechanism for dye catalytic reduction over SGCN/Fe₃O₄/PVIs/Pd was proposed.

From Monolayer-Protected Gold Cluster to Monolayer-Protected Gold-Sulfide Cluster: Geometrical and Electronic Structure Evolutions of Au60S n (SR)36 (n = 0-12)

Thiolate-monolayer-protected gold clusters are usually formulated as AuNSR[Au(I)-SR] x , where AuN and SR[Au(I)-SR] x (x = 0, 1, 2, ...) are the inner gold core and outer protection motifs, respectively. In this work, we theoretically envision a new family of S-atom-doped thiolate-monolayer-protected gold clusters, namely, Au60S n (SR)36 (n = 0-12). A distinct feature of Au60S n (SR)36 nanoclusters (NCs) is that they show a gradual transition from the monolayer-protected metal NC to the SR[Au(I)-(SR)] x oligomer-protected gold-sulfide cluster with the increase of the number of doping S atoms. The possible formation mechanism of the S-atom-doped thiolate-protected gold cluster is investigated, and the size-dependent stability and electronic and optical absorption properties of Au60S n (SR)36 are explored using density functional theory (DFT) calculations. It is found that doping of S atom significantly tails the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap and optical absorption properties of thiolate-protected gold cluster, representing a promising way to fabricate new monolayer-protected gold nanoparticles.

Protein-stabilized gold nanoclusters for PDT: ROS and singlet oxygen generation

Suitable properties as well as eco-friendly synthesis of photoluminescent Au nanoclusters (NCs) make them promising compounds for biomedical diagnostics and visualization applications. However, the potential photochemical activity of such agents on cancerous cells is largely unknown. The nanoclusters (BSA-Au NCs) were synthetized in the presence of BSA (an average hydrodynamic diameter was about 9.4 nm, while the size of the metal cluster was <1.3 nm according to atomic force microscopy measurements) and possessed a broad photoluminescence band at 680 nm in buffered (pH 7.2) aqueous medium. The photochemical activity was studied by adding two fluorescent probes (dihydrorhodamine or Singlet Oxygen Sensor Green) for detection of reactive oxygen species in samples irradiated at 405 nm to minimize direct excitation of the probes. The photoluminescence measurements evidenced the capability of BSA-Au NCs to generate reactive oxygen species upon light exposure, while the observed sensitivity of the photoluminescence properties might be used to indicate photooxidative processes in the medium. The viability test performed on breast cancer cells after incubation with BSA-Au NCs and subsequent irradiation revealed notable difference in induced phototoxicity between two cell lines, which was not the case after the corresponding treatment using the photosensitizer chlorin e₆.

Opportunities and challenges in energy and electron transfer of nanocluster based hybrid materials and their sensing applications

This feature article highlights the recent advances of luminescent metal nanoclusters (MNCs) for their potential applications in healthcare and energy-related materials because of their high photosensitivity, thermal stability, low toxicity, and biocompatibility.

Water-soluble metal nanoclusters: recent advances in molecular-level exploration and biomedical applications

Recent advances of water-soluble metal nanoclusters (MNCs) in designing highly luminescent MNCs, ligand shell engineering, tracking MNC's growth processes, and biomedical applications are highlighted.

A Novel Self-Assembled Mitochondria-Targeting Protein Nanoparticle Acting as Theranostic Platform for Cancer

Self-assembled protein nanoparticles have attracted much attention in biomedicine because of their biocompatibility and biodegradability. Protein nanoparticles have become widely utilized as diagnostic or therapeutic agents for various cancers. However, there are no reports that protein nanoparticles can specifically target mitochondria. This targeting is desirable, since mitochondria are critical in the development of cancer cells. In this study, the discovery of a novel self-assembled metal protein nanoparticle, designated GST-MT-3, is reported, which targets the mitochondria of cancer cells within 30 min in vitro and rapidly accumulates in tumors within 1 h in vivo. The nanoparticles chelate cobalt ions [GST-MT-3(Co²⁺ )], which induces reactive oxygen species (ROS) production and reduces the mitochondrial membrane potential. These effects lead to antitumor activity in vivo. GST-MT-3(Co²⁺ ) with covalently conjugated paclitaxel synergistically suppress tumors and prolong survival. Importantly, the effective dosage of paclitaxel is 50-fold lower than that utilized in standard chemotherapy (0.2 vs 10 mg kg^-1 ). To the best of the authors' knowledge, GST-MT-3 is the first reported protein nanoparticle that targets mitochondria. It has the potential to be an excellent platform for combination therapies.

Comparative biological effects of spherical noble metal nanoparticles (Rh, Pd, Ag, Pt, Au) with 4-8 nm diameter

For a comparative cytotoxicity study, nanoparticles of the noble metals Rh, Pd, Ag, Pt, and Au (spherical, average diameter 4 to 8 nm) were prepared by reduction in water and colloidally stabilized with poly(N-vinyl pyrrolidone) (PVP). Thus, their shape, size, and surface functionalization were all the same. Size and morphology of the nanoparticles were determined by dynamic light scattering (DLS), analytical disc centrifugation (differential centrifugal sedimentation, DCS), and high-resolution transmission electron microscopy (HRTEM). Cell-biological experiments were performed to determine the effect of particle exposure on the viability of human mesenchymal stem cells (hMSCs). Except for silver, no adverse effect of any of the metal nanoparticles was observed for concentrations up to 50 ppm (50 mg L-1) incubated for 24 h, indicating that noble metal nanoparticles (rhodium, palladium, platinum, gold) that do not release ions are not cytotoxic under these conditions.

LSPR Tuning from 470 to 800 nm and Improved Stability of Au-Ag Nanoparticles Formed by Gold Deposition and Rebuilding in the Presence of Poly(styrenesulfonate)

Stability and precise control over functional properties of metal nanoparticles remain a challenge for the realization of prospective applications. Our described process of shell formation and rebuilding can address both these challenges. Template silver nanoparticles (AgNPs) stabilized by poly(styrenesulfonate) are first transformed with gold deposition, after which the resulting shell rebuilds with the replaced silver. The shell formation and rebuilding are accompanied by large shifts in localized surface plasmon resonance (LSPR) peak position, which enables LSPR tuning in a range from 470 to 800 nm. Furthermore, chemical stability of Au-AgNPs is significantly improved compared to AgNPs due to gold stability. Silver templates of different shapes and sizes were demonstrated to transform to AuAg composite NPs to further extend the accessible LSPR range tuning. Stabilization of template AgNPs with poly(styrenesulfonate), in contrast to commonly used poly(vinylpyrrolidone), was found to be a key factor for shell rebuilding. The developed Au-AgNPs were shown to be advantageous for surface plasmon resonance (SPR) detection and surface-enhanced Raman spectroscopy (SERS) owing to their tunable LSPR and enhanced stability.

Influence of Poly(vinylpyrrolidone) concentration on properties of silver nanoparticles manufactured by modified thermal treatment method

Very narrow and pure silver nanoparticles were synthesized by modified thermal treatment method via oxygen and nitrogen flow in succession. The structural and optical properties of the calcined silver nanoparticles at 600°C with diverse Poly(vinylpyrrolidone) concentrations varied from 2% to 4% were studied by means of different techniques. Fourier transform infrared spectroscopy was used to monitor the production of pure Ag nanoparticles at a given Poly(vinylpyrrolidone) concentration. The X-ray powder diffraction spectra are evidence for the transformation of the amorphous sample at 30°C to the cubic crystalline nanostructures at the calcination temperatures for all Poly(vinylpyrrolidone) concentrations. The transmission electron microscopy images showed the creation of spherical silver nanoparticles with the average particle size decreased by increasing Poly(vinylpyrrolidone) concentrations from 4.61 nm at 2% to 2.49 nm at 4% Poly(vinylpyrrolidone). The optical properties were investigated by means of UV-vis absorption spectrophotometer, which showed an increase in the conduction band of Ag nanoparticles with increasing Poly(vinylpyrrolidone) concentrations from 2.83 eV at 2% Poly(vinylpyrrolidone) to 2.94 eV at 4% Poly(vinylpyrrolidone) due to decreasing particle size. This was due to less attraction between conduction electrons and metal ions for smaller particle size corresponding to fewer atoms that made up the metal nanoparticles.

Surface Decoration of Pt Nanoparticles via ALD with TiO2 Protective Layer on Polymeric Nanofibers as Flexible and Reusable Heterogeneous Nanocatalysts

Coupling the functional nanoheterostructures over the flexible polymeric nanofibrous membranes through electrospinning followed by the atomic layer deposition (ALD), here we presented a high surface area platform as flexible and reusable heterogeneous nanocatalysts. Here, we show the ALD of titanium dioxide (TiO₂) protective nanolayer onto the electrospun polyacrylonitrile (PAN) nanofibrous web and then platinum nanoparticles (Pt-NP) decoration was performed by ALD onto TiO₂ coated PAN nanofibers. The free-standing and flexible Pt-NP/TiO₂-PAN nanofibrous web showed the enhancive reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) within 45 seconds though the hydrogenation process with the degradation rate of 0.1102 s⁻¹. The TiO₂ protective layer on the PAN polymeric nanofibers was presented as an effective route to enhance the attachment of Pt-NP and to improve the structure stability of polymeric nanofibrous substrate. Commendable enhancement in the catalytic activity with the catalytic dosage and the durability after the reusing cycles were investigated over the reduction of 4-NP. Even after multiple usage, the Pt-NP/TiO₂-PAN nanofibrous webs were stable with the flexible nature with the presence of Pt and TiO₂ on its surface.

Fabricating chiroptical starfruit-like Au nanoparticles via interface modulation of chiral thiols

The surface/interface matters as the size of materials enters the nanoscale. Control of surface/interface, therefore, plays an important role in creating novel nanostructures with unusual properties and in obtaining devices with high performance. Herein, we demonstrate unique interface regulation in fabricating nanostructures with strong plasmonic circular dichroism (PCD). With chiral cysteine (Cys) as surface-modulating molecules, starfruit-like Au nanoparticles (NPs) with high PCD responses are obtained via Au overgrowth on Au nanorods (AuNRs). Pre-incubation of the AuNRs with Cys is vital in achieving strong and reproducible PCD responses. Instead of contributing to PCD signals, the pre-adsorbed Cys molecules are found to play a major role in manipulating the Au growth mode and thus the formation of hotspots within the shell. Strong PCD signal mainly comes from the entrapped Cys molecules within the hotspots and is enhanced via local field effect. The distinct roles of the same ligands at different surfaces/interfaces are elucidated. Furthermore, our findings contribute to the strategy of utilizing interface modulation to fabricate complex nanostructures with novel properties.

Directional growth of Ag nanorod from polymeric silver cyanide: A potential substrate for concentration dependent SERS signal enhancement leading to melamine detection

Attention has been directed to prepare exclusive one-dimensional silver nanostructure from the linear inorganic polymer AgCN. Successive color change from yellow to orange, to red and finally to green reflects the evolution of high yielding Ag nanorods (NRs) from well-known -[Ag-CN]- chains of polymeric AgCN at room temperature. The parental 1D morphology of AgCN is retained within the as-synthesized Ag NRs. So we could successfully exploit the Ag NR for surface-enhanced Raman scattering (SERS) studies for sensing a popular milk adulterant melamine down to picomolar level. We observed interesting concentration dependent selective SERS band enhancement of melamine. The enhanced ~1327cm^-1 SERS signal intensity at lower concentration (10^-9 and 10^-12M) of melamine speaks for the preferential participation of -C-N of melamine molecule with Ag surface. On the other hand, '-NH₂' group together with ring 'N' participation of melamine molecule onto Ag surface suggested an adsorptive stance at higher (10^-3-10^-7M) concentration range. Thus the binding modes of the molecule at the Ag surface justify its fluxional behavior.

Size-Controlled Pd Nanoparticle Catalysts Prepared by Galvanic Displacement into a Porous Si-Iron Oxide Nanoparticle Host

Porous silicon nanoparticles containing both Pd and iron oxide nanoparticles are prepared and studied as magnetically recoverable catalysts for organic reductions. The Pd nanoparticles are generated in situ by electroless deposition of Pd(NH₃)₄²⁺, where the porous Si skeleton acts as both a template and as a reducing agent and the released ammonia ligands raise the local pH to exert control over the size of the Pd nanoparticles. The nanocomposites are characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, nitrogen adsorption, X-ray diffraction, superconducting quantum interference device magnetization, and dynamic light scattering. The nanocomposite consists of a porous Si nanoparticle (150 nm mean diameter) containing ∼20 nm pores, uniformly decorated with a high loading of surfactant-free Pd nanoparticles (12 nm mean diameter) and superparamagnetic γ-Fe₂O₃ nanoparticles (∼7 nm mean diameter). The reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride is catalyzed by the nanocomposite, which is stable through the course of the reaction. Catalytic reduction of the organic dyes methylene blue and rhodamine B is also demonstrated. The conversion efficiency and catalytic activity are found to be superior to a commercial Pd/C catalyst compared under comparable reaction conditions. The composite catalyst can be recovered from the reaction mixture by applying an external magnetic field due to the existence of the superparamagnetic iron oxide nanoparticles in the construct. The recovered particles retain their catalytic activity.

Ultrasensitive room-temperature ethanol detection based on Au functionalized nanoporous SnO2/C60/SnO2 composites

An Au functionalized nanoporous SnO₂/C₆₀/SnO₂ gas sensor exhibits an extremely sensitive, selective sub-ppm level ethanol gas detection at room temperature.

Hybrid Plasmonic Nanostructures

Plasmonic hybrid nanostructure including Semiconductor-metallic nanoparticles, and graphene-plasmonic nanocomposites have great potential to be used as photocatalyst for hydrogen production and for photodegradation of organic waste. Also, they are potential candidate as active materials in photovoltaic devices. Plasmonic-magnetic nanocomposites could be used in photothermal therapy and biomedical imaging. This chapter will focus on the environmental impact of these materials and their in-vitro and in-vivo toxicity. In addition, the applications of these hybrid nanostructures in energy and environment will be discussed in details.

Fucoidan-coated core–shell magnetic mesoporous silica nanoparticles for chemotherapy and magnetic hyperthermia-based thermal therapy applications

Fucoidan-coated FeNP@SiOH@Fuc NPs have been proposed for chemotherapy and thermal therapy applications in emerging cancer therapy.