Characteristic Surface Plasmon Resonance Band Research Articles

Characterization of Copper Nanoparticles synthesized Using the Leaf Extracts of Lawsonia inermis, Eucalyptus globulus, Psidium guajava, and Azadirachta indica

Green synthesis of nanoparticles using plant extracts is a sustainable, eco-friendly, non-toxic, and cost-efficient approach. In this study, copper nanoparticles (CuNPs) were synthesized using the mehandi Lawsonia inermis, nilgiri Eucalyptus globulus, guava Psidium guajava, or neem Azadirachta indica leaf extracts and 1mM CuSO4.5H2O salt solution in a ratio of 1:3 at 800C temperature and characterized using UV-Visible spectroscopy, Fourier Transform Infrared spectroscopy, and Field Emission Scanning Electron Microscopy analysis. All the CuNPs showed colour change with characteristic surface plasmon resonance bands. The plasmon resonance bands of L. inermis, P. guajava, and A. indica CuNPs peaked at 300nm while those of E. globulus CuNPs peaked at 400nm. The CuNPs synthesized from L. inermis, E. globulus, and P. guajava leaf extracts exhibited brown colour while those synthesized from A. indica leaf extracts showed green colour. Eleven bands were present in L. inermis and A. indica CuNPs in the range of 538.61-3649.06cm-1 and 3867.26-519.02cm-1, respectively, while ten were in the E. globulus and P. guajava CuNPs in the range of 407.25-3326.78cm-1 and 3325.93-407.07cm-1, respectively. The L. inermis, E. globulus, and A. indica CuNPs were spherical, except P. guajava CuNPs which were flaky in shape. The particle size of L. inermis CuNPs was found in the range of 8.20 to 15.94nm; E. globulus CuNPs in the range of 7.52 to 67.47nm; P. guajava CuNPs in the range of 18.90 to 73.80nm and A. indica CuNPs in the range of 9.86 to 22.05nm.

Characterization of Zinc Nanoparticles Synthesized Using the Mushroom, Pleurotus sajor-caju

Fungi including mushrooms contain various enzymes and biomolecules, making them an effective agent for synthesizing various nanoparticles. This study aimed to synthesize and characterize zinc nanoparticles using the zinc sulphate salt at the concentration of 1mM and the mushroom Pleurotus sajor-caju. The P. sajor-caju synthesized zinc nanoparticles were characterized using UV-Visible spectral analysis, Field Emission Scanning Electron Microscopy, and Fourier Transform Infrared Spectroscopy. They did not change the color and showed a characteristic surface plasmon resonance band peaking at 300nm. They were spherical and the particle size was found in the range of 7.29 nm to 13.27 nm. They showed ten bands at different stretching with wave numbers ranging between 675.17cm-1 and 3675.56cm-1. The presence of advantageous features in the zinc nanoparticles synthesized from P. sajor-caju revealed the usefulness of the synthesis of other metal nanoparticles from P. sajor-caju.

Anticancer potential of silver nanoparticles biosynthesized using Catharanthus roseus leaves extract on cervical (HeLa229) cancer cell line

Cervical cancer is a significant global health issue among women due to its prevalence and impact on morbidity and mortality, especially in low- and middle-income countries. This underscores the critical necessity for the development of anticancer treatments that are not only more efficient but also safer. This study introduces a novel approach to combating cervical cancer by synthesizing silver nanoparticles (AgNPs) using aqueous Catharanthus roseus leaves extract and evaluating their anticancer activity. The aqueous extract of C. roseus showed remarkable potential to reduce silver ions rapidly. UV–Vis spectroscopy confirmed the formation of AgNPs, with a characteristic surface plasmon resonance (SPR) band observed at 429 nm. TEM/EDX and FE-SEM analysis confirmed the presence of spherical AgNPs with uniform size distribution. XRD analysis confirmed the face-centered cubic (FCC) structure of metallic silver in AgNPs. Moreover, AgNPs exhibited significant antiproliferative and cytotoxic effects on HeLa229 cells, with higher selectivity towards cancer cells compared to normal cells. Moreover, wound healing assays showed the robust antimetastatic potential of AgNPs by inhibiting cancer cell migration. The real-time reverse transcription polymerase chain reaction analysis demonstrated the impact of AgNPs on inducing apoptosis and cell cycle arrest. Overall, these findings highlight the promising role of Ag-NPs synthesized from C. roseus extract as effective anticancer agents,offering a promising alternative to conventional chemotherapy with potentially reduced side effects and increased efficacy.

Pharmacological Effect of In Vitro Antioxidant Property and Green Synthesis of Silver Nanoparticles (AgNPs) Utilizing Murraya koenigii Antibacterial Application

ABSTRACT Background: Nonessential heavy metals pose a significant threat to human health due to their toxicity. Mercury, in particular, is identified as a hazardous metal. The study aims to detect mercury using colorimetric analysis with Murraya koenigii, emphasizing the eco-friendliness of the method. Aims and Objectives: The primary objective is to detect mercury using a colorimetric analysis method employing Murraya koenigii. Additionally, the study aims to investigate the eco-friendliness of this detection method. Materials and Methods: Colorimetric analysis was conducted using Murraya koenigii to detect mercury. Ultraviolet-visible (UV-vis) spectroscopy was employed to detect the formation of silver nanoparticles (AgNPs), with a characteristic surface plasmon resonance (SPR) band observed. X-ray diffraction (XRD) data analysis was performed to determine the crystalline nature and size of AgNPs. Scanning electron microscopy (SEM) was utilized to visualize the morphology of AgNPs. Fourier transform infrared (FTIR) spectroscopy was employed to identify functional groups involved in reducing silver ions. Antibacterial properties of synthesized AgNPs were tested against various microorganisms, including Escherichia coli, Staphylococcus aureus, Streptococcus mutans, and Enterococcus faecalis. Results: Mercury was successfully detected using colorimetric analysis with Murraya koenigii. Formation of AgNPs was confirmed by UV-vis spectroscopy, with a characteristic SPR band at 418 nm. AgNPs were found to be crystalline with an average size of 5.20 nm, as determined by XRD analysis. SEM images revealed spherical and polycrystalline AgNPs. FTIR spectra indicated the involvement of the -OH group of compounds in the extract in reducing silver ions. Synthesized AgNPs exhibited antibacterial properties against various microorganisms. Conclusion: A sustainable and eco-friendly method for synthesizing AgNPs using Murraya koenigii extract was successfully developed. This method not only detected mercury but also demonstrated antibacterial properties against various microorganisms. The study underscores the health implications of nonessential heavy metals, emphasizing the importance of eco-friendly detection and mitigation methods.

Selective Colorimetric Detection of Pb(II) Ions by Using Green Synthesized Gold Nanoparticles with Orange Peel Extract

Gold nanoparticles (AuNPs) were prepared by using a green approach that employed orange (citrus sinensis) peel water extract (OPE) as a reducing agent. In this case, the organic compounds present in orange peel were able to reduce Au(III) to Au(0) and, at the same time, to act as a capping agent, functionalizing the surface of the AuNPs, stabilizing them in a water solution. This “green” approach valorizes orange peel waste as a resourceful material and makes the synthetic process of AuNPs more environmentally sustainable, safe, and economically feasible than the traditional methods. The obtained gold nanoparticles (AuNPs@OPE) were characterized by FT–IR, DLS, SEM analysis, and UV–Vis spectroscopy; the latter showed a characteristic surface plasmon resonance (SPR) band at 530 nm, typical of spherical gold nanoparticles. The AuNPs@OPE were then tested as colorimetric sensors for heavy metals in water, showing an affinity and selectivity toward Pb2+. In fact, in the presence of Pb2+, the added cation favors the aggregation process, and, in this case, nanoparticles form clusters due to the interactions between Pb2+ and the carboxyl/hydroxyl groups on the surface of the AuNPs@OPE, increasing the size of the nanostructure. This process is accompanied by a change in color of the AuNPs@OPE from pink to violet, with a formation of a second, new SPR band, at a higher wavelength, relative to the aggregate formation. The colorimetric assay was tested at different times with the addition of Pb2+ ions showing different LOD values of 13.31 µM and 0.05 µM after 15 min and 90 min, respectively. The proposed colorimetric assay was also tested for analyzing Pb2+ in drinking water samples demonstrating the reliability to use AuNPs@OPE with real samples.

Insights into the impact of surfactants on the kinetics of selenium nanoparticles formation via lemon juice-assisted methodology, followed by their antibacterial and antioxidant assessment

Selenium nanoparticles (Se NPs) fabrication utilizing active species of natural lemon juice represents a promising pathway in the biosynthesis of nanoparticles. The reduction of Se4+ to Se(0) could be attributed to the presence of natural lemon juice, which was considered a supplier of vitamin C, polyphenolic compounds, flavonoids, and sugars. The synthesized spherical Se NPs exhibited a characteristic surface plasmon resonance band (SPR) at λ = 320 nm. The values of the rate constant for the reduction of Se (IV) to Se (0) by lemon juice were estimated to be kobs = 0.0011 s−1 for a Se concentration of 0.75 mmol.dm−3 and a lemon content of 0.001 mol.dm−3 at room temperature. Various conditions have been studied on the kinetics of Se NPs formation, such as the doses of SeO2 and lemon juice, and the presence of cationic and/or anionic surfactants like cetyltrimethyl ammonium bromide (CTABr) and sodium dodecyl sulfate (SDS), respectively. The synthesized Se particles were characterized by physicochemical techniques such as FT-IR, XRD, TEM, DLS, and zeta potential to investigate their main functional groups, crystallinity, chemical composition, particle size, and surface morphology. Moreover, the antioxidant power of Se NPs was tested in terms of their DPPH free radical scavenging activity. Finally, the antibacterial activity of the studied nanoparticles was confirmed against gram-positive and gram-negative bacteria (Staphylococcus aureus and Pseudomonas aeruginosa, respectively). In short, this study introduced the impact of surfactants on the formation of biocompatible Se NPs as an active antibacterial and antioxidant.

Development of silver nanocubes created by pulsed laser ablation in liquid

This paper describes a simple approach for creating silver (Ag) nanocubes using pulsed laser ablation in a liquid medium. The development of nanocubical formations of Ag obtained by laser ablation using Nd: YAG laser was conducted for 5, 10, 15, and 20[Formula: see text]min. The surface morphological analysis was performed using field-emission scanning electron microscopy (FESEM) to show the formation of silver nanocubes with edge lengths ranging from 150[Formula: see text]nm to 250[Formula: see text]nm. The UV-visible spectroscopy demonstrates that the concentration of Ag nanostructures, evidenced by the characteristic localized surface plasmon resonance band near 400[Formula: see text]nm in the colloidal solution containing Ag nanoparticles, increased with the increasing laser ablation duration from 5[Formula: see text]min to 20[Formula: see text]min. The growth mechanism for Ag nanocubes can be easily understood with the change in laser ablation time from 5 to 10, 15, and then 20[Formula: see text]min. The Ag sheets with no specific shape start to develop after 5 min of laser ablation, and after 10[Formula: see text]min, larger particles form. Then, after 15[Formula: see text]min, a small number of cube-like nanostructures with rough and uneven edges was obtained. At the end of 20[Formula: see text]min, a complete cubic formed with fine and distinct edges and a very large amount of nanocubes. The elemental silver signal was present in Ag nanocubes, as revealed by the energy-dispersive X-ray spectroscopy (EDS) spectra. The produced Ag nanocubes may be used to construct two-dimensional nanocomposites with practical applications in the electrical, optoelectronic, electrochemical, and biological areas.

Rapid colorimetric sensing of chlorpromazine HCl antipsychotic through in situ growth of gold nanoparticles.

Antipsychotic drugs like chlorpromazine hydrochloride (CPZ) are widely used to treat mental illnesses but can accumulate in the environment if not properly disposed of. Long-term exposure to trace levels of such pharmaceuticals may pose health risks. This study reports a colorimetric assay for detection of the antipsychotic drug chlorpromazine hydrochloride (CPZ) based on its ability to reduce gold ions and form gold nanoparticles (AuNPs). Optimization of reaction conditions such as pH, temperature and reagent concentrations enabled quantitative analysis of CPZ concentrations from 0.1-30 μg mL-1, with a detection limit of 0.06 μg mL-1, 0.23 μg mL-1 quantification limit and less than 3.5% RSD. The AuNPs exhibited a characteristic surface plasmon resonance band at 527 nm detectable by UV-vis spectrophotometry. Method validation with spiked serum, urine and environmental water samples demonstrated acceptable accuracy and precision. Interfering substances showed minimal impact, indicating resilience and specificity. This rapid, inexpensive colorimetric assay could facilitate environmental monitoring and biomedical analysis of antipsychotic drugs.

Synthesis, antimicrobial and antioxidant bioevaluation of silver nanoparticles using leaf extract of Sarcochlamys pulcherrima

In the present study, aqueous leaf extract of an underutilized vegetable Sarcochlamys pulcherrima was used to establish a straightforward, economical, and environmentally benign method for the synthesis of silver nanoparticles (AgNPs) with potent antioxidant and antibacterial activity. The synthesized AgNPs were characterized by UV-Vis spectroscopy, FT-IR spectroscopy, X-Ray diffraction (XRD)- and transmission electron microscopy (TEM) analysis. In the UV-Vis spectrum, the AgNP samples exhibited characteristic surface plasmon resonance band within 405–432 nm. The average crystallite size of the AgNPs calculated from the XRD data was found to be within the range of 15.6–25.6 nm. TEM analyses showed that most of the synthesised nanoparticles were spherical having dimensions in the range of 6–61 nm. The AgNPs exhibited significant antioxidant activity in the DPPH radical scavenging assay with a maximum of 89.12% inhibitory potential for the sample SP-8 and showed efficient anti-microbial potential against pathogenic bacterium Bacillus subtilis and Pseudomonas aeruginosa. The minimum inhibitory concentration (MIC) value of the sample SP-1 was found to be 0.78 μg/mL against P. aeruginosa which is at per with the MIC value of the standard neomycin (0.78 μg/mL). The minimum bactericidal concentrations (MBC) of the as-synthesized AgNPs for the selected bacterial strains were determined at concentrations of 25.0 μg/mL (B. subtilis) and 1.56 μg/mL (P. aeruginosa). This study concludes that the leaf extracts of the edible plant S. pulcherrima can be successfully utilised for convenient synthesis of AgNPs with antioxidant and antimicrobial potential.

Treatment of gastric cancer by silver nanoparticles encapsulated by chitosan polymers mediated by Pistacia atlantica extract under ultrasound condition

Abstract In this study, we prepared silver nanoparticles (AgNPs) employing ultrasound and chitosan (CS) in the presence of Pistacia atlantica aqueous extract as a non-toxic stabilizing and reducing agent for capping AgNPs with CS in a simple single-step process. The reduction of Ag+ ions into Ag0NPs was indicated by a visual transform in color. UV-Vis studies revealed that the characteristic surface plasmon resonance band appeared at around 460 nm. FT-IR, TEM, SEM, EDX, elemental mapping, XRD, and UV/Vis analytical methods were employed to characterize the AgNPs@CS nanocomposite. TEM study revealed nanoflowers-shaped NPs having various particle sizes. In the oncological part of this research, the status of normal and gastric cancer cell lines (MKN45, MKN28, NCI-N87, SNU-16, SNU-5, SNU-1, AGS, and KATO III) against the proposed nanomaterial were determined. The IC50 of AgNPs was 265, 304, 325, 127, 297, 318, 125, and 114 µg/mL against MKN45, MKN28, NCI-N87, SNU-16, SNU-5, SNU-1, AGS, and KATO III, respectively. It seems that the prepared NPs have stopped the growth of gastric cancer cells and the recent cancer cells have been removed with a high concentration of NPs. DPPH test results indicated removing 50% radicals by nanocomposite and butylated hydroxytoluene in the doses of 183 and 45 μg/mL.

Green synthesis of silver nanoparticles using Adhatoda vasica leaf extract and its application in photocatalytic degradation of dyes

The paper describes biogenic synthesis of silver nanoparticles (AgNPs) using Adhatoda vasica leaf extracts at room temperature. The prepared AgNPs were characterized by UV–visible spectroscopy, Fourier-transform infrared spectroscopy, powder X-ray diffraction, Energy dispersive X-ray (EDX), High Resolution Transmission Electron Microscope, Scanning Electron Microscopy and Thermogravimetric analyser. The bio reduction method is devoid of any toxic chemicals, organic solvents, and external reducing, capping and stabilizing agent. The synthesized AgNPs had spherical shape with particle size ranging between 3.88 and 23.97 nm and had face centered cubic structure. UV–visible spectral analysis confirmed the formation of AgNPs with a characteristic surface plasmon resonance band at 419 nm. The EDX pattern revealed the presence of elemental Ag in AgNPs. The prepared AgNPs were used for degradation of Amaranth, Allura red and Fast green in aqueous medium, with ≥ 92.6% efficiency within 15 min using 5 mg of AgNPs. The optical bandgap, Eg value of 2.26 eV for AgNPs was found to be effective for rapid photocatalytic degradation of all the three dyes. The degradation process was observed to follow pseudo first order kinetics.

Silk fibroin-based green colloidal silver nanoparticle synthesis and their antibacterial and anticancer properties

Aqueous silk fibroin (SF), derived from Bombyx mori silk, was used to synthesize colloidal silver nanoparticles (AgNPs) in situ under white light and at ambient temperature. A characteristic surface plasmon resonance (SPR) band at 425–435 nm from the UV–Vis spectrum provided evidence of the formation of AgNPs by UV–Visible spectroscopy. The nanoparticles that were synthesized were spherical with smooth surfaces, as evidenced by the transmission electron microscope (TEM) photographs. The size of the particles was between 35 and 40 nm. Additionally, X-ray diffraction (XRD) investigation supports the existence of silver's nanocrystalline phase with FCC crystal structure. The human bacterial pathogens Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) were significantly inhibited by the biogenic silver nanoparticles' antibacterial activity. The synthesized nanoparticles also show an excellent anti-cancer activity in lowest dosage.

Synthesis of Au NPs/Quince nanoparticles mediated by Quince extract for the treatment of human cervical cancer: Introducing a novel chemotherapeutic supplement

In this study, we have prepared mono-dispersed gold nanoparticles using the aqueous extract of Quince. The effective phytocompounds in the extract carried out the function as both reducing and stabilizing agents in the synthesis of Au NPs. The reduction of Au3+ ions into Au0 NPs was indicated by a visual transform in color from pale yellow to deep red. UV-Vis studies revealed the characteristic surface plasmon resonance band appeared at around 545 nm. FT-IR, TEM, SEM, EDX, XRD, and UV/Vis analytical methods were employed to characterize the Au NPs/Quince nanocomposite. TEM study revealed globular shaped NPs having particle size around 20–30 nm. Towards its biological implication, MTT method was followed in order to survey the cytotoxicity and inhibition of human cervical cancer against Hela, SiHa, and CCI-PI 19 cell lines and the corresponding IC50 values were evaluated as 465, 712, and 785 μg/mL respectively. The % cell viabilities diminished dose-dependently over the bio-nanomaterial. To survey the antioxidant properties of Au NPs/Quince, DPPH assay was used and here the related IC50 value was determined as 72 μg/mL.

Optimization of biosynthesis zinc oxide nanoparticles: Desirability-function based response surface methodology, physicochemical characteristics, and its antioxidant properties

The optimization of zinc oxide nanoparticles (ZnO NPs) with maximum yield and smaller particle size synthesized using cell-free supernatant (CFS) of Lactobacillus plantarum TA4 were investigated using a desirability-function based response surface methodology (RSM). A central composite rotatable design (CCRD) with five levels and three factors namely zinc concentration (200-500 mM), pH (6-10), and CFS volume ratio (20-50%) were employed to study the response variables. A total of 20 experimental runs were performed and desirability-function showed that the optimal conditions for the maximum yield and minimum particle size were 352.4 mM of Zn concentration, pH 9, and 25 % of CFS volume ratio. At these optimal conditions, the predicted yield and size of the optimized ZnO NPs were 2.47 g and 75.8 nm, respectively. The validation test showed 2.41 g of yield and an average size of 80.5 nm. The UV-Vis spectroscopy showed the characteristic surface plasmon resonance band (SPR) at an absorption peak of 360 nm, confirming the formation of optimized ZnO NPs. Dynamic light scattering (DLS) demonstrated the small hydrodynamic size and low polydispersity index (PDI) of ZnO NPs at 85.9 nm and 0.243, respectively. A high-resolution transmission electron microscope (HRTEM) analysis illustrated spherical and oval-shaped ZnO NPs with an average particle size of 29.7 nm. Furthermore, Fourier-transform infrared (FTIR) analysis showed that biological compounds (proteins, enzymes, and carbohydrates) from CFS were involved in the reduction and capping of ZnO NPs. Raman spectroscopy and thermogravimetric analysis (TGA) demonstrated the crystallinity and thermal stability of ZnO NPs. Furthermore, the total antioxidant capacity (TAC) and free radical scavenging activity (RSA) of ZnO NPs demonstrated promising antioxidant properties when compared to their bulkier counterparts. Overall, this work paves the way for a cleaner and environmentally friendly production of ZnO NPs for industrial use.

Silver nanoparticle-conjugated antibiotics inhibit in vitro growth of Brucella melitensis.

Background and Aim:Brucellosis is a contagious livestock disease with a significant economic impact. This study aimed to compare the efficacy of antibiotics used alone or in combination with silver nanoparticles (AgNPs) against Brucella melitensis Rev 1 in vitro.Materials and Methods:AgNps conjugated with ciprofloxacin was synthesized and thoroughly characterized by ultraviolet visible spectrophotometry (UV-vis). The antimicrobial effect of ciprofloxacin alone and ciprofloxacin conjugated with AgNPs against B. melitensis Rev 1 was determined by minimum inhibitory concentration (MIC) and the erythrocyte hemolytic assay determined the capability of conjugation to cause hemolysis in human erythrocyte.Results:The UV-vis spectra of both silver-drug nanoconjugates showed a characteristic surface plasmon resonance band at 420 nm. The MIC assays showed that AgNPs conjugation to antibiotics enhanced the antibacterial potential of the selected antibiotics against B. melitensis Rev 1 relative to non-conjugated antibiotics. The results show that low concentrations of AgNPs can kill B. melitensis Rev 1. The MICs of ciprofloxacin and ciprofloxacin–AgNPs were 0.75 and 0.05 μM, respectively.Conclusion:The conjugation of ciprofloxacin with AgNPs enhanced the antibacterial effects against B. melitensis Rev 1. In addition, this conjugation appears to inhibit the capability of this bacterium to adapt to the presence of antibiotics, thereby inhibiting bacterial resistance. Further studies are required to examine its potential as an in vivo treatment.

Hydrogel assisted synthesis of gold nanoparticles with enhanced microbicidal and in vivo wound healing potential

The present study reports a hydrogel-based sunlight-assisted synthesis of gold nanoparticles (Au NPs) with enhanced antimicrobial and wound healing potential. The hydrogel extracted from the seeds of Cydonia oblonga was used as a reducing and capping agent to synthesize Au NPs for the first time. The as-synthesized Au NPs were characterized for an average size, shape, surface functionalization, antimicrobial, and wound healing capabilities. The cubic and rectangular-shaped Au NPs with an average edge length of 74 ± 4.57 nm depicted a characteristic surface plasmon resonance band at 560 nm. The hydrogel-based Au NPs inhibited the growth of microorganisms in zones with 12 mm diameter. In-vitro experiments showed that a minimum inhibitory concentration of Au NPs (16 µg/mL) was sufficient to mimic the 95% growth of pathogenic microorganisms in 24 h. In vivo treatment of wounds with Au NPs in murine models revealed a 99% wound closure within 5 days. Quantitative PCR analysis performed to decipher the role of Au NPs in enhanced wound healing showed an increase in the expression levels of NANOG and CD-34 proteins.

The interaction mechanism between gold nanoparticles and proteins: Lysozyme, trypsin, pepsin, γ-globulin, and hemoglobin

In this study, the interaction between gold nanoparticles (AuNPs) and proteins (including lysozyme, trypsin, pepsin, γ-globulin and hemoglobin) was investigated by UV–visible absorption spectroscopy, fluorescence spectroscopy, circular dichroism (CD) spectroscopy and protein activity assay. AuNPs was synthesized using reduction of HAuCl4 with sodium citrate. The formation of AuNPs was confirmed from the characteristic surface plasmon resonance band at 521 nm and transmission electron microscopy revealed the average particle size was about 10 nm. The results reveal that AuNPs can interact with proteins to form a “protein corona (PC)”, but the protein concentration required to form a relatively stable PC is not the same. The quenching mechanism of proteins by AuNPs is arisen from static quenching. The binding constants of AuNPs with proteins are in the range from 106 to 1010 L mol−1, and the order is pepsin > γ-globulin > hemoglobin > trypsin > lysozyme at 298 K. Van der Waals forces and hydrogen bonds are the main forces for the lysozyme-AuNPs system. The interaction between trypsin/pepsin/γ-globulin/hemoglobin and AuNPs is mainly by hydrophobic interaction. The addition of AuNPs has an effect on the secondary structure of proteins as confirmed from CD spectra. The change in secondary structure of different proteins is different and seems to have little relation with the binding constant. The activity of lysozyme/trypsin/pepsin decreases with the addition of AuNPs.

A sensitive colorimetric nanoprobe based on gold nanoparticles functionalized with thiram fungicide for determination of TNT and tetryl

Water and soil pollution (especially by explosive residues) is a global environmental problem, and tackling with this problem involves the selective and sensitive development of analytical techniques for trace explosives detection. In this regard, a gold nanoparticles (AuNPs)-based colorimetric probe was developed for the determination of TNT and tetryl as nitro-explosives. Au-nanoparticles were synthesized and their surface was modified with a fungicide, tetramethylthiuram disulfide (thiram), having both Au-anchoring S-atoms and TNT/tetryl ligating tert-amine groups as charge donors. The prepared probe (AuNPs@Thr) rapidly aggregated as a result of donor–acceptor (D-A) interaction between the amine group of thiram and the nitro-groups of explosives (TNT and tetryl), resulting in a bathochromic shift in the characteristic surface plasmon resonance band of AuNPs@Thr. Detection and quantification limits (LOD and LOQ) for TNT and tetryl were found as 5 and 15 ppb (µg L-1), respectively. Common soil ions (Cd2+, Fe3+, Fe2+, Mn2+, Zn2+, Mg2+, Cu2+, Al3+, Co3+, Ca2+, K+, Na+, Cl-, NO3–, SO42-, NO2–, and CO32–) did not interfere, and the explosive mixtures (comp B, synthetic comp B, and tetrytol) having TNT and tetryl constituents could be effectively analyzed with the proposed method. The method was validated against the reference LC–MS/MS method, applied to sandy soil samples contaminated with TNT and tetryl. Thiram as AuNPs − modifier was much cheaper than other aminothiols for probe manufacture, but could compete with them with respect to selectivity and sensitivity of nitro-explosives assay.

SDS capped Cu nanorods: photosynthesis, stability, and their catalytic activity for trypan blue oxidative degradation

Sodium dodecyl sulfate (SDS) capped- Cu nanorods were prepared by using ascorbic acid under light limiting diode (LED) irradiation for the first time. The preliminary indications of CuNPs production were the appearance of yellow (Cu2O) and red-chocolate color (Cu0) in absence and presence of LED exposure at room temperature. The optical, spectroscopic and morphological properties of as-prepared NPs were characterized using UV–visible spectroscopy through the presence of a characteristic surface Plasmon resonance (SPR) band for Cu0 at 584 nm along with high absorbance at 800 nm for Cu2O. X-ray diffraction (XRD) shows that the red-chocolate color consist 90% metallic Cu0 and 9.7% Cu2O with face cubic center unit cell structure of CuNPs. Transmission electron microscope (TEM), energy dispersive X-ray (EDX), and scanning electron microscope (SEM) revealed that the CuNPs were nano-rods with an average length ranging from 300 to 350 nm. LED light assisted degradation of trypan blue (TB) was also investigated in presence of CuNPs and K2S2O8. The existence of sulfate radicals (SO4-•) and hydroxly radicals (HO•) generated during the degradation were identified by using different radical scavengers. Degradation follows first-order kinetics with respect to K2S2O8 concentrations. The oxidative dissolution of CuNPs was also observed along with the TB degradation. Based on the absorbance changes at 590 nm, the degradation and dissolution mechanisms were proposed and discussed.

Role of Synthetic Plant Extracts on the Production of Silver-Derived Nanoparticles.

The main antioxidants present in plant extracts—quercetin, β-carotene, gallic acid, ascorbic acid, hydroxybenzoic acid, caffeic acid, catechin and scopoletin—are able to synthesize silver nanoparticles when reacting with a Ag NO3 solution. The UV-visible absorption spectrum recorded with most of the antioxidants shows the characteristic surface plasmon resonance band of silver nanoparticles. Nanoparticles synthesised with ascorbic, hydroxybenzoic, caffeic, and gallic acids and scopoletin are spherical. Nanoparticles synthesised with quercetin are grouped together to form micellar structures. Nanoparticles synthesised by β-carotene, were triangular and polyhedral forms with truncated corners. Pentagonal nanoparticles were synthesized with catechin. We used Fourier-transform infrared spectroscopy to check that the biomolecules coat the synthesised silver nanoparticles. X-ray powder diffractograms showed the presence of silver, AgO, Ag2O, Ag3O4 and Ag2O3. Rod-like structures were obtained with quercetin and gallic acid and cookie-like structures in the nanoparticles obtained with scopoletin, as a consequence of their reactivity with cyanide. This analysis explained the role played by the various agents responsible for the bio-reduction triggered by nanoparticle synthesis in their shape, size and activity. This will facilitate targeted synthesis and the application of biotechnological techniques to optimise the green synthesis of nanoparticles.