Green silver-nanoparticle-based dual sensor for toxic Hg(II) ions

A dual-modality sensing probe of fluorescent and colorimetric for detection of cobalt ion based on silver nanoparticles functionalized rhodamine 6G derivatives

The combination of fluorescent probe and colorimetric technique has become one of the most powerful analytical methods due to the advantages of visualization, minimal measurement errors and high sensitivity. Hence, a novel dual-modality sensing probe with both colorimetric and fluorescent capabilities was developed for detecting cobalt ions (Co2+) based on homocysteine mediated silver nanoparticles and rhodamine 6G derivatives probe (AgNPs-Hcy-Rh6G2). The fluorescence of the AgNPs-Hcy-Rh6G2 probe turned on due to the opening of the Rh6G2 spirolactam ring in the presence of Co2+ by a catalytic hydrolysis. The fluorescent intensity of probe is proportional to Co2+ concentration in the range of 0.10-50 μM with a detection limit of 0.05 μM (S/N = 3). More fascinatingly, the color of AgNPs-Hcy-Rh6G2 probe changed from colorless to pink with increasing Co2+ concentration, which allowing colorimetric determination of Co2+. The absorbance of AgNPs-Hcy-Rh6G2 probe is proportional to Co2+ concentration in the range from 0.10 to 25 μM with a detection limit of 0.04 μM (S/N = 3). This colorimetric and fluorescent dual-modal method exhibited good selectivity, and reproducibility and stability, holding great potential for real samples analysis in environmental and drug field.

Low-Cost Plant-Based Metal and Metal Oxide Nanoparticle Synthesis and Their Use in Optical and Electrochemical (Bio)Sensors

Technological progress has led to the development of analytical tools that promise a huge socio-economic impact on our daily lives and an improved quality of life for all. The use of plant extract synthesized nanoparticles in the development and fabrication of optical or electrochemical (bio)sensors presents major advantages. Besides their low-cost fabrication and scalability, these nanoparticles may have a dual role, serving as a transducer component and as a recognition element, the latter requiring their functionalization with specific components. Different approaches, such as surface modification techniques to facilitate precise biomolecule attachment, thereby augmenting recognition capabilities, or fine tuning functional groups on nanoparticle surfaces are preferred for ensuring stable biomolecule conjugation while preserving bioactivity. Size optimization, maximizing surface area, and tailored nanoparticle shapes increase the potential for robust interactions and enhance the transduction. This article specifically aims to illustrate the adaptability and effectiveness of these biosensing platforms in identifying precise biological targets along with their far-reaching implications across various domains, spanning healthcare diagnostics, environmental monitoring, and diverse bioanalytical fields. By exploring these applications, the article highlights the significance of prioritizing the use of natural resources for nanoparticle synthesis. This emphasis aligns with the worldwide goal of envisioning sustainable and customized biosensing solutions, emphasizing heightened sensitivity and selectivity.

A highly selective Hg2+ colorimetric sensor and antimicrobial agent based on green synthesized silver nanoparticles using Equisetum diffusum extract

Plasmonic nanoparticles such as Ag have gained great interest in the biomedical domain and chemical analysis due to their unique optical properties. Herein, we report a simple, cost-effective, and highly selective colorimetric sensor of mercury(ii) based on E. diffusum (horsetail) extract-functionalized Ag nanoparticles (ED-AgNPs). The ED-AgNPs were synthesized by exploiting the coordination of Ag+ with the various functional groups of ED extract under sunlight exposure for only tens of seconds. ED-AgNPs (63 nm) were characterized using various techniques such as UV-vis, FTIR, DLS, SEM and EDX. FTIR spectra suggested the successful encapsulation of the AgNPs surface with ED extract and XRD confirmed its crystalline nature. This ED-AgNPs colorimetric sensor revealed remarkable selectivity towards Hg2+ in aqueous solution among other transition metal ions through a redox reaction mechanism. Besides, the sensor exhibited high sensitivity with rapid response and a detection limit of 70 nM. The sensor demonstrated feasibility for Hg(ii) detection in spiked tap and river water samples. In addition, the synthesized ED-AgNPs revealed enhanced antimicrobial activity with higher efficacy against the Gram-positive bacterium (L. monocytogenes with an inhibition zone of 18 mm) than the Gram-negative bacterium (E. coli with an inhibition zone of 10 mm). The simplicity and adaptability of this colorimetric sensor render it a promising candidate for on-site and point-of-care detection of heavy metal ions in diverse conditions.

The Role of Silver Nanoparticles in Electrochemical Sensors for Aquatic Environmental Analysis

With rapidly increasing environmental pollution, there is an urgent need for the development of fast, low-cost, and effective sensing devices for the detection of various organic and inorganic substances. Silver nanoparticles (AgNPs) are well known for their superior optoelectronic and physicochemical properties, and have, therefore, attracted a great deal of interest in the sensor arena. The introduction of AgNPs onto the surface of two-dimensional (2D) structures, incorporation into conductive polymers, or within three-dimensional (3D) nanohybrid architectures is a common strategy to fabricate novel platforms with improved chemical and physical properties for analyte sensing. In the first section of this review, the main wet chemical reduction approaches for the successful synthesis of functional AgNPs for electrochemical sensing applications are discussed. Then, a brief section on the sensing principles of voltammetric and amperometric sensors is given. The current utilization of silver nanoparticles and silver-based composite nanomaterials for the fabrication of voltammetric and amperometric sensors as novel platforms for the detection of environmental pollutants in water matrices is summarized. Finally, the current challenges and future directions for the nanosilver-based electrochemical sensing of environmental pollutants are outlined.

Green synthesis of Piper chaudocanum stem extract mediated silver nanoparticles for colorimetric detection of Hg2+ ions and antibacterial activity

A green synthetic approach to synthesize silver nanoparticles (AgNPs) using the stem extract of Piper chaudocanum for highly sensitive colorimetric detection of Hg²⁺ with a low limit of detection of 23 nM and easy colorimetric read-out has been reported. In addition, the biosynthesized AgNPs demonstrated efficient antibacterial activity against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. The morphology and structure of the as-synthesized AgNPs were examined using SEM, TEM, EDX, XRD and FT-IR analyses. The XRD and TEM results confirm the formation of AgNPs with an average particle size of 8-12 nm. The TLC, CC and HPLC revealed that four main compounds, pentacosanoic acid (1), piperine (2), β-sitosterol (3), and campesterol glucoside (4), isolated from P. chaudocanum extract act as reducing and stabilizing agents for AgNP formation, and piperine plays a vital role in green synthesis. The chemical structures of these compounds were determined by ESI MS, FTIR, and one- and two-dimensional NMR spectroscopic data analysis. This approach is an efficient, green, cost-effective, eco-friendly and promising technique for synthesizing AgNPs with applications in the colorimetric detection of Hg²⁺ and antibacterial activity.

Green synthesis of silver nanoparticles using Coffea canephora fruit skin extract and its application for mercury detection in face cream samples

Mercury is one of the most toxic heavy metals causing harmful effects on the human body; meanwhile, mercury is found in some face cream products to give a whitening effect. The upper limit concentration of mercury in skin-lightening products defined by the Food and Drug Administration (FDA) is under one mg/L as Hg²⁺. A new green analytical spectrophotometric method for mercury analysis has been developed by employing a biological reagent from fruit skin extract of robusta coffee (Coffea canephora) as a bioreductor for silver ions as well as a stabilizer for the AgNPs product. The detection principle of this method is based on the decrease of the color intensity of silver nanoparticles (AgNPs) after the addition of Hg²⁺ ions due to the re-oxidization of the AgNPs by Hg²⁺ ions to colorless Ag⁺ ions. To achieve the most significant sensitivity, linearity of measurement, and validity, the method was optimized toward the volume of AgNPs and reaction time. In this research, the synthesized AgNPs were also characterized by UV-Vis Spectrometry as well as a particle size analyzer (PSA) to determine the size of nanoparticles. The result showed that the optimum conditions were attained at 4 mL AgNPs solution and 3-min reaction resulting in a linear measurement of Hg²⁺ in the range of 0-15 mg/L with LOD and LOQ of 0.039 and 0.130 mg/L, respectively. This method is quite selective and has been validated by applying it to real face cream samples with satisfactory results supported by average recoveries of close to 100%.

Statistical optimization of silver nanoparticle synthesis by green tea extract and its efficacy on colorimetric detection of mercury from industrial waste water

For the optimization of silver nanoparticle production, a central composite design was used with three parameters: AgNO₃ concentration, green tea extract concentration, and temperature at three different levels. The size of the synthesized silver nanoparticle, its UV absorbance, zeta potential, and polydispersity index were set as the response parameters. Silver nanoparticles obtained in the optimization process were characterized and its efficacy on colorimetric detection of mercury was evaluated. The response variables were significant for the factors analyzed, and each variable had a significant model (P < 0.05). The ideal conditions were: 1 mM AgNO₃, 0.5% green tea extract, and 80 °C temperature. To analyze the produced AgNPs under certain ideal conditions, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used. The UV-visible spectra of AgNPs revealed an absorption maxima at 424 nm. The XRD pattern reveals a significant diffraction peak at 38.25°, 44.26°, 64.43°, and 77.49°, which corresponds to the (111), (200), (220), and (311) planes of polycrystalline face-centered cubic (fcc) silver, respectively. The TEM and SEM analyses confirmed that the particles were spherical, and dynamic light scattering study determined the average diameter of AgNPs to be 77.4 nm. The AgNPs have a zeta potential of -62.6 mV, as determined by the zeta sizer analysis. The AgNPs detects mercury at a micromolar concentration. Furthermore, the environmentally friendly generated AgNPs were used to detect mercury in a colorimetric method that was effectively employed for analytical detection of Hg²⁺ ions in an aqueous environment for the purpose of practical application.

Biosustainable production of nanoparticles via mycogenesis for biotechnological applications: A critical review

The demand for the green synthesis of nanoparticles has gained prominence over the conventional chemical and physical syntheses, which often entails toxic chemicals, energy consumption and ultimately lead to negative environmental impact. In the green synthesis approach, naturally available bio-compounds found in plants and fungi can be effective and have been proven to be alternative reducing agents. Fungi or mushrooms are particularly interesting due to their high content of bioactive compounds, which can serve as excellent reducing agents in the synthesis of nanoparticles. Apart from the economic and environmental benefits, such as ease of availability, low synthesis/production cost, safe and no toxicity, the nanoparticles synthesized from this green method have unique physical and chemical properties. Stabilisation of the nanoparticles in an aqueous solution is exceedingly high, even after prolonged storage with unperturbed size uniformity. Biological properties were significantly improved with higher biocompatibility, anti-microbial, anti-oxidant and anti-cancer properties. These remarkable properties allow further exploration in their applications both in the medical and agricultural fields. This review aims to explore the mushroom-mediated biosynthesis of nanomaterials, specifically the mechanism and bio-compounds involved in the synthesis and their interactions for the stabilisation of nanoparticles. Various metal and non-metal nanoparticles have been discussed along with their synthesis techniques and parameters, making them ideal for specific industrial, agricultural, and medical applications. Only recent developments have been explored in this review.

GC-MS based lemon grass metabolite analysis involved in the synthesis of silver nanoparticles and evaluation of photo-catalytic degradation of methylene blue

Silver nanoparticles (AgNPs) is of great importance to scientific community due to their plethora of applications. Several plant extracts have been reported for synthesis of AgNPs. In this study, lemon grass was used as a reducing and capping agent to prepare AgNPs. The formation of AgNPs was confirmed by using UV-Vis spectra as AgNPs show a characteristic peak around 400 nm. Effect of pH, temperature and lemon grass extract to silver nitrate ratio was optimized using response surface methodology (RSM). Characterization of AgNPs was done using X-Ray Diffraction (XRD), Energy Dispersive X-Ray spectroscopy (EDX), Trasmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). Gas Chromatography-Mass spectrometry (GC-MS), Energy Dispersive X-Ray spectroscopy and Fourier Transform-Infrared (FT-IR) spectroscopic analysis showed involvement of metabolites of lemon grass in the formation of AgNPs. Photo-catalytic activity of synthesized AgNPs was evaluated through degradation of organic pollutant methylene blue dye.

Recent Trends in Noble Metal Nanoparticles for Colorimetric Chemical Sensing and Micro-Electronic Packaging Applications

Noble metal NPs are highly attractive candidates because of their unique combination of physical, chemical, mechanical, and structural properties. A lot of developments in this area are still fascinating the materials research community, and are broadly categorized in various sectors such as chemical sensors, biosensors, Förster resonance energy transfer (FRET), and microelectronic applications. The related function and properties of the noble metals in these areas can be further tailored by tuning their chemical, optical, and electronic properties that are influenced by their size, shape, and distribution. The most widely used Au and Ag NPs in dispersed phase below 100 nm exhibit strong color change in the visible range which alters upon aggregation of the NPs. The chemical sensing of the analyte is influenced by these NPs aggregates. In this article, we have summarized the uniqueness of noble metal NPs, their synthesis methods, nucleation and growth process, and their important applications in chemical sensing, microelectronic packaging, and Förster resonance energy transfer.

Highly selective and sensitive tool for the detection of Hg(II) using 3-(Trimethoxysilyl) propyl methacrylate functionalized Ag-Ce nanocomposite from real water sample

Mercury and its derivates cause distinct toxicity and it is detrimental to the ecosystem where the excessive concentration contributes towards the environmental pollutants. The current study reported a colorimetric method for the detection of Hg(II) ion with high specificity and selectivity using Ag-Ce nanocomposite (NC) functionalized by 3-(Trimethoxysilyl) propyl methacrylate. The synthesized Ag-Ce NC was characterized by using double beam UV-visible spectrophotometer, zeta sizer, EDS, TEM, FT-IR, XRD and particle size analyzer. The synthesized particle possessed an average particle size of 27 ± 1 nm and zeta potential of -39.32 ± 3 mV. The brownish yellow colored Ag-Ce NC changed to colorless in presence of Hg(II) where the colorimetric detection was extremely specific and superior towards Hg(II) ion on comparing the tests with other metal ions. An excellent linear correlation was observed between absorbance (395 nm) and Hg(II) concentrations (1 nM-10 μM) (R² = 0.988) with LOD of 0.03 nM. A cotton swab based probe was prepared for selective, elegant and low cost colorimetric method to detect Hg(II). The parametric study was performed for optimizing the suitable condition. The colorimetric probe developed by this study for Hg(II) detection using Ag-Ce NC shows excellent practical applicability.

Preparation of Ag-cellulose nanocomposite for the selective detection and quantification of mercury at nanomolar level and the evaluation of its photocatalytic performance

Mercury is a toxic heavy metal that reaches to the water bodies mainly by coal burning, mining and petrol refining. The study was focused to investigate the application of Ag-cellulose nanocomposite to detect and quantify mercury colorimetrically. The Ag-cellulose nanocomposite was characterized by X-ray diffraction, Transmission electron microscopy, Fourier transform infrared spectroscopy, UV-visible spectroscopy, particle size analyzer and zetasizer. The study identified that the presence of other metal ions did not interfere with the detection of Hg²⁺ ion by the probe. The prepared Ag-cellulose nanocomposite-phenylalanine conjugate incorporated paper strip showed an excellent result in Hg²⁺ detection. The Ag-cellulose nanocomposite was used to quantify the unknown concentration of mercury on real sample (environmental sample) and it was found to be highly accurate by confirming with atomic absorption spectrophotometric analysis. The Ag-cellulose nanocomposite showed effective detection at 45 °C, pH 9 and 0.1% of salinity. The Ag-cellulose nanocomposite showed efficient photocatalytic performance under visible light irradiation. The half-life period of MB by Ag-cellulose nanocomposite under visible light was determined to be 90 min. The study suggests the application of prepared probe in photocatalysis and the detection of Hg²⁺ from various environmental samples.

Metal Nanoparticles Formation from Nickel Hydroxide

In this study, the mechanism of nickel nanoparticle formation from its hydroxide was analyzed. Metallic nickel nanoparticles were obtained through the hydroxide’s reduction under hydrogen. Nickel hydroxides were produced from nickel (II) nitrate hexahydrate and NaOH by deposition under various initial conditions. The influence of washing treatment on the dispersion of obtained nickel powders was studied. The washing procedure of precipitates was carried out by centrifugation, ultrasonic treatment, and decantation. X-ray diffractometry, transmission electron microscopy, low-temperature nitrogen adsorption, infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy methods were used for nanoparticle characterization. Based on the resulting data, a model of the Ni(OH)₂ aggregate structure after deposition was proposed. The number of nickel hydroxide particles required to form one nickel nanoparticle was estimated, and a model of its formation was proposed.

Facile colorimetric detection of Hg (II), photocatalytic and antibacterial efficiency based on silver-manganese disulfide/polyvinyl alcohol-chitosan nanocomposites

The application of nano materials for removal and detection of hazardous metal detection with nanoparticles is important for researcher. In this paper, the silver-manganese disulfide/chitosan-polyvinyl alcohol (Ag-MnS₂/CSPVA) nanocomposites was prepared for the detection of toxic heavy metal. The synthesized nano materials was experimented through the various analysis methods to structural and morphological evaluation. The surface charge of the Ag-MnS₂/CSPVA was -25.0 ± 0.1 mV. The various metal ions have not effect on detection of mercury (II). The result shows the excellent linearity was found the mercury concentrations changing with limit of detection of 9.0 nM (nano molar level). The condition of detection was conducted at pH 5 and room temperature. Moreover, the photocatalytic properties of the Ag-MnS₂/CSPVA nanocomposites was analyzed for degradation of malachite green under visible light irradiation. The complete malachite green degradation reached up to 97.29% after 30 min of photocatalytic reaction. The antibacterial efficiency was studied versus both Escherichia coli and Staphylococcus aureus bacteria. The outcome depicts that the Ag-MnS₂/CSPVA nanocomposites has an excellent property in antibacterial activity.

Rapid colorimetric detection of mercury using silver nanoparticles in the presence of methionine

Development of potential sensors is inevitable for the detection of environmental pollutants including toxins, organic pollutants and heavy metal which cause hazardous effect to human and other living organisms. The present study is to develop silver nanoparticle (Ag NPs) based sensor for the accurate, sensitive and selective colorimetric detection of Hg²⁺ ions from aqueous samples at nano molar level. The nanoparticles were synthesized chemically and it was stabilized by polyvinylpyrrolidone (PVP). The prepared particles were characterized by UV-visible spectroscopy, scanning electron microscopy (SEM), particle analysiser and Zetasizer. The UV-visible spectra of Ag NPs showed absorbance maximum at 392 nm. The average diameter of Ag NPs was determined to be 6 ± 0.9 nm by using particle analyzer. The zeta sizer analysis showed that the PVP stabilized Ag NPs possessed a zeta potential of -35.56 ± 3 mV. The Ag NPs-methionine conjugate showed the colour change from the brownish yellow colour to colourless when it was reacted with mercury. The Ag NPs conjugated methionine is sensitive to mercury and detects the mercury at nano molar level. The influence of other metal ion did not interfere with the detection and quantification of Hg²⁺. The detection of Hg²⁺ was also performed with paper strip and agarose gel method. The Ag NPs conjugate with methionine can applied for the detection of Hg²⁺ from various aqueous samples.

Gold, Silver and Iron Oxide Nanoparticles: Synthesis and Bionanoconjugation Strategies Aimed at Electrochemical Applications

Nanomaterials have revolutionized the sensing and biosensing fields, with the development of more sensitive and selective devices for multiple applications. Gold, silver and iron oxide nanoparticles have played a particularly major role in this development. In this review, we provide a general overview of the synthesis and characteristics of gold, silver and iron oxide nanoparticles, along with the main strategies for their surface functionalization with ligands and biomolecules. Finally, different architectures suitable for electrochemical applications are reviewed, as well as their main fabrication procedures. We conclude with some considerations from the authors' perspective regarding the promising use of these materials and the challenges to be faced in the near future.

A Sensitive Isoniazid Capped Silver Nanoparticles - Selective Colorimetric Fluorescent Sensor for Hg2+ Ions in Aqueous Medium

Novel isonicotinic acid hydrazide functionalized silver nanoparticles (INH-AgNPs) were synthesized by wet chemical method and used for the detection of Hg²⁺ ions in aqueous medium. The INH-AgNPs exhibit good absorbance and emission peaks by sensing Hg²⁺ ions with visible color changes. The detection of Hg²⁺ ions was confirmed by FT-IR, EDAX spectra and by the changing morphology of INH-AgNPs, and after addition of Hg²⁺ was confirmed by SEM and TEM imaging studies. Based on the emission intensity the probe INH-AgNPs exhibit a lowest detection limit (LOD) of Hg²⁺ to 0.18 nM. The association constant (K_a) of INH-AgNPs + Hg²⁺ ions is calculated using the Bensei-Hildebrand equation. Also, the probe is successfully utilized for the detection of Hg²⁺ ions in real water samples obtained from different fields, which showed good results.

Gum acacia-based silver nanoparticles as a highly selective and sensitive dual nanosensor for Hg(ii) and fluorescence turn-off sensor for S2− and malachite green detection

A facile and green method was adopted to synthesize highly selective gum acacia-mediated silver nanoparticles as dual sensor (fluorescence turn-on and colorimetric) for Hg(ii) and fluorescence turn-off sensor for S²⁻ and malachite green. The mechanism proposed for a dual response towards Hg(ii) is the redox reaction between Ag(0) and Hg(ii), resulting in the formation of Ag(i) and Hg(0) and electron transfer from gum acacia to Ag(i), which further leads to the formation of an Ag@Hg nanoalloy. The enhanced fluorescence signal was quenched selectively by S²⁻ owing to the formation of Ag₂S and HgS. The reported nanosensor was found to be useful for sensing malachite green via the inner filter effect. The linear ranges were 3 nmol L⁻¹ to 13 μmol L⁻¹ for Hg(ii), 3–170 μmol L⁻¹ for S²⁻ and 7–80 μmol L⁻¹ for malachite green, and the corresponding detection limits were 2.1 nmol L⁻¹ for Hg(ii), 1.3 μmol L⁻¹ for S²⁻ and 1.6 μmol L⁻¹ for malachite green.

Gum acacia-stabilized silver nanoparticles for the detection of Hg(ii), S²⁻ and malachite green.

Tweaking the proton transfer triggered proton transfer of 3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazole

Proton transfer triggered proton transfer (PTTPT) of the molecule is completely altered by dimethylformamide and the proton transfer paths are changed. The process can be reversed by silver particle.