Presence Of Nitrate Ions Research Articles

Dimerization of Fe(III) Ion in an Aqueous Medium: Mechanistic Modelling and Effects of Ligands.

Aqueous iron solutions generally undergo spontaneous hydrolysis followed by aggregation resulting in the precipitation of nanocrystalline oxyhydroxide minerals. The mechanism of nucleation of such multinuclear oxyhydroxide clusters are unclear due to limited experimental evidence. Here, we investigate the mechanistic pathway of dimerization of Fe(III) ions using density functional theory (DFT) in aqueous medium considering effects of other ligands. Two hydrolyzed monomeric Fe(III) ions in aqueous medium may react to form two closely related binuclear products, the μ-oxo and the dihydroxo Fe2 dimer. Our studies indicate that the water molecules in the second coordination sphere and those co-ordinated to the Fe(III) ion, both participate in the dimerization process. The proposed mechanism effectively explains the formation of dihydroxo and μ-oxo Fe2 dimers with interconversion possibilities, for the first time. Results show, with only water molecules present in the second co-ordination sphere, dihydroxo Fe2 dimer is the thermodynamically and kinetically favored product with a low activation free energy. We calculated the step-wise reaction free energies of dimerization in the presence of nitrate ions in the first and second coordination sphere of Fe(III) ion separately, which shows that with nitrate ions in the second co-ordination sphere, the μ-oxo Fe2 dimer is the kinetically favored product.

Enhancing Nitrate Ion Removal from Water using Fixed Bed Columns with Composite Chitosan-based Beads

Water contamination is a pressing global concern, especially regarding the presence of nitrate ions. This research focuses on addressing this issue by developing an effective adsorbent for removing nitrate ions from aqueous solutions. two adsorbents Chitosan-Zeolite-Zirconium (Cs-Ze-Zr composite beads and Chitosan-Bentonite-Zirconium Cs-Bn-Zr composite beads were prepared. The study involved continuous experimentation using a fixed bed column with varying bed heights (1.5 and 3 cm) and inlet flow rates (1 and 3 ml/min). The results showed that the breakthrough time increased with higher bed heights for both Cs-Ze-Zr and Cs-Bn-Zr composite beads. Conversely, an increase in flow rate led to a decrease in breakthrough time. Notably, Cs-Ze-Zr and Cs-Bn-Zr demonstrated impressive removal efficiencies, reaching 87.23% and 92.02%, respectively. The optimal conditions for peak performance were found to be an inlet flow rate of 1 ml/min, a bed height of 3 cm, and initial concentrations of 400 mg/L and 600 mg/L for Cs-Ze-Zr and Cs-Bn-Zr, respectively.

Anion-Driven Nanostructuring of Copper Electrodeposits for Tuning the Selectivity of Electrocatalytic CO2 Reduction Reaction

Electrochemical CO2 reduction (ECR) to value-added products is one of the potential ways to utilise CO2 as a feedstock, thereby decreasing its level in the atmosphere as it has harmful repercussions on planet earth. Copper (Cu)-nanostructures have demonstrated a great potential to convert CO2 into valuable higher-end hydrocarbons electrochemically, but with poor selectivity1. Therefore, novel strategies to tune Cu-based electrocatalysts' activity and selectivity toward multi-carbon products, particularly at low overpotential, are highly desirable. At the same time, keeping in mind the growing concerns regarding the environmental impact of the synthetic procedures and atom-economy among chemists, the synthesis methods employing reagents with multiple characteristics are equally essential to ensure minimal use of undesirable and excess reagents. In the present work, we report an atom-economic strategy to tune the physicochemical properties and the electrocatalytic activity of Cu-nanostructures towards ECR. The Cu-nanostructures namely CA, CN, CS and CC were synthesized via pulse electrodeposition from an electrolyte bath containing Cu-precursor salts with varying anions viz. acetate, nitrate, sulphate, and chloride respectively and are investigated for the effect of anions on the physicochemical properties and ECR performance. In the case of Cu electrodeposition process, when the pH is low as in the case of sulphate and acetate ions, electrodeposition is accompanied by hydrogen evolution reaction2 which results in the formation of nondendritic structures as in the case of CS and CA. But the presence of nitrate ions in the electrolyte bath causes nitrate reduction reaction to take place as a side reaction as well, as Cu is a well-known catalyst for nitrate reduction. Thus, this simultaneous redox reaction at the surface of the Cu electrodeposit causes an additional dissolution of the Cu nuclei3. This results in a smoother morphology as seen in CN as the dendrite formation is overridden. The very distinct cubic morphology of CC is due to Chloride ions in the bath.The presence of chloride ions during the electrodeposition of CC samples results in the formation of nanocubes by reducing Cu2+ via the formation of CuCl which is known to exist in cubic form when it precipitates4. The intermediate CuCl then quickly forms Cu2O through an equilibrium reaction in the presence of H2O when the concentration of chloride ions is not so high. The Cu-nanostructures electrodeposited from Cu-chloride demonstrated the best ECR performance with the highest total faradaic efficiency for carbon products and good selectivity for ethylene formation (30% at -0.93V vs RHE). The presence of chloride ions in the electrolyte bath strongly affects the active sites of the Cu deposits as the cubic morphology of CC catalyst exposes large number of Cu (100) faces5. Cu (100) are highly selective towards ethylene formation with very low overpotential due to the lower barrier for Cu-CO* which leads to greater CO coverage favouring CO*-CO* coupling at low bias59. In addition to that the electrochemically active surface area, the higher Cu+ content can be rationalized as the reasons for relatively higher ECR activity of CC.

Changes in nitrate binding with lanthanides in BLPhen complexes

Preorganized ligands such as bis-lactam-1,10-phenanthroline (BLPhen) offer unique selectivity trends in solvent extraction of rare-earth ions, particularly from aqueous nitrate solutions. However, due to the ligand’s lipophilicity it is experimentally challenging to obtain crystal structures of the corresponding lanthanide (Ln):ligand complexes to describe the local structure of the first coordination shell and the role of the nitrate ions in the organic phase. Herein, we report first principles molecular dynamics (FPMD) simulations of the complexation of trivalent lanthanide ions (La, Nd, and Eu) with the BLPhen ligand in the presence of nitrate ions in the dichloroethane (DCE) solvent. We find that two nitrate anions are present in the first solvation shell and the third nitrate anion is far from the first solvation shell in all three [Ln(BLPhen)2]3+ complexes examined. Moving along the lanthanide series from La to Nd to Eu, the binding pocket formed by the two BLPhen ligands shrinks in size; as a result, the two nitrate configuration changes from one-monodentate/one-bidentate binding mode for La and Nd to all monodentate for Eu. Meanwhile, the total coordination number drops from 11 for La and Nd to 10 for Eu. More interestingly, the bidentate binding in [La(BLPhen)2]3+ and [Nd(BLPhen)2]3+ complexes is highly dynamic, frequently switching to monodentate and back. The FPMD insights into the differing modes and dynamics of nitrates in the first coordination shell will be useful for further atomistic understanding of the complex structure, formation, and stability in the organic phase.

A Highly Selective and Sensitive Sequential Recognition Probe Zn2+ and H2PO4- Based on Chiral Thiourea Schiff Base.

A series of novel chiral thiourea fluorescent probes HL1-HL6 were designed and synthesized from (1R,2R)-1,2-diphenylethylenediamine, phenyl isothiocyanate, and different substituted salicylic aldehydes. All of the compounds were confirmed by 1H NMR, 13C NMR, and HRMS. They exhibit high selectivity and sensitivity to Zn2+ in the presence of nitrate ions with the detection limit of 2.3 × 10-8 M (HL5). Meanwhile, their zinc (II) complexes (L-ZnNO3) showed continuous response to H2PO4- in acetonitrile solution. The identification processes could further be verified by supramolecular chemistry data analysis, X-ray single-crystal diffraction analysis, and theoretical study. The research provides reliable evidence for an explanation of the mechanism of action of thiourea involved in coordination, which is important for the application of thiourea fluorescent probes. In short, the sensors HL1-HL6 based on chiral thiourea Schiff base will be promising detection devices for Zn2+ and H2PO4-.

Nitrate Reduction By Hydrophobic, Negatively, and Positively Charged Peptide-Coated Au Electrode

Nitrate has been considered as a source of water pollution with harmful effects on human health. Compared to other removal techniques, electrochemical reduction of nitrate is capable of delivering products such as ammonia and nitrogen which are valuable and harmless, respectively. However, it is challenging to control nitrate reduction pathway through catalyst design alone. Our research goal in this work is to understand how peptide chemistry influences nitrate reduction pathway and electrocatalyst activity for a suite of peptide-functionalized electrocatalyst surfaces. To analyze the electrocatalytic reduction of nitrate, three types are peptides, including V (hydrophobic), E (negatively charged), and K (positively charged), were coated on the gold electrodes and their performance compared with the bare gold electrode. In all the experiments, the effective area of the Au electrode was 1 cm2. An electrochemical cell with the gold electrode (working electrode), platinum (counter electrode) electrode, and a background solution (0.5 M Na2SO4) were used for electrochemical experiments. Cyclic voltammetry (CV) was used to assess the reduction of nitrate by different peptide-coated Au electrodes in the presence of nitrate ions (0.5 M Na2SO4 +0.1 M NaNO3, pH∼7.1), with a scanning rate of 20 mV/s. Chronoamperometry (CA) was applied to investigate the conversion of nitrate to different products and the pathway of nitrate reduction at different operational conditions. UV–visible spectrophotometry was employed to analyze the conversion of nitrate into nitrite and ammonia in the solution. Results of CV indicate that gold electrodes coated with V and E type peptides have promising responses to the applied voltage in the presence of nitrate ions. Based on the results, reduction of nitrate takes place at the onset potentials of -0.37 V and -0.23 V versus reversible hydrogen electrode (RHE) for E and V types of peptide-coated Au electrodes, respectively. To assess the pathway of nitrate reduction, CA experiments were done for 60 minutes on the hydrophobic peptide-coated Au and bare Au electrodes by applying a constant potential of -0.37 V versus RHE. Initial CA results of the V peptide coated-Au electrode indicate the reduction of nitrate into both nitrite and ammonia compared to a bare gold electrode which is only capable of nitrate reduction to ammonia. Based on the initial results, 0.92 mg ammonia, and 0.78 mg nitrite were produced by a V-type coated-Au electrode after 60 minutes CA experiment.

Inorganic Ions Enhance the Number of Product Compounds through Heterogeneous Processing of Gaseous NO2 on an Aqueous Layer of Acetosyringone.

Methoxyphenols represent important pollutants that can participate in the formation of secondary organic aerosols (SOAs) through chemical reactions with atmospheric oxidants. In this study, we determine the influence of ionic strength, pH, and temperature on the heterogeneous reaction of NO2 with an aqueous film consisting of acetosyringone (ACS), as a proxy for methoxyphenols. The uptake coefficient of NO2 (50 ppb) on ACS (1 × 10-5 mol L-1) is γ = (9.3 ± 0.09) × 10-8 at pH 5, and increases by one order of magnitude to γ = (8.6 ± 0.5) × 10-7 at pH 11. The lifetime of ACS due to its reaction with NO2 is largely affected by the presence of nitrate ions and sulfate ions encountered in aqueous aerosols. The analysis performed by membrane inlet single-photon ionization-time-of-flight mass spectrometry (MI-SPI-TOFMS) reveals an increase in the number of product compounds and a change of their chemical composition upon addition of nitrate ions and sulfate ions to the aqueous thin layer consisting of ACS. These outcomes indicate that inorganic ions can play an important role during the heterogeneous oxidation processes in aqueous aerosol particles.

Photodegradation of an Anilide Fungicide Inpyrfluxam in Water and Nitrate Aqueous Solution.

The photodegradation behavior of a new anilide fungicide, inpyrfluxam [3-difluoromethyl-N-[(R)-2,3-dihydro-1,1,3-trimethyl-1H-inden-4-yl]-1-methylpyrazole-4-carboxamide] (1), was investigated in aqueous buffer and nitrate solutions under irradiation with artificial sunlight (λ > 290 nm). In both media, 1 mainly photodegraded via oxidation at the 3'-position of the Indane ring, cleavage of the C-N bond of the amide linkage and N-phenyl ring bond, and finally mineralization to carbon dioxide. No isomerization of 1 occurred at the 3'-position of the Indane ring. In the presence of nitrate ion, which originates from fertilizer in agricultural fields, the degradation of 1 was significantly accelerated as compared with buffer solution, and the reaction rate was strongly correlated with the concentration of hydroxyl radicals derived from the photolysis of nitrate ions. The reaction rate constant of hydroxyl radicals with 1 was determined to be 3.0 × 1010 /M/s, which was higher than that of hydroxyl radicals with other pesticides possessing aromatic rings.

Magnetic field‐assisted photochemical oxidation of benzyl alcohol to corresponding aldehydes by introducing TiO2(P25)‐ZnO/Fe3+ as a novel nanophotocatalyst

AbstractFor the first time, the surface modification of nanophotocatalyst TiO2(P25)‐ZnO was reported by the introduction of Fe3+ for modulation of the photocatalytic activity. The nanophotocatalyst TiO2(P25)‐ZnO/Fe3+ was synthesized and its crystal structure, morphology, and photocatalytic activity were well determined by, diffuse reflectance spectroscopy, energy dispersive X‐ray, X‐ray diffraction, and scanning electron microscope analyses. The photocatalyst was applied for the selective oxidation of different aryl alcohols to the respective aldehyde beneath visible light (blue LED lamp, λ > 420 nm) in the presence of nitrate ion as oxidant. Also, for the first time, the effect of presence of an external magnetic field (5,000 G) contemporary with photoreaction was studied simultaneously by applying an external magnet field of 5,000 G and valuable results were obtained so that the time of photoreaction declined considerably up to 65%. This study has many advantages like the use of a magnetic field as a green technology, being clean, and zero energy. Also, the photoreaction did stop at the stage of aldehyde to provide a considerable selectivity.

Ionic strength effect on the formation of organonitrate compounds through photochemical degradation of vanillin in liquid water of aerosols

The ionic strength can affect the photochemical reactions occurring in the liquid core of the aerosol deliquescent particles. Yet, the investigations related to ionic strength effect on aqueous-phase reactions are limited. Here we assess the photochemical degradation of a typical lignin-derived compound, vanillin (VL), upon addition of either sodium nitrate (NaNO3) or sodium sulfate (Na2SO4). The UV-VIS absorption spectra of VL exhibits a hyperchromic effect and a bathochromic shift of the n→π* absorption band, in going from λmax = 310 nm in the dilute aqueous phase to λmax = 346 nm at I = 0.3 M adjusted by Na2SO4. A hypsochromic shift of the n→π* absorption band of VL, in going from λmax = 310 nm in the dilute liquid water to λmax = 303 nm at Ieff = 0.124 M is observed when the ionic strength was adjusted with NaNO3.At fixed pH ≈ 4, representing both the cloud droplets and the liquid core of the aerosol particles, the pseudo-first-order rate constant, k1st (Ieff.→0) = (1.5 ± 0.2) x 10−5 s−1, in dilute aqueous solution (Ieff = 0 M, NaNO3), linearly decreases to (k1st = (3.7 ± 0.2) x 10−6 s−1), at Ieff = 0.124 M (NaNO3) with kinetic salting coefficient b = -(4.8 ± 0.2) L mol−1. The very subtle pH change of the absorption spectra of irradiated VL is observed due to the formation of carboxylic acids, hydroxylated compounds and oligomers which presence was confirmed by FT-ICR MS analysis. Most likely aliphatic like CHO compounds are formed upon photodegradation of VL in dilute aqueous phase while the condensed aromatic CHO and CHON compounds are produced in presence of nitrate ions (Ieff = 0.124 M). These results suggest that inorganic ions present in the liquid water of aerosols alters the kinetics and the product formation of photochemical degradation of organic compounds which in turn can affect the light absorption properties of aerosols.

Biodegradation of catechol by Pseudomonas fluorescens isolated from petroleum‐impacted soil

AbstractBioremediation strategies have been applied to clean up petroleum hydrocarbon (PHC) impacted sites. Introducing PHC degrading microorganisms (bioaugmentation) and enhancing the in‐situ nutrients availability (biostimulation) are widely used strategies. These strategies can be combined to lead to a better bioremediation performance. In this work, Pseudomonas fluorescens was isolated from a PHC impacted site. Through a 23 factorial design plan, the effect of various combinations of nitrate, sulphate, and phosphate ions on the PHC bioremediation performance by P. fluorescens was investigated using catechol, an essential metabolic intermediate of BTEX degradation, as the sole carbon source. The maximum specific catechol degradation rate was chosen as the response to evaluate the catechol bioremediation performance. The ANOVA results indicated that the presence of nitrate ions alone lowered the maximum specific catechol degradation rate, which can be explained by the accumulation of nitrites and ammonia during the denitrification process by P. fluorescens. It was noted that dosing sulphate ions alone did not affect the bioremediation performance, which indicates P. fluorescens can grow in a sulphur‐limited environment. In contrast, the presence of sulphate and nitrate ions together can lead to a higher specific catechol degradation rate. This may be caused by the presence of sulphate that can suppress the production of nitrites. The importance of phosphate ions on catechol biodegradation was investigated. The absence of phosphate led to incomplete biodegradation. Introducing phosphate ions can accelerate catechol degradation, which can be explained by the secretion of organic acids.

Nitrate Radical Facilitates Indirect Benzyl Alcohol Oxidation on Bismuth(III) Vanadate Photoelectrodes

AbstractBismuth(III) vanadate (BiVO4) films show activity for direct benzyl alcohol (PhCH2OH) oxidation to benzaldehyde (PhCHO) in acetonitrile solvent. Introducing tetrabutylammonium nitrate (Bu4NNO3) drastically reduces the overpotential required to generate the PhCHO product while maintaining a high faradaic efficiency (FE) >90 %. BiVO4 corrosion accompanies PhCH2OH oxidation. However, the presence of nitrate ions (NO3−) results in significantly less bismuth‐ and vanadium‐ion leaching (determined by ICP‐MS analysis), as well as reduced surface roughening (determined by SEM imaging). In this reaction, it is proposed that rate‐determining NO3− oxidation generates a highly reactive nitrate radical (NO3⋅) that reacts with PhCH2OH by hydrogen‐atom abstraction (HAT). NO3− is stoichiometrically consumed by the irreversible formation of electrochemically inert HNO3, characterized by an ECi mechanism, rather than a catalytic EC′ mechanism. In the presence of PhCH2OH, NO3− oxidation on BiVO4 becomes more facile; every order of magnitude increase in PhCH2OH concentration shifts the NO3−/ NO3⋅ equilibrium potential negatively by 200 mV. The shift results from the introduction of a consumption pathway for the nitrate radical intermediate via a coupled chemical step with benzyl alcohol. This report is the first example of photoelectrochemical NO3⋅ generation to initiate indirect PhCH2OH oxidation.

The determination of the nitrogen-containing ions concentrations dynamics in the oxbow of Ishimchik to assess the impact of 2016–2017 floods

This paper presents the results of the ecological state study of oxbow Ishimchik, located in Ishim, Tyumen Region. The paper presents data on the nitrogen-containing ions concentrations dynamics in water samples of oxbow Ishimchik over the summer-autumn of 2017, the content of which is an important indicator of the water chemical composition. The presence of nitrate ions, nitrite ions and ammonia in high concentrations in the samples usually indicates that the reservoir suffers from contamination by household, agricultural and industrial waste. In 2016 and 2017 a large amount of water from heavy floods came to the oxbow, which could significantly increase the concentration of mineral forms of nitrogen. The main concern is the flood of 2016 as to stop the Ishim private sector flooding a channel was dug for discharge of floodwaters from the town-affected part into the oxbow. To determine the content of nitrogen-containing ions, the photometry method was used. The results of a chemical analysis show that the content of ammonium and ammonia cations (total), nitrite anions and nitrate anions is less than maximum permissible concentration as well as there is a change in the prevailing mineral form of nitrogen from redoxidized to oxidized.

Operando Studies of the Electrochemical Dissolution of Silver Nanoparticles in Nitrate Solutions Observed With Hyperspectral Dark-Field Microscopy.

Since nanoparticles are frequently used in commercial applications, there is a huge demand to obtain deeper insights into processes at the nanoscale. Especially, catalysis, chemical and electrochemical reaction dynamics are still poorly understood. Thus, simultaneous and coupled opto-and spectro-electrochemical dark-field microscopy is used to study in situ and operando the electrochemically driven dissolution mechanism of single silver nanoparticles in the presence of nitrate ions as non-complexing counter-ions, herein. Hyperspectral imaging is used to probe the intrinsic localized surface plasmon resonance of individual silver nanospheres before, during and after their electrochemical oxidation on a transparent indium tin oxide (ITO) electrode. Furthermore, optical video imaging was performed for additional information. Based on the complete loss of spectral information and intensity, a dissolution of the particles during the reaction was concluded. This way it is revealed that the dissolution of individual particles proceeds over several seconds, indicating a hindrance by the nitrate ions. Only electrochemical analysis does not provide this insight as the measured current does not allow distinguishing between successive fast dissolution of one particle after another or slow dissolution of several particles in a concerted manner. For comparison, experiments were performed in the presence of chloride ions. It was observed that the silver chloride formation is an instantaneous process. Thus, it is possible to study and define the reaction dynamics on the single nanoparticle level in various electrochemical systems and electrolyte solutions. Accordingly, operando opto- and spectro-electrochemical studies allow us to conclude, that the oxidation of silver to solvated silver cations is a kinetically slow process, while the oxidation to silver chloride is fast. We propose this approach as a new method to study electrocatalyst materials, their transformation and degradation under operando conditions.

Liquid-liquid extraction of Co(II) from nitrate solution using TOA

Cobalt has widespread industrial applications but if present in excess amounts it may cause several noxious effects. Liquid-liquid extraction process can be useful in cleaning the environment from harmful chemical pollutants. Solvent extraction of cobalt using cobalt nitrate as the feed solution and trioctylamine (TOA) as the extractant in toluene was carried out where the effects of nitric acid concentration, equilibration time, concentration of the extractant and cobalt ions had been investigated. The percentage extraction of Co(II) decreased upon increasing the concentration of acid. A time of 15 min was needed to achieve the extraction equilibrium. Highest percentage extraction of cobalt was achieved using 0.1 M TOA which is 99%. Cobalt loading increased with increase in metal ion concentration. Presence of nitrate ions had almost no significance in the extraction process. The loaded organic phase was stripped using different stripping agents and 99.15% back extraction was achieved with 0.1 mol/L (NH4)2CO3. The extraction mechanism was proposed from the FTIR and slope measurement.

Nitrate Ion-Incorporated Stable Perovskite Nanocrystals by a Solvent-Free Mechanochemical Reaction.

We have synthesized a new class of organolead halide perovskite nanocrystals by a solvent-free mechanochemical green approach. We have developed a new combination of precursor by incorporating nitrate ions into the MAPbBr3 perovskite core. While the presence of nitrate ion is evidenced by Fourier-transform infrared spectra, X-ray diffraction data shows the formation of perovskite nanocrystals. By altering the precursor composition, the morphology of the nanocrystals changes. Photoluminescence properties of these nanocrystals are preserved. Moreover, the stability of these nanocrystals is monitored for a long time, which shows that the incorporation of nitrate ions into the perovskite nanocrystal core does not have any decremental effect on its stability. Nonetheless, this strategy to synthesize perovskite nanocrystals reduces the solvent toxicity.

Photolytic quorum quenching: A new anti-biofouling strategy for membrane bioreactors

Microbial quorum sensing induces biofilm formation on the membrane filter leading to severe biofouling. Here we show the novel observation and efficacy of long-wave UV photolysis as it interferes with microbial quorum sensing, particularly investigating anti-biofouling performances in membrane bioreactor systems. Continuous UV radiation significantly mitigated membrane biofouling, even more efficiently than bacterial quorum quenching achieved by the quorum quenching bacterium Rhodococcus sp. BH4. Intermittent UV photolysis had less quenching efficacy; it was, however, just as efficient as bacterial quorum quenching given an optimum UV dose. Indirect photolytic inactivation of signal molecules, such as acylhomoserine lactones and autoinducer-2, possibly occurred due to reactive oxygen radicals produced in the presence of nitrate ions. UV photolysis can be a new tool to inhibit microbial group behaviors (e.g., biofouling) occurring in membrane bioreactors and other biosystems.

Mechanism of formation of adsorption complexes amikacin–detonation nanodiamond

The adsorption of amikacin on the surface of detonation nanodiamonds was revealed as proceeding via the Coulomb or donor–acceptor interactions depending on the functional composition of the nanodiamond surface. In the case of nanodiamonds with carboxyl groups on their surface, the complexes were formed through the Coulomb interactions, while the donor–acceptor mechanism was realized in the presence of nitrate ions on the surface.

Does Biosynthetic Silver Nanoparticles Are More Stable With Lower Toxicity than Their Synthetic Counterparts?

Control of size and shape is a challenge in nanoparticle synthesis. Synthetic and biosynthetic (both extracellular and intracellular) methods are used to prepare silver nanoparticle (SNP). In this study, the behavior of three strains of Staphylococcus aureus (S. aureus) was investigated in the presence of silver nitrate intra- and extracellularly. S. aureus strains biosynthesized SNPs intracellularly, while in the method of the extracellular biosynthesis, none of the strains could produce the SNP under different conditions (dark, bright light, and the presence of nitrate ion). Intracellular SNPs were purified. The results of this study and previous results were used to compare different properties of the biosynthetic (intra- and extracellular) and synthetic SNPs in terms of shape, size, zeta potential, stability, and toxicity. The results confirmed lower toxicity of biosynthetic SNPs in-vitro assays, and their more stability with less aggregation compared to the synthetic ones. Also, the biosynthetic nanoparticles were found uniform and small. These nanoparticles may be useful for being employed as biosensors.

Nitrate ion effect on gold nanorods plasmon resonance behavior: A potential chemical sensor

High sensitivity of surface plasmon resonances (SPR) in noble metals to the surrounding refractive index variations in the environment is a powerful bio-sensing technique. Here, we report the development of a simple colorimetric detection method for nitrate ion in water using gold nanorods (Au-NRs). Au-NRs suspension with the average aspect ratio of 3.5 was prepared by a modified seed growth method. According to the safety limit standard of nitrate amount in drinking water, different volumes of 10 mg/l nitrate solution were added to the Au-NRs suspension. Adding the nitrate group to the suspension resulted in turning to the nanorods with lower aspect ratios and finally spherical nanoparticles. The concentration of nitrate in water can be determined by monitoring with the naked eye and a UV–Vis spectrometer. It was shown that lower volumes of nitrate additive (25 μl) was a better identifier than those with higher volumes (50–150 μl). The color of Au-NRs suspension turned somehow from faint pink to purple after two days of adding 25 μl of nitrate solution. In addition, the UV–Vis absorption peak corresponding to longitudinal SPR (LSPR) blue-shifted from 814 nm to 712 nm after two days while the peak corresponding to transverse SPR (TSPR) showed a slight shift from 519 nm to 521 nm. Much more effect of nitrate group on LSPR than TSPR showed that nanorods are better identifier and biosensors than spherical nanoparticles. Decomposing and converting the Au NRs to sphere particles and lowering the initial aspect ratio of NDs in presence of nitrate ion is reported for the first time, but more works needed for talking about its mechanism.