Synthesis of Au, Ag, and Au-Ag Bimetallic Nanoparticles Using Pulicaria undulata Extract and Their Catalytic Activity for the Reduction of 4-Nitrophenol

Morphology and optical properties of Au-Ag hybrid nanoparticles regulation and its ultra-sensitive SERS immunoassay detection in carbohydrate antigen 19-9

The development of an ultra-sensitive detection method for carbohydrate antigen 19-9 (CA19-9) is very important for the early diagnosis of pancreatic cancer. In this work, we developed a new strategy to achieve a variety of Au-Ag hybrid nanoparticles from janus to core-satellite which is controlled by the volume of AgNO3 and the concentration of benzimidazolecarboxylic acid (MBIA). With the volume of AgNO3 increased, Au-Ag hybrid nanoparticles changed from janus to core-satellite and the characteristic absorption peak showed two opposite trends. The size and number of Ag islands were determined by the concentration of MBIA. Au-Ag core-satellites nanoparticles with a large number of small-sized Ag have the highest SERS intensity. Then we used them as SERS nanotags and Au-Polystyrene nanospheres modified by captured anti-CA19-9 antibody as solid substrates to realize the ultra-sensitive detection of CA19-9 with a low limit of detection of 1.25 × 10-6 IU/mL and a wide linear range of 1.00 × 10-5 -1.00 × 104 IU/mL. This work not only demonstrates that MBIA and AgNO3 were the key factors in the growth of Au-Ag hybrid nanoparticles from 2D to 3D structure but also supplies an ultra-sensitive detection method for CA19-9 which has a potential practicability in the clinical early diagnoses of pancreatic cancer.

Innovating Leishmaniasis Treatment: A Critical Chemist's Review of Inorganic Nanomaterials

Leishmaniasis, a critical Neglected Tropical Disease caused by Leishmania protozoa, represents a significant global health risk, particularly in resource-limited regions. Conventional treatments are effective but suffer from serious limitations, such as toxicity, prolonged treatment courses, and rising drug resistance. Herein, we highlight the potential of inorganic nanomaterials as an innovative approach to enhance Leishmaniasis therapy, aligning with the One Health concept by considering these treatments' environmental, veterinary, and public health impacts. By leveraging the adjustable properties of these nanomaterials─including size, shape, and surface charge, tailored treatments for various diseases can be developed that are less harmful to the environment and nontarget species. We review recent advances in metal-, oxide-, and carbon-based nanomaterials for combating Leishmaniasis, examining their mechanisms of action and their dual use as standalone treatments or drug delivery systems. Our analysis highlights a promising yet underexplored frontier in employing these materials for more holistic and effective disease management.

Nanoengineering of mono (Au, Ag) and bimetallic (Ag-Au) alloy nanoparticles for dye degradation and toxicity assessment

This research entails the synthesis and catalytic exploration of bimetallic nanoparticles combining silver (Ag) and gold (Au). The Au concentration was systematically varied (20%, 40%, 60%, and 80%), alongside the utilization of CTAB surfactant for nanoparticle stabilization. UV visible spectroscopic analysis confirmed the formation and stability of synthesized Au, Ag and bimetallic (Ag-Au) nanoparticles. FESEM further confirmed the formation of uniform sized Au and Ag nanoparticles. Integration of Au into Ag resulted in bimetallic (Ag-Au) alloy nanoparticles with smaller dimensions as compared to individual Au and Ag nanoparticles. EDX spectra and mapping verified the composition of each synthesized bimetallic nanoparticle variant. The catalytic potential of the synthesized nanoparticles was methodically explored using UV-visible spectroscopy. All the synthesized nanoparticles showcased excellent catalytic efficacy. The synergistic effect of the alloyed bimetallic nanoparticles was found promising. Assessment of dye toxicity pre- and post-degradation was conducted using the ECOSAR program, indicating a reduction in dye toxicity following degradation.

Exploring the Potential of Endophytic Microorganisms and Nanoparticles for Enhanced Water Remediation

Endophytic microorganisms contribute significantly to water bioremediation by enhancing pollutant degradation and supporting aquatic plant health and resilience by releasing bioactive compounds and enzymes. These microorganisms inhabit plant tissues without causing disease or any noticeable symptoms. Endophytes effectively aid in eliminating contaminants from water systems. Nanoparticles serve as potent enhancers in bioremediation processes, augmenting the efficiency of pollutant degradation by increasing surface area and bioavailability, thereby improving the efficacy and rate of remediation. Their controlled nutrient release and ability to stabilize endophytic colonization further contribute to the enhanced and sustainable elimination of contaminated environments. The synergistic effect of endophytes and nanoparticles in water remediation has been widely explored in recent studies, revealing compelling outcomes. Water pollution poses significant threats to human health, ecosystems, and economies; hence, the sixth global goal of the Sustainable Development Agenda 2030 of the United Nations aims to ensure the availability and sustainable management of water resources, recognizing their crucial importance for current and future generations. Conventional methods for addressing water pollution exhibit several limitations, including high costs, energy-intensive processes, the production of hazardous by-products, and insufficient effectiveness in mitigating emerging pollutants such as pharmaceuticals and microplastics. Noticeably, there is an inability to effectively remove various types of pollutants, thus resulting in incomplete purification cycles. Nanoparticle-enhanced water bioremediation offers an innovative, eco-friendly alternative for degrading contaminants. A growing body of research has shown that integrating endophytic microorganisms with nanoparticles for water bioremediation is a potent and viable alternative. This review examines the potential of using endophytic microorganisms and nanoparticles to enhance water remediation, exploring their combined effects and applications in water purification. The paper also provides an overview of synthetic methods for producing endophyte-nanoparticle composites to optimize their remediation capabilities in aqueous environments. The final section of the review highlights the constraints related to integrating endophytes with nanoparticles.

Application of Surface-Enhanced Raman Spectroscopy Combined with Immunoassay for the Detection of Adrenoceptor Agonists

Rapid, sensitive, and accurate detection of adrenoceptor agonists is a significant research topic in the fields of food safety and public health. Immunoassays are among the most widely used methods for detecting adrenoceptor agonists. In recent years, surface-enhanced Raman spectroscopy combined with immunoassay (SERS-IA) has become an effective technique for improving detection sensitivity. This review focuses on the innovation of Raman reporter molecules and substrate materials for the SERS-IA of adrenoceptor agonists. In addition, it also investigates the challenges involved in potentially applying SERS-IA in the detection of adrenoceptor agonists. Overall, this review provides insight into the design and application of SERS-IA for the detection of adrenoceptor agonists, which is critical for animal-derived food safety and public health.

Determination of Photothermal and EMI Shielding Efficiency of Graphene-Silver Nanoparticle Composites Prepared under Low-Dose Gamma Irradiation

Silver nanoparticles (Ag NPs) have been produced by low-dose (1-20 kGy) gamma irradiation of silver nitrate in the presence of graphene-based material (graphene oxide or electrochemically exfoliated graphene). The large surface area of those graphene-based materials combined with the presence of oxygen-containing functional groups on the surface provided successful nucleation and growth of Ag nanoparticles, which resulted in a uniformly covered graphene surface. The obtained Ag nanoparticles were spherical with a predominant size distribution of 10-50 nm for graphene oxide and 10-100 nm for electrochemically exfoliated graphene. The photothermal efficiency measurement showed a temperature increase upon exposure to a 532 nm laser for all samples and the highest photothermal efficiency was measured for the graphene oxide/Ag NP sample prepared at 5 kGy. Electromagnetic interference (EMI) shielding efficiency measurements showed poor shielding for the composites prepared with graphene oxide. On the other hand, all composites prepared with electrochemically exfoliated graphene showed EMI shielding to some extent, and the best performance was measured for the samples prepared at 5 and 20 kGy doses.

Restoration of Antibacterial Activity of Inactive Antibiotics via Combined Treatment with AgNPs

Antimicrobial resistance poses a huge threat to human health around the world and calls for novel treatments. Combined formulations of NPs and antibiotics have emerged as a viable nanoplatform for combating bacterial resistance. The present research work was performed to investigate the effect of combined formulations of AgNPs with streptomycin, cefaclor, ciprofloxacin, and trimethoprim against multidrug-resistant (MDR) isolates of Staphylococcus aureus and Klebsiella pneumoniae. AgNPs have been synthesized by using the Nigella sativa seed extract, and their characteristics were analyzed. AgNPs depicted concentration-dependent antibacterial effects, as the highest concentration of AgNPs showed the strongest antibacterial activity. Interestingly, AgNPs in conjugation with antibiotics showed an enhanced antibacterial potential against both S. aureus and K. pneumoniae, which suggested synergism between the AgNPs and antibiotics. Against S. aureus, streptomycin and trimethoprim in conjugation with AgNPs presented a synergistic effect, while cefaclor and ciprofloxacin in combination with AgNPs showed an additive effect. However, all of the tested antibiotics depicted a synergistic effect against K. pneumoniae. The lowest value of MIC (0.78 μg/mL) was shown by AgNPs-Stp against S. aureus, whereas AgNPs-Tmp showed the lowest value of MIC (1.56 μg/mL) against K. pneumoniae. The most important point of the present study is that both organisms (S. aureus and K. pneumoniae) showed resistance to antibiotics but turned out to be highly susceptible when the same antibiotic was used in combination with AgNPs. These findings highlight the potential of nanoconjugates (the AgNPs-antibiotic complex) to mitigate the present-day crisis of antibiotic resistance and to combat antimicrobial infections efficiently.

Fast synthesis of nanoporous Cu/Ag bimetallic triangular nanoprisms via galvanic replacement for efficient 4-nitrophenol reduction

We report the synthesis of nanoporous Cu/Ag bimetallic triangular nanoprisms (BTNPs) using a galvanic replacement method. Based on ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS), selected area electron diffraction (SAED) and X-ray photoelectron spectroscopy (XPS) analyses, the structure of Cu/Ag BTNPs was characterized. The prepared Cu/Ag BTNPs exhibited excellent catalytic activity and good cycling stability for the reduction of 4-nitrophenol (4-NP) due to the synergistic effect between Cu and Ag elements. The kinetic rate constant (k) and turnover frequency (TOF) values reached 331 × 10-3 s-1 and 500 × 10-3 s-1, respectively, which were higher than those of previously reported Cu, Ag, Au, Cu/Ag or Cu/Au-based catalysts. We hope that the development of promising routes for high-quality BTNPs can broaden their applications in catalysis and environmental sustainability.

A review of physical, chemical and biological synthesis methods of bimetallic nanoparticles and applications in sensing, water treatment, biomedicine, catalysis and hydrogen storage

This article provides an in-depth analysis of various fabrication methods of bimetallic nanoparticles (BNP), including chemical, biological, and physical techniques. The review explores BNP's diverse uses, from well-known applications such as sensing water treatment and biomedical uses to less-studied areas like breath sensing for diabetes monitoring and hydrogen storage. It cites results from over 1000 researchers worldwide and >300 peer-reviewed articles. Additionally, the article discusses current trends, actionable recommendations, and the importance of synthetic analysis for industry players looking to optimize manufacturing techniques for specific applications. The article also evaluates the pros and cons of various fabrication methods, highlighting the potential of plant extract synthesis for mass production of capped BNPs. However, it warns that this method may not be suitable for certain applications requiring ligand-free surfaces. In contrast, physical methods like laser ablation offer better control and reactivity, especially for applications where ligand-free surfaces are critical. The report underscores the environmental benefits of plant extract synthesis compared to chemical methods that use hazardous chemicals and pose risks to extraction, production, and disposal. The article emphasizes the need for life cycle assessment (LCA) articles in the literature, given the growing volume of research on nanotechnology materials. This article caters to researchers at all stages and applies to various fields applying nanomaterials.

Light-Driven Catalytic Activity of Green-Synthesized SnO2/WO3-x Hetero-nanostructures

This work reports an environmentally friendly and economically feasible green synthesis of monometallic oxides (SnO₂ and WO₃) and their corresponding mixed metal oxide (SnO₂/WO_3-x) nanostructures from the aqueous Psidium guajava leaf extract for light-driven catalytic degradation of a major industrial contaminant, methylene blue (MB). P. guajava is a rich source of polyphenols that acts as a bio-reductant as well as a capping agent in the synthesis of nanostructures. The chemical composition and redox behavior of the green extract were investigated by liquid chromatography-mass spectrometry and cyclic voltammetry, respectively. Results acquired by X-ray diffraction and Fourier transform infrared spectroscopy confirm the successful formation of crystalline monometallic oxides (SnO₂ and WO₃) and bimetallic SnO₂/WO_3-x hetero-nanostructures capped with polyphenols. The structural and morphological aspects of the synthesized nanostructures were analyzed by transmission electron microscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. Photocatalytic activity of the synthesized monometallic and hetero-nanostructures was investigated for the degradation of MB dye under UV light irradiation. Results indicate a higher photocatalytic degradation efficiency for mixed metal oxide nanostructures (93.5%) as compared to pristine monometallic oxides SnO₂ (35.7%) and WO₃ (74.5%). The hetero-metal oxide nanostructures prove to be better photocatalysts with reusability up to 3 cycles without any loss in degradation efficiency or stability. The enhanced photocatalytic efficiency is attributed to a synergistic effect in the hetero-nanostructures, efficient charge transportation, extended light absorption, and increased adsorption of dye due to the enlarged specific surface area.

Biosynthesis of Gold and Silver Nanoparticles Using Phytochemical Compounds

Gold and silver nanoparticles are nanoparticles that have been widely used in various fields and have shown good benefits. The method of nanoparticle biosynthesis utilizing plant extracts, also known as green synthesis, has become a promising method considering the advantages it has compared to other synthesis methods. This review aims to give an overview of the phytochemical compounds in plants used in the synthesis of gold and silver nanoparticles, the nanoparticle properties produced using plant extracts based on the concentration and structure of phytochemical compounds, and their applications. Phytochemical compounds play an important role as reducing agents and stabilizers in the stages of the synthesis of nanoparticles. Polyphenol compounds, reducing sugars, and proteins are the main phytochemical compounds that are responsible for the synthesis of gold and silver nanoparticles. The concentration of phytochemical compounds affects the physical properties, stability, and activity of nanoparticles. This is important to know to be able to overcome limitations in controlling the physical properties of the nanoparticles produced. Based on structure, the phytochemical compounds that have ortho-substituted hydroxyl result in a smaller size and well-defined shape, which can lead to greater activity and stability. Furthermore, the optimal condition of the biosynthesis process is required to gain a successful reaction that includes setting the metal ion concentration, temperature, reaction time, and pH.

Optical properties of synthesized Au/Ag Nanoparticles using 532 nm and 1064 nm pulsed laser ablation: effect of solution concentration

The primary objective of this experimental research is to introduce the capacity of laser irradiation into the synthesis of bimetallic nanoparticles from noble metals. Gold and silver nanoparticles are produced through the laser ablating gold and silver targets in distilled water. Originally, the samples are synthesized by using Nd:YAG laser with 1064 nm wavelength and 7 ns pulse width. Following this, solutions mixed with different volumetric ratios, are irradiated by the second harmonic of the said laser at 532 nm wavelength. The absorption peak of gold nanoparticles around 530 nm, is used to transfer the laser energy to nanoparticles and synthesize Au/Ag bimetallic nanoparticles. The wavelength and volumetric ratio of solutions are the experiment's variables. The bimetallic nanoparticles are characterized as follows: X-ray diffraction pattern, spectroscopy in the range of UV–Vis-NIR and IR, Photoluminescence spectrum, Dynamic light scattering, and Fourier transform infrared spectroscopy. Additionally, FE-SEM and TEM images are used to study the size and morphology of nanoparticles. One of the aims of the research is to investigate the effects of laser wavelength and different volumetric concentrations on the optical properties of Au/Ag bimetallic nanoparticles. On the other hand, the study revealed that silver concentration and laser wavelength in the synthesis of Au/Ag bimetallic nanoparticles with different structures, cause the formation of crystalline structure, growth of grain size, and therefore silver oxide reduction.

Luminescent Gold Nanoclusters for Bioimaging: Increasing the Ligand Complexity

Fluorescence, and more in general, photoluminescence (PL), presents important advantages for imaging with respect to other diagnostic techniques. In particular, detection methodologies exploiting fluorescence imaging are fast and versatile; make use of low-cost and simple instrumentations; and are taking advantage of newly developed powerful, low-cost, light-based electronic devices, such as light sources and cameras, used in huge market applications, such as civil illumination, computers, and cellular phones. Besides the aforementioned simplicity, fluorescence imaging offers a spatial and temporal resolution that can hardly be achieved with alternative methods. However, the two main limitations of fluorescence imaging for bio-application are still (i) the biological tissue transparency and autofluorescence and (ii) the biocompatibility of the contrast agents. Luminescent gold nanoclusters (AuNCs), if properly designed, combine high biocompatibility with PL in the near-infrared region (NIR), where the biological tissues exhibit higher transparency and negligible autofluorescence. However, the stabilization of these AuNCs requires the use of specific ligands that also affect their PL properties. The nature of the ligand plays a fundamental role in the development and sequential application of PL AuNCs as probes for bioimaging. Considering the importance of this, in this review, the most relevant and recent papers on AuNCs-based bioimaging are presented and discussed highlighting the different functionalities achieved by increasing the complexity of the ligand structure.

Recent advances of Au@Ag core-shell SERS-based biosensors

The methodological advancements in surface-enhanced Raman scattering (SERS) technique with nanoscale materials based on noble metals, Au, Ag, and their bimetallic alloy Au-Ag, has enabled the highly efficient sensing of chemical and biological molecules at very low concentration values. By employing the innovative various type of Au, Ag nanoparticles and especially, high efficiency Au@Ag alloy nanomaterials as substrate in SERS based biosensors have revolutionized the detection of biological components including; proteins, antigens antibodies complex, circulating tumor cells, DNA, and RNA (miRNA), etc. This review is about SERS-based Au/Ag bimetallic biosensors and their Raman enhanced activity by focusing on different factors related to them. The emphasis of this research is to describe the recent developments in this field and conceptual advancements behind them. Furthermore, in this article we apex the understanding of impact by variation in basic features like effects of size, shape varying lengths, thickness of core-shell and their influence of large-scale magnitude and morphology. Moreover, the detailed information about recent biological applications based on these core-shell noble metals, importantly detection of receptor binding domain (RBD) protein of COVID-19 is provided.

Green Synthesized Silver Nanoparticle-Loaded Liposome-Based Nanoarchitectonics for Cancer Management: In Vitro Drug Release Analysis

Silver nanoparticles act as antitumor agents because of their antiproliferative and apoptosis-inducing properties. The present study aims to develop silver nanoparticle-loaded liposomes for the effective management of cancer. Silver nanoparticle-encapsulated liposomes were prepared using the thin-film hydration method coupled with sonication. The prepared liposomes were characterized by DLS (Dynamic Light Scattering analysis), FESEM (Field Emission Scanning Electron Microscope), and FTIR (Fourier Transform Infrared spectroscopy). The in vitro drug release profile of the silver nanoparticle-loaded liposomes was carried out using the dialysis bag method and the drug release profile was validated using various mathematical models. A high encapsulation efficiency of silver nanoparticle-loaded liposome was observed (82.25%). A particle size and polydispersity index of 172.1 nm and 0.381, respectively, and the zeta potential of -21.5 mV were recorded. FESEM analysis revealed spherical-shaped nanoparticles in the size range of 80-97 nm. The in vitro drug release profile of the silver nanoparticle-loaded liposomes was carried out using the dialysis bag method in three different pHs: pH 5.5, pH 6.8, and pH 7.4. A high silver nanoparticle release was observed in pH 5.5 which corresponds to the mature endosomes of tumor cells; 73.32 ± 0.68% nanoparticle was released at 72 h in pH 5.5. Among the various mathematical models analyzed, the Higuchi model was the best-fitted model as there is the highest value of the correlation coefficient which confirms that the drug release follows the diffusion-controlled process. From the Korsmeyer-Peppas model, it was confirmed that the drug release is based on anomalous non-Fickian diffusion. The results indicate that the silver nanoparticle-loaded liposomes can be used as an efficient drug delivery carrier to target cancer cells of various types.

Green Synthesis of Silver Nanoparticles Using Aerial Part Extract of the Anthemis pseudocotula Boiss. Plant and Their Biological Activity

Green syntheses of metallic nanoparticles using plant extracts as effective sources of reductants and stabilizers have attracted decent popularity due to their non-toxicity, environmental friendliness and rapid nature. The current study demonstrates the ecofriendly, facile and inexpensive synthesis of silver nanoparticles (AP-AgNPs) using the extract of aerial parts of the Anthemis pseudocotula Boiss. plant (AP). Herein, the aerial parts extract of AP performed a twin role of a reducing as well as a stabilizing agent. The green synthesized AP-AgNPs were characterized by several techniques such as XRD, UV-Vis, FT-IR, TEM, SEM and EDX. Furthermore, the antimicrobial and antibiofilm activity of as-prepared AP-AgNPs were examined by a standard two-fold microbroth dilution method and tissue culture plate methods, respectively, against several Gram-negative and Gram-positive bacterial strains and fungal species such as Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), multidrug-resistant Pseudomonas aeruginosa (MDR-PA) and Acinetobacter baumannii (MDR-AB), methicillin-resistant S. aureus (MRSA) and Candida albicans (C. albicans) strains. The antimicrobial activity results clearly indicated that the Gram-negative bacteria MDR-PA was most affected by AgNPs as compared to other Gram-negative and Gram-positive bacteria and fungi C. albicans. Whereas, in the case of antibiofilm activity, it has been found that AgNPs at 0.039 mg/mL, inhibit biofilms formation of Gram-negative bacteria i.e., MDR-PA, E. coli, and MDR-AB by 78.98 ± 1.12, 65.77 ± 1.05 and 66.94 ± 1.35%, respectively. On the other hand, at the same dose (i.e., 0.039 mg/mL), AP-AgNPs inhibits biofilm formation of Gram-positive bacteria i.e., MRSA, S. aureus and fungi C. albicans by 67.81 ± 0.99, 54.61 ± 1.11 and 56.22 ± 1.06%, respectively. The present work indicates the efficiency of green synthesized AP-AgNPs as good antimicrobial and antibiofilm agents against selected bacterial and fungal species.

Bentonite Nanoclay Optoelectrochemical Property Improvement through Bimetallic Silver and Gold Nanoparticles

This study assesses the physical and electrochemical changes of bimetallic Ag-Au nanoparticle-functionalized bentonite nanoclay. Nanoclay was studied to deduce a better sensing material/film. A chemical co-reduction method was used to synthesize bimetallic Ag-Au c nanoparticles, which were used to prepare a Ag-Au/PGV bentonite composite. Bimetallic Ag-AuNPs and their nanoclay composite were optically characterized using the scanning electron microscope, ultraviolet visible spectroscopy, X-ray diffraction, and Fourier transform infrared, whilst cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to ascertain their electrochemical activity and properties. The results of surface morphological inspection showed an average size of 10 nm, in agreement with XRD. The bimetallic Ag-AuNPs UV/Vis characteristic wavelengths of 414 nm and 516 nm confirmed the presence of Ag and Au metals, respectively. XRD exhibited diffraction planes related to 2θ values of Ag and Au metals, whilst FTIR indicated mainly COO- functional groups from the citrate capping of bimetallic Ag-Au NPs. CV and DPV showed that bentonite nanoclay is largely insulated by silicates but exhibited a small electroactivity of Fe. The electroactivity of Ag-Au/PGV bentonite exhibited peak potentials due to Ag/Ag+ and Au/Au3+ redox couples at 0.19 V/−0.20 V and 1.37 V/0.42, respectively. The Ag-Au/PGV bentonite nanocomposite exhibited the highest surface concentration of 3.25 × 10−2 cm2, a diffusion coefficient of 2.36 × −11 cm2/s, and an electron transfer rate constant (Ks) of 1.99 × 10−4 cm2. The outcome of these results indicated that the Ag-Au/PGV bentonite nanocomposite was more electroactive than PGV. Therefore, this study accentuates Ag-Au/PGV bentonite nanocomposite as a novel and promising platform for electrochemical sensing with higher sensitivity and efficiency than other sensing materials.

The identification of byproducts from the catalytic reduction reaction of 4-nitrophenol to 4-aminophenol: A systematic spectroscopic study

Acetaminophenol, commonly recognized as paracetamol (considered safer than aspirin) is formed by nitration of phenol (4-nitrophenol (4-NP)) for its conversion to 4-aminophenol (4-AP), followed by the acetylation for the final product. As 4-NP is an intermediate product in acetaminophenol (paracetamol) production from phenol the dynamic analysis of acetylation of amine group is important. This study focuses on the feasibility of spectroscopic studies to monitor the removal of 4-NP using sodium borohydride (NaBH₄) probe reaction in the presence of silver, gold, and bimetallic Ag/Au nanoparticles. UV-visible absorbance and fluorescence spectroscopy measurements reveal the formation of 1,4-benzoquinone (BQ), hydroquinone (HQ), and phenol (Ph) as the final products, in addition to the formation of typically reported 4-AP. The intermediates of NaBH₄ seem to play a significant role in the formation of BQ, which converts to HQ in the basic medium followed by the formation of phenol in an acidic medium. Complete kinetic analysis with respect to spectroscopic studies of the standard compounds is presented. Similar results were obtained with 4-NP spiked river and seawater samples. The present findings may lead to catalytic benchmarking that can differ from most of the current practices and highlight the importance of adopting a holistic approach towards the fundamental understanding of 4-NP catalytic reduction that must take into account the concentration of NaBH₄ and pH interdependencies.

Recent advances on botanical biosynthesis of nanoparticles for catalytic, water treatment and agricultural applications: A review

Green synthesis of nanoparticles using plant extracts minimizes the usage of toxic chemicals or energy. Here, we concentrate on the green synthesis of nanoparticles using natural compounds from plant extracts and their applications in catalysis, water treatment and agriculture. Polyphenols, flavonoid, rutin, quercetin, myricetin, kaempferol, coumarin, and gallic acid in the plant extracts engage in the reduction and stabilization of green nanoparticles. Ten types of nanoparticles involving Ag, Au, Cu, Pt, CuO, ZnO, MgO, TiO₂, Fe₃O₄, and ZrO₂ with emphasis on their formation mechanism are illuminated. We find that green nanoparticles serve as excellent, and recyclable catalysts for reduction of nitrophenols and synthesis of organic compounds with high yields of 83-100% and at least 5 recycles. Many emerging pollutants such as synthetic dyes, antibiotics, heavy metal and oils are effectively mitigated (90-100%) using green nanoparticles. In agriculture, green nanoparticles efficiently immobilize toxic compounds in soil. They are also sufficient nanopesticides to kill harmful larvae, and nanoinsecticides against dangerous vectors of pathogens. As potential nanofertilizers and nanoagrochemicals, green nanoparticles will open a revolution in green agriculture for sustainable development.

Silver Nanostructures prepared via novel green approach as an effective platform for biological and environmental applications

Silver nanoparticles play a significant role in biomedical sciences due to their unique properties allowing for their use as an effective sensing and remediation platform Herein, the green synthesis of silver nanostructures (Ag NSs), prepared via aqueous extract of waste Brassica oleracea leaves in the presence of silver nitrate solution (10^-4 M), is reported. The Ag NSs are fully characterized and their efficacy with respect to 4-nitrophenol reduction, glucose sensing, and microbes is determined. Visually, the color of silver nitrate containing solution altered from colorless to yellowish, then reddish grey, confirming the formation of Ag NSs. HRTEM and SEAD studies revealed the Ag NSs to have different morphologies (triangular, rod-shaped, hexagonal, etc., within a size range of 20–40 nm) with face-centered cubic (fcc) crystal structure. The Ag NSs possess high efficacy for nitrophenol reduction (<11 min and degradation efficiency of 98.2%), glucose sensing (LOD: 5.83 µM), and antimicrobial activity (E. coli and B. subtilis with clearance zones of 18.3 and 14 mm, respectively). Thus, the current study alludes towards the development of a cost-effective, sustainable, and efficient three-in-one platform for biomedical and environmental applications.

Recent Advances in Green Synthesis of Ag NPs for Extenuating Antimicrobial Resistance

Combating antimicrobial resistance (AMR) is an on-going global grand challenge, as recognized by several UN Sustainable Development Goals. Silver nanoparticles (Ag NPs) are well-known for their efficacy against antimicrobial resistance, and a plethora of green synthesis methodologies now exist in the literature. Herein, this review evaluates recent advances in biological approaches for Ag NPs, and their antimicrobial potential of Ag NPs with mechanisms of action are explored deeply. Moreover, short and long-term potential toxic effects of Ag NPs on animals, the environment, and human health are briefly discussed. Finally, we also provide a summary of the current state of the research and future challenges on a biologically mediated Ag-nanostructures-based effective platform for alleviating AMR.

Green Synthesis of Silver Nanoparticles Using Juniperus procera Extract: Their Characterization, and Biological Activity

Plant extract-based green synthesis of metal nanoparticles (NPs) has become a popular approach in the field of nanotechnology. In this present investigation, silver nanoparticles were prepared by an efficient and facile approach using Juniperus procera extract as a bioreducing and stabilizing agent. The as-synthesized silver nanoparticles (JP-AgNPs) were characterized by several characterization techniques such as UV–Vis, XRD, FT-IR, HR-TEM, and EDX analysis. The XRD analysis evidently confirms that the as-synthesized Ag nanoparticles (NPs) from Juniperus procera plant extract (JP-AgNPs) are crystalline in nature. FT-IR analysis confirms that the plant extract plays a dual role as a bioreducing and capping agent, while HR-TEM revealed the spherical morphology of as-synthesized JP-AgNPs with the size of ~23 nm. Furthermore, the synthesized JP-AgNPs were evaluated for antibacterial properties against several bacterial and fungal strains such as Staphylococcus aureus (ATCC 12228), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Proteus mirabilis (ATCC 4753), Cryptococcus neoformans (ATCC 16620), and Candida albicans (ATCC 885-653). The JP-AgNPs displayed an efficient mean zone of inhibition (MZI) at 50.00 µL for bacterial associated with fungal pathogens than the plant extract. Mainly, MZI values against microbial pathogens were as follows; E. coli (17.17 ± 0.72 mm), P. mirabilis (14.80 ± 0.17 mm), and C. albicans (14.30 ± 0.60 mm), whereas JP-AgNPs showed moderate activity against P. aeruginosa (11.50 ± 0.29 mm) and C. neoformans (9.83 ± 0.44 mm). Notably, the tested JP-AgNPs have displayed almost similar antimicrobial activities with that of standard antimicrobial drugs, such as streptomycin and nystatin. The enhanced antimicrobial activity of JP-AgNPs can be ascribed to the quality of resultant NPs including, uniform size, shape, and aqueous colloidal stability of nanoparticles.

Pulicaria undulata Extract-Mediated Eco-Friendly Preparation of TiO2 Nanoparticles for Photocatalytic Degradation of Methylene Blue and Methyl Orange

Eco-friendly approaches for the preparation of nanomaterials have recently attracted considerable attention of scientific community due to rising environmental distresses. The aim of the current study is to prepare titanium dioxide (TiO₂) nanoparticles (NPs) using an eco-friendly approach and investigate their performance for the photocatalytic degradation of hazardous organic dyes. For this, TiO₂ NPs were prepared by using the aqueous extract of the Pulicaria undulata (L.) plant in a single step at room temperature. Energy-dispersive X-ray spectroscopy established the presence of both titanium and oxygen in the sample. X-ray diffraction revealed the formation of crystalline, anatase-phase TiO₂ NPs. On the other hand, transmission election microscopy confirmed the formation of spherical shaped NPs. The presence of residual phytomolecules as capping/stabilization agents is confirmed by UV-vis analysis and Fourier-transform Infrared spectroscopy. Indeed, in the presence of P. undulata, the anatase phase of TiO₂ is stabilized at a significantly lower temperature (100 °C) without using any external stabilizing agent. The green synthesized TiO₂ NPs were used to investigate their potential for the photocatalytic degradation of hazardous organic dyes including methylene blue and methyl orange under UV-visible light irradiation. Due to the small size and high dispersion of NPs, almost complete degradation (∼95%) was achieved in a short period of time (between 1 and 2 h). No significant difference in the photocatalytic activity of the TiO₂ NPs was observed even after repeated use (three times) of the photocatalyst. Overall, the green synthesized TiO₂ NPs exhibited considerable potential for fast and eco-friendly removal of harmful organic dyes.

State of the Art on Green Route Synthesis of Gold/Silver Bimetallic Nanoparticles

Recently, bimetallic nanoparticles (BMNPs) blending the properties of two metals in one nanostructured system have generated enormous interest due to their potential applications in various fields including biosensing, imaging, nanomedicine, and catalysis. BMNPs have been developed later with respect to the monometallic nanoparticles (MNPs) and their physicochemical and biological properties have not yet been comprehensively explored. The manuscript aims at collecting the main design criteria used to synthetize BMNPs focusing on green route synthesis. The influence of experimental parameters such as temperature, time, reagent concentrations, capping agents on the particle growth and colloidal stability are examined. Finally, an overview of their nanotechnological applications and biological profile are presented.

Reduction of 4-nitrophenol using green-fabricated metal nanoparticles

Noble metal (silver (Ag), gold (Au), platinum (Pt), and palladium (Pd)) nanoparticles have gained increasing attention due to their importance in several research fields such as environmental and medical research. This review focuses on the basic perceptions of the green synthesis of metal nanoparticles and their supported-catalyst-based reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The mechanisms for the formation of these nanoparticles and the catalytic reduction of 4-NP are discussed. Furthermore, the parameters that need to be considered in the catalytic efficiency calculations and perspectives for future studies are also discussed.

Noble metal (silver (Ag), gold (Au), platinum (Pt), and palladium (Pd)) nanoparticles have gained increasing attention due to their importance in several research fields such as environmental and medical research.

Formation, antimicrobial activity, and biomedical performance of plant-based nanoparticles: a review

Because many engineered nanoparticles are toxic, there is a need for methods to fabricate safe nanoparticles such as plant-based nanoparticles. Indeed, plant extracts contain flavonoids, amino acids, proteins, polysaccharides, enzymes, polyphenols, steroids, and reducing sugars that facilitate the reduction, formation, and stabilization of nanoparticles. Moreover, synthesizing nanoparticles from plant extracts is fast, safe, and cost-effective because it does not consume much energy, and non-toxic derivatives are generated. These nanoparticles have diverse and unique properties of interest for applications in many fields. Here, we review the synthesis of metal/metal oxide nanoparticles with plant extracts. These nanoparticles display antibacterial, antifungal, anticancer, and antioxidant properties. Plant-based nanoparticles are also useful for medical diagnosis and drug delivery.

A Review on Plant-Mediated Synthesis of Bimetallic Nanoparticles, Characterisation and Their Biological Applications

The study of bimetallic nanoparticles (BNPs) has constantly been expanding, especially in the last decade. The biosynthesis of BNPs mediated by natural extracts is simple, low-cost, and safe for the environment. Plant extracts contain phenolic compounds that act as reducing agents (flavonoids, terpenoids, tannins, and alkaloids) and stabilising ligands moieties (carbonyl, carboxyl, and amine groups), useful in the green synthesis of nanoparticles (NPs), and are free of toxic by-products. Noble bimetallic NPs (containing silver, gold, platinum, and palladium) have potential for biomedical applications due to their safety, stability in the biological environment, and low toxicity. They substantially impact human health (applications in medicine and pharmacy) due to the proven biological effects (catalytic, antioxidant, antibacterial, antidiabetic, antitumor, hepatoprotective, and regenerative activity). To the best of our knowledge, there are no review papers in the literature on the synthesis and characterisation of plant-mediated BNPs and their pharmacological potential. Thus, an effort has been made to provide a clear perspective on the synthesis of BNPs and the antioxidant, antibacterial, anticancer, antidiabetic, and size/shape-dependent applications of BNPs. Furthermore, we discussed the factors that influence BNPs biosyntheses such as pH, temperature, time, metal ion concentration, and plant extract.

Biogenic synthesis of novel platinum-palladium bimetallic nanoparticles from aqueous Annona muricata leaf extract for catalytic activity

This work reports the fast and effective bio-fabrication of novel platinum-palladium bimetallic nanoparticles (Pt-Pd BNPs) along with their counterparts Pt and Pd monometallic NPs (MNPs) through aqueous Annona muricata leaf extract. The bio-fabrication of the NPs was achieved within 2 h at 100 °C and pH 7 which was established by the occurrence of dark brown color for Pt MNPs and black color for Pd MNPs and Pt-Pd BNPs. NPs were evaluated for their catalytic activity in the reduction of methyl orange (MO), rhodamine-B (rh-B), and methylene blue (MB) textile dyes in presence of sodium borohydride as a reducing agent. Pt-Pd (1:3) BNPs showed higher MO dye degradation (96.84 ± 2.05% in 50 min) followed by Pd MNPs (97.07 ± 1.46% in 60 min), Pt-Pd (3:1) BNPs (97.34 ± 1.17% in 70 min) and Pt-Pd (1:1) BNPs (98.12 ± 1.04% in 80 min). Pd MNPs showed significant catalytic activity in the reduction of rh-B dye by 97.27 ± 1.14% in 12 min followed by Pt-Pd (3:1) BNPs (96.76 ± 2.17% in 18 min), Pt-Pd (1:3) BNPs (96.53 ± 1.97% in 33 min) and Pt-Pd (1:1) BNPs (97.11 ± 2.09% in 39 min). Pt-Pd (1:3) BNPs also showed higher MB dye degradation (96.95 ± 1.57% in 40 min) followed by Pd MNPs (96.22 ± 2.36% in 55 min), Pt-Pd (3:1) BNPs (97.29 ± 1.22% in 75 min) and Pt-Pd (1:1) BNPs (96.45 ± 2.19% in 105 min). However, Pt MNPs showed no catalytic activity. Standard disc diffusion method was used to evaluate the NPs toxicity towards Escherichia coli and Staphylococcus aureus, which showed no inhibitory zones. NPs showed less toxicity compared to potassium dichromate (control) against Artemia nauplii. Among the NPs studied, Pt-Pd (1:1) BNPs showed less toxicity with 100% mortality only at 100 µg/mL concentration followed by Pt MNPs (≥ 80 µg/mL), Pt-Pd (1:3) BNPs (≥ 60 µg/mL), Pt-Pd (3:1) BNPs (≥ 60 µg/mL) and Pd MNPs (≥ 40 µg/mL) after 72 h exposure. These evaluations support the application of bio-fabricated Pt-Pd BNPs as nano-catalysts in textile dyes degradation.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02935-0.

Evaluation of the Anticancer Activity of Phytomolecules Conjugated Gold Nanoparticles Synthesized by Aqueous Extracts of Zingiber officinale (Ginger) and Nigella sativa L. Seeds (Black Cumin)

The conventional physical and chemical synthetic methods for the preparation of metal nanoparticles have disadvantages as they use expensive equipment and hazardous chemicals which limit their applications for biomedical purposes, and are not environment friendly. However, for the synthesis of biocompatible nanomaterials, plant-based techniques are eco-friendly and easy to handle. Herein a simple, single-step biosynthesis of gold nanoparticles using aqueous extracts of Nigella sativa (NSE) and Zingiber officinale (GE) as a reducing and capping agent has been demonstrated. The formation of gold nanoparticles (Au NPs) was confirmed by X-ray diffraction, UV-Vis, and EDS spectroscopies. Spectroscopic and chromatographic analysis of GE and NSE revealed the presence of bioactive phytochemical constituents, such as gingerol, thymoquinone, etc., which successfully conjugated the surface of resulting Au NPs. TEM analysis indicated the formation of smaller-sized, less-aggregated, spherical-shaped Au NPs both in the case of GE (~9 nm) and NSE (~11 nm). To study the effect of the concentration of the extracts on the quality of resulting NPs and their anticancer properties, three different samples of Au NPs were prepared from each extract by varying the concentration of extracts while keeping the amount of precursor constant. In both cases, high-quality, spherical-shaped NPs were obtained, only at a high concentration of the extract, whereas at lower concentrations, larger-sized, irregular-shaped NPs were formed. Furthermore, the as-prepared Au NPs were evaluated for the anticancer properties against two different cell lines including MDA-MB-231 (breast cancer) and HCT 116 (colorectal cancer) cell lines. GE-conjugated Au NPs obtained by using a high concentration of the extract demonstrated superior anticancer properties when compared to NSE-conjugated counterparts.

Controllable Synthesis of Bimetallic Nanostructures Using Biogenic Reagents: A Green Perspective

Bimetallic nanostructures are emerging as a significant class of metal nanomaterials due to their exceptional properties that are useful in various areas of science and technology. When used for catalysis and sensing applications, bimetallic nanostructures have been noted to exhibit better performance relative to their monometallic counterparts owing to synergistic effects. Furthermore, their dual metal composition and configuration can be modulated to achieve optimal activity for the desired functions. However, as with other nanostructured metals, bimetallic nanostructures are usually prepared through wet chemical routes that involve the use of harsh reducing agents and hazardous stabilizing agents. In response to intensifying concerns over the toxicity of chemicals used in nanomaterial synthesis, the scientific community has increasingly turned its attention toward environmentally and biologically compatible reagents that can enable green and sustainable nanofabrication processes. This article aims to provide an evaluation of the green synthetic methods of constructing bimetallic nanostructures, with emphasis on the use of biogenic resources (e.g., plant extracts, DNA, proteins) as safe and practical reagents. Special attention is devoted to biogenic synthetic protocols that demonstrate controllable nanoscale features, such as size, composition, morphology, and configuration. The potential use of these biogenically prepared bimetallic nanostructures as catalysts and sensors is also discussed. It is hoped that this article will serve as a valuable reference on bimetallic nanostructures and will help fuel new ideas for the development of more eco-friendly strategies for the controllable synthesis of various types of nanostructured bimetallic systems.

Biogenic synthesis of bimetallic nanoparticles and their applications

The current advancements in nanotechnology suggest a sustainable development in the green synthesis of bimetallic nanoparticles (BMNPs) through green approaches. Though challenging, nano phyto technology has versatile methods to achieve desired unique properties like optic, electronic, magnetic, therapeutic, and catalytic efficiencies. Bio-inspired, facile synthesis of bifunctional BMNPs is possible using abundant, readily available natural plant sources, bio-mass wastes and microorganisms. Synergistic effects of two different metals on mixing, bring new insight for the vast applications, which is not achievable in using monometallic NPs. By adopting bio-inspired greener approaches for synthesizing NPs, the risk of environmental toxicity caused by conventional physicochemical methods become negligible. This article hopes to provide the significance of cost-effective, one-step, eco-friendly and facile synthesis of noble/transition bimetallic NPs. This review article endows an overview of the bio-mediated synthesis of bimetallic NPs, classifications of BMNPs, current characterization techniques, possible mechanistic aspects for reducing metal ions, and the stability of formed NPs and bio-medical/industrial applications of fabricated NPs. The review also highlights the prospective future direction to improve reliability, reproducibility of biosynthesis methods, its actual mechanism in research works and extensive application of biogenic bimetallic NPs.

Green Silver and Gold Nanoparticles: Biological Synthesis Approaches and Potentials for Biomedical Applications

The nanomaterial industry generates gigantic quantities of metal-based nanomaterials for various technological and biomedical applications; however, concomitantly, it places a massive burden on the environment by utilizing toxic chemicals for the production process and leaving hazardous waste materials behind. Moreover, the employed, often unpleasant chemicals can affect the biocompatibility of the generated particles and severely restrict their application possibilities. On these grounds, green synthetic approaches have emerged, offering eco-friendly, sustainable, nature-derived alternative production methods, thus attenuating the ecological footprint of the nanomaterial industry. In the last decade, a plethora of biological materials has been tested to probe their suitability for nanomaterial synthesis. Although most of these approaches were successful, a large body of evidence indicates that the green material or entity used for the production would substantially define the physical and chemical properties and as a consequence, the biological activities of the obtained nanomaterials. The present review provides a comprehensive collection of the most recent green methodologies, surveys the major nanoparticle characterization techniques and screens the effects triggered by the obtained nanomaterials in various living systems to give an impression on the biomedical potential of green synthesized silver and gold nanoparticles.

Ecofriendly Synthesis of Silver Nanoparticles Using Aqueous Extracts of Zingiber officinale (Ginger) and Nigella sativa L. Seeds (Black Cumin) and Comparison of Their Antibacterial Potential

Applications of chemical synthetic methods for the preparation of metal nanoparticles involve toxic reagents, which are hazardous to both humans and the environment. On the other hand, ecofriendly plant-based techniques offer rapid, non-toxic, and suitable alternatives to the traditional methods. Herein, we report an eco-friendly method for the preparation of silver nanoparticles (Ag NPs) using two different aqueous extracts of Zingiber officinale (ginger) and Nigella sativa L. seeds (black cumin). Successful preparation of Ag NPs was confirmed by X-ray diffraction, ultraviolet–visible (UV-Vis) spectroscopy, and energy dispersive spectroscopy (EDX). Transmission electron microscopy (TEM) analysis revealed that Nigella sativa L. seed extract (NSE) produced a smaller size of NPs (~8 nm), whereas the ginger extract (GE) led to the formation of slightly larger Ag NPs (~12 nm). In addition, to study the effect of concentration of the extract on the quality of resulting NPs, two different samples were prepared from each extract by increasing the concentrations of the extracts while using a fixed amount of precursor (AgNO3). In both cases, a high concentration of extract delivered less agglomerated and smaller-sized Ag NPs. Furthermore, the antibacterial properties of as-prepared Ag NPs were tested against different bacterial strains. Notably, despite the slightly better quality of Ag NPs obtained from NSE (NSE-Ag), NPs prepared by using GE (GE-Ag) demonstrated superior antibacterial properties. In case of the plant-extract-based synthesis of nanoparticles, it is widely reported that during the preparation, the residual phytomolecules remain on the surface of resulting NPs as stabilizing agents. Therefore, in this case, the high antibacterial properties of GE-Ag can be attributed to the contributing or synergetic effect of residual phytomolecules of GE extract on the surface of Ag NPs, since the aqueous extract of GE has been known to possess higher intrinsic bactericidal properties when compared to the aqueous NSE extract.