In this research, a novel, simple, biodegradable and nontoxic sensor based on preparation of polyvinyl alcohol-borax hydrogel functionalized with gold nanoparticles (PBH@AuNPs) are introduced for ceftriaxone determination. The in situ synthesis of AuNPs into PBH is performed without adding any reducing agent in the hydrogel matrix. The absorption peak of sensor was deceased in the presence of specified ceftriaxone concentration due to electrostatic interactions between the AuNPs embedded into the PBH substrate and nitrogen-sulfur functional groups of the ceftriaxone structure. The decrease in the absorbance peak is used as an analytical signal for ceftriaxone determination. AuNPs morphology, PBH and PBH@AuNPs characteristics were investigated. The influence of chemical variables such as pH, volume and concentration of buffer, concentration of gel maker agents, temperature and exposure time of PBH in hot water was also investigated. Under the established optimum conditions, the calibration graph was linear in the range of 1.0-90.0 µg mL-1 with a limit of detection 0.327 µg mL-1. The relative standard deviation for 20.0 and 70.0 µg mL-1 of ceftriaxone was 4.02 and 2.19 % (ten replicate measurements), respectively. This sensor exhibited a promising potential for rapid, simple and real-time detection of ceftriaxone in biological samples such as human plasma and urine samples with acceptable results.

A novel dual mode “on and off” fluorescence probe was developed based on silver dots loading into polyvinyl alcohol and borax hydrogel (AgD-PBH) for Fe (III) and thiosulfate determination for the first time. The label free silver dots were in situ synthesized and embedded into PBH matrix without adding any reducing agent. PBH acts as a template for AgD stabilization and as a reducing agent for in situ synthesis of them. The characteristics of this probe were investigated using XRD microanalysis, TEM, EDX and UV-Visible spectrophotometry. It was also observed that the size of AgD was decreased and the fluorescence intensity was enhanced in the presence of Fe (III). In this state, the florescence probe is in the on position. After subsequent addition of thiosulfate which shows an increase in the size of particles, the fluorescence intensity was quenched. It is off mode. The change in the fluorescence intensity was recorded as an analytical signal for Fe (III) and thiosulfate determination. The effect of different parameters such as pH, silver nitrate concentration, borax concentration, PVA concentration and time response of the probe was investigated. Under the approved condition, the linear range was validated over the concentration of 0.14-26.86 µM and 0.1-1.0 µM for Fe (III) and thiosulfate, respectively. The limit of detections is 4.5× 10-2 µM and 0.06 µM for Fe (III) and thiosulfate, respectively. The relative standard deviation for 2.69 and 17.91 µM of Fe (III) was 3.18 and 1.07 % (ten replicate measurements), and for 0.4 and 0.8 µM of thiosulfate was 7.73 and 4.25 %, respectively. The proposed method was successfully applied to Fe (III) detection in different food samples.

The aim of recent research was to developed a new turn-on fluorescence bio-probe for insulin monitoring based on in situ synthesis and embedding of Ag dots into biodegradable polyvinyl alcohol and borax hydrogel (PBH@AgD). The characteristics and morphology of bio-probe were investigated using XRD, TEM, DLS and EDX. According to metal enhanced fluorescence (MEF) mechanism, interaction of fluorophores of insulin protein through its sulfur or nitrogen with Ag dots and also the orientation of fluorophores could be responsible for the enhanced emission peak at 300 nm by increasing the insulin concentration. The enhanced fluorescence which is proportional to the increase of insulin concentration has been used as an analytical signal for insulin detection. The parameters affecting the bio-probe were optimized to enhance the selectivity and sensitivity of the method by investigating the effect of variables. Under optimum conditions, the enhanced fluorescence intensity of insulin concentration was linearly proportional to the insulin concentration in the range of 5–220 ng mL−1. The limit of detection is 0.1 ng mL−1. The relative standard deviation of was 0.42 and 0.13% (n = 10) for two concentrations of 60 and 140 ng mL−1, respectively. The proposed system was successfully applied to insulin assay in human blood serums and regular insulin samples.

In this study, a facile and one-pot method was developed for mercury and chemet drug detection based on off-on fluorescence of carbon quantum dots (CQDs). The synthesis protocol of CQDs was easily performed with a rapid and simple hydrothermal method, in which Prosopis Juliflora leaves were used as a green and low cost source for the designed fluorescent probe. This prepared CQDs exhibited a blue luminescence with a 5% quantum yield. The off fluorescence is observed in the presence of different concentrations of mercury (II) which is specifically recovered with the addition of chemet as a succimer drug. The paramagnetic ions such as Hg (II) could be coordinated by functional groups of the surface and the edge of CQDs like NH, SH and COO. Therefore it causes the fluorescence quenching. The addition of different concentrations of chemet, the surface of carbon dots gets free of Hg (II) ion. The Hg (II) ions have a particular binding preference to chemet because of its specific steric structure and very good coordination sites. As a consequence the realising process can easily happen for Hg (II) attached to CQDs due to decomposing of CQDs-link-Hg. Hence, the fluorescence intensity of CQDs is recovered to the “on” state in the presence of chemet. The characteristics and morphology of CQDs were investigated using UV-Vis spectroscopy, TEM, DLS, XRD and FT-IR. Important parameters such as pH, photo stability and reaction time were also investigated. Under the optimal condition, two linear calibration were validated over the range of 5-500 ng mL-1 (LOD= 1.3 ng mL-1) and 2.5-22.5 ng mL-1 (LOD= 1.4 ng mL-1) for Hg (II) and chemet, respectively. The relative standard deviation for 50 and 500 ng mL-1 of Hg (III) was 4.46 and 1.66 % (ten replicate measurements), and for 10 and 20 ng mL-1 of chemet was 3.89 and 1.29 %, respectively. This methodology was successfully applied to measurements of Hg (II) in the water samples.

In this research, a novel resonance Rayleigh scattering (RRS) aptasensor has been synthesized for thrombin monitoring using in-situ synthesized and embedded Au nanoparticles (AuNPs) into poly vinyl alcohol–borax hydrogel (PBH). Thiolated- thrombin binding aptamer (thiolated-TBA) was attached to the surface of AuNPs embedded into PBH. To further verification of synthesis steps, the characteristics and morphology of PBH and AuNPs-PBH were investigated using EDX, TEM, DLS and UV-Vis spectra. In this method, an increase in the RRS intensity of the novel PBH-aptasensor (thiolated-TBA@AuNPs–PBH) at scattering wavelength of 500 nm which is proportional to the increase of thrombin concentration was selected as an analytical monitoring signal for thrombin detection. The enhancement of RRS intensity indicates that the designed probe was reacted with thrombin target, a structural alteration was happened for aptamer and TBA folds into a chair form anti-parallel G-quadruplex. The parameters affecting the PBH-aptasensor such as pH, buffer, ionic strength, salt concentration and etc. were optimized to enhance the selectivity and sensitivity of the method. Under the approved conditions, the proposed aptasensor showed a good linear relationship between ∆IRRS and lgthrombin concentration over the concentration range of 0.70 pM- 0.02 µM. The detection limit of the proposed method was obtained 0.10 pM. The relative standard deviations were 4.03 and 2.66 % (n=10) for two thrombin concentrations of 5.6 pM and 3.6 nM, respectively. This method was applied for thrombin detection in serum samples of healthy volunteers with acceptable result. This oligonucleotide-based sensing system is capable of sensitive and specific detection of thrombin protein with trace amount of PBH-aptasensor and RRS technique. This method can be widely applied for proteins detection in clinical laboratories.

In this research, a novel fluorescence sensor has been developed based on imprinted sol gel functionalized with CdS quantum dot capped with thio-glycolic acid (CdS@TGA) for creatinine determination. CdS quantum dot was synthesized with capping agent of thio-glycolic acid and covalently bonded to sol gel monomers through a bio-conjugation reaction, resulting the formation of a carbodiimide bond and binding of the carboxyl-functional of TGA to the amine-terminated of 3-Aminopropyl) triethoxysilane (APTES). The sol gel matrix is formed based on silica .Creatinine acts as a template for making of specific binding sites in a sol gel bed. The designed sensor has been used to measure creatinine by fluorimetric method and the change in fluorescence intensity of quantum dots has been monitored as a response signal. The effect of important parameters such as pH, type and volume of buffer, volume of functional monomer, volume of crosslinker, volume of CdS@TGA, volume of NHS and EDC, reaction time were investigated and optimized to enhance the sensitivity of creatinine determination. The present method is capable of determining creatinine by plotting the response ratio (F0/F) as a function of the concentration of creatinine. Calibration curves for imprinted and non-imprinted probes were linear in the concentration range of 2- 10 μg mL-1 0.5 -12 μg mL-1, respectively. The limit of detection was 0.08 μg mL-1 for imprinted probe. The relative standard deviation for 1 μg mL-1 and 10 μg mL-1 was 4.53 and 2.13 % (ten replicate measurements), respectively. Our proposed probe has been successfully applied for creatinine detection in the human serum and children’s urine samples.

In this research, the synthesis method of label free CuNPs and CuNPs with different coatings have been developed based on PBH bed. The characterization and morphology of CuNPs, CuNPs with capping agent of thiourea embedded into PBH (CuNPs@TU-PBH) and CuNPs with capping agent of L-glutathione embedded into PBH (CuNPs@L-Glu-PBH) were investigated using TEM, DLS and UV-Visible spectrophotometry. The proposed method is simple, inexpensive and biocompatible. Also, the different type of CuNPs can be synthesized using this method with high stability in water phase.
 

In this research, a novel adsorbent, Silicon Carbide nanoparticle coated on 1-Butyl3-mthyl Imidazulium hexa flouro phosphate (SiC-NP-ILs) was synthesized by a simple, low cost and efficient procedure for the removal of Nuclear Fast Red (NFR) from aqueous solutions. Subsequently, this novel material characterization and identification has been completed by different techniques such as TEM, FT-IR and UV-Vis spectrometry analysis. In batch experimental set-up, optimum conditions for quantitative removal of NFR by SiC-NP-ILs was attained following searching effect of variables such as adsorbent dosage (50-350 mg), contact time (10-120 min), solution pH (6-10), and initial concentration of dye (10–60 mg L-1) on the adsorption process was investigated. Optimum values was set as pH of 8.0, 250 mg of SiC-NP-ILs at removal time of 40 min. Kinetic studies at various adsorbent dosage and initial NFR concentration show that maximum dye was sequestered within 10 min of the start of every experiment at most conditions. The adsorption of NFR follow the pseudo-second-order rate equation in addition to interparticle diffusion model (with removal more than 99%) at all conditions. Equilibrium data fitted well with the Langmuir model at all amount of adsorbent, while maximum adsorption capacity was 14.22 mg/g for 0.2 g of SiC-NP-ILs. The present procedure is green and offers advantages such as shorter reaction time, simple workup, and high percentage removal.
A new approach is presented in this paper by using dispersed SiO2 nanoparticles (SiO2-NPs) in a combined cloud point and solid phase extraction for the efficient preconcentration and determination of Zn2+ and Fe2+ in various samples.In this method Zn2+ and Fe2+ ions are adsorbedon SiO2-NPs and transferred in to surfactant rich phase.Subsequently the Zn2+ and Fe2+ ions are desorbed from SiO2-NPs by a Nitric acid solution.The influence of chemical variables such as pH of the sample solution, electrolyte ,amount of SiO2-NPs, type and volume of the eluent on the extraction system was studied. The calibration graph was linear in the range of 5.0–120.0 ng mL-1 of Zn2+&Fe2+ (r=0.9965&r=0.9979) was achieved and the limit of detection for Zn2+ and Fe2+ was 0.051 and 0.041 ng mL-1. The relative standard deviation (RSD) for eight replicate measurements of 100 ng mL-1 Zn2+and Fe2+ was 1.96%and1.12% respectively. The proposed method was successfully applied to the quantitative determination of Zn2+ and Fe2+ in tapwater,and food samples.
A sensitive, simple and novel method was developed to determine 2-mercaptobenzothiazole (2MBT) in water samples. This method was based on the interaction between gold nanoparticles (AuNPs) and 2MBT followed by increasing of the resonance Rayleigh scattering (RRS) intensity of nanoparticles. The change in RRS intensity (DIRRS) was linearly correlated to the concentration of 2MBT over the ranges of 5.0–100.0 and 100.0–300.0µg L-1. 2MBT can be measured in a short time (5 min) without any complicated or time-consuming sample pretreatment process. Parameters that affect the RRS intensities such as pH, concentration of AuNPs, standing time, electrolyte concentration, and coexisting substances were systematically investigated and optimized. Interference tests showed that the developed method has a very good selectivity and could be used conveniently for determination of 2MBT. The limit of detection (LOD) and limit of quantification (LOQ) were 1.0 and 3.0 l g L-1, respectively. Relative standard deviations (RSD) for 20.0 and 80.0 l g L-1 of 2MBT were 1.1 and 2.3, respectively. Possible mechanisms for the RRS changes of AuNPs in the presence of 2MBT were discussed and the method was successfully applied for the analysis of real water samples.

- A sensitive, simple and novel method was developed to determine thiram fungicide in water and plant samples. This method was based on the interaction between gold nanoparticles(AuNPs) and thiram fungicide followed by increasing of the Resonance Rayleigh scattering(RRS) intensity of nanoparticles. The change in RRS intensity (ΔIRRS) was linearly correlated to the concentration of thiram over the range of 1.0–200.0 mg L-1. Thiram can be measured in a short time(4min) without any complicated or time consuming sample pretreatment process. Parameters that affect the RRS intensities such as pH, concentration of AuNPs, standingtime, electrolyte concentration,and coexisting substances were system- atically investigated and optimized. Interference tests showed that the developed method has a very good selectivity and could be used conveniently for the determination of thiram.The limit of detection (LOD) and limit of quantification (LOQ) were 0.3 and 1.0 mg L_1, respectively. Relative standard deviations (RSD) for 20.0 and 80.0 mg L-1 of thiram were 3.0 and 1.1, respectively. Possible mechanisms for the RRS changes of AuNPs in the presence of thiram were discussed and the method was successfully applied for the analysis of spiked real water samples and fresh plant samples such as tomato and cucumber.

 This study describes a method based on both SPR and cloud point extraction of silver nanoparticles (AgNPs) for the determination of Cu2+. Label free AgNPs are enriched into a non-ionic surfactant phase and show strong SPR intensity. Copper (II) suppresses the transfer of AgNPs into the surfactant and decreases the SPR intensity. The decrease in the absorbance of the surfactant rich phase in the presence of Cu2+ is used as an analytical signal for the determination of copper. The influence of chemical variables such as pH of the sample solution, ionic strength, and concentration of the AgNPs on the cloud point extraction was investigated. Under the optimum conditions, the extent of the decrease in SPR absorption intensity was linearly proportional to the concentration of Cu2+ in the range of 0.5–60.0 ng mL-1 with a detection limit of 0.4 ng mL-1. The relative standard deviations of ten replicate measurements of 10 ng mL-1 and 40 ng mL-1 of Cu2+ were 4.15% and 3.71% respectively. The proposed method was successfully applied in the determination of Cu2+ in food samples with satisfactory results.
In this work, green curcumin nanoparticles (CURNs) are introduced for colorimetric sensing of sulfide using micelle mediated cloud point extraction for the first time. CURNs are transferred into non-ionic surfactant phase and show strong absorption intensity. The extraction of CURNs to the surfactant rich phase is suppressed in the presence of Cu2+ but upon addition of sulfide, the extraction of CURNs to the surfactant rich phase is increased again. This increase in the absorbance of surfactant rich phase is related to the sulfide concentration and was used as an analytical signal for the sensing of sulfide. The effect of chemical variables such as pH of the sample solution, concentration of Cu2+, electrolyte and CURNs on the cloud point extraction was studied. Under optimum conditions, the change in absorption intensity was linearly proportional to the concentration of sulfide in the range of 2–200 ng mL-1 with a detection limit of 1.4 ng mL-1. The relative standard deviations for 10 replicate measurements of 20 ng mL-1 and 175 ng mL-1 of sulfide were 4.08% and 1.44% respectively. The method was successfully applied to the determination of sulfide in different water samples.
This study presents a simple and efficient measurement system for quantitative sensing of blood hemoglobin (Hgb) using curcumin nanoparticles (CURNs). The Hgb monitoring is based on CURNs aggregation in the presence of Hgb, which leads to a decrease in the absorption intensity of CURNs. In this study the analytical signal for the measurement of blood Hgb concentration was defined as the difference in absorption intensity of the CURNs in the absence and presence of Hgb. The method was optimized to enhance the selectivity and sensitivity of the method by investigating the effect of variables such as pH of the sample solution, buffer concentration, required amount of CURNs, equilibrium time and tolerance limit of various probable interferences. Under optimum conditions, the difference in absorption intensity of the CURNs was linearly proportional to the concentration of Hgb in two ranges 1–40 µg mL-1 and 150–1200 µg mL-1 with a detection limit of 0.1 µg mL-1. The relative standard deviation (RSD) for ten replicate measurements of 20 µg mL-1 and 600 µg mL-1 of Hgb was 3.60% and 3.13% respectively. The sensing method was successfully applied for the measurement of Hgb in human blood with satisfactory results.
This work describes the design and fabrication of a novel lab-on-paper device for pH sensing using curcumin nanoparticles (CURNs). In order to fabricate the lab-on-paper, the wax dipping method was used. The color of loaded paper with CURNs changed from yellow to orange and red to brown in the pH range of 7–13. The image of the lab-on-paper was taken by a digital camera and the picture was processed and analyzed using Adobe Photo shop software. The change in mean color intensity with pH was recorded and employed as an analytical signal for quantitative sensing of pH. The parameters affecting the pH sensor were optimized to enhance the selectivity and sensitivity of the method. Under optimum conditions, the mean color intensity was linearly proportional to the pH in the range of 8–13. The relative standard deviations of 10 replicate measurements of pH=9 and pH=12 were 2.79% and 1.02%, respectively. The developed sensor was successfully applied to the determination of pH in different water samples with satisfactory results.
The aim of recent research was to employ curcumin nanoparticle (CURN) in paper based analytical devices for monitoring of Hg2+. The measurable visual ability of CURN for sensing of Hg2+ was first examined in visible area by UV-Visible spectrophotometer. Here, the analytical signal was defined as the mean color intensity of each test zone that it increases following the increase the Hg2+ concentration. In this work, wax dipping technique was utilized to create the paper based probe. Some important parameters such as pH, buffer, ionic strength and multiple additions of CURN and analyte have been investigated in detail. The calibration graph was linear in the range of 0.5-20 μg mL-1 Hg2+ with the limit of detection 0.17 μg mL-1 (without preconcentration) and 0.01 µg mL-1 Hg2+ (after 50 times preconcentration). The relative standard deviation of ten replicate measurements for 2 µg mL-1 and 10 µg mL-1 of Hg2+ were 4.47% and 2.89%, respectively. This assay proffers great promise as a simple, portable, cost-effective, user and environmental friendly probe for high selective recognition of Hg2+.
We report herein the development of a simple fluorometric method for monitoring of 2-mercaptobenzothiazole (MBT) by using CdTe quantum dots (CdTe-QDs) in paper based analytical devices (PADs). The wax dipping technique was applied to create the PADs. The ability of CdTe-QDs for fluorometric sensing of MBT was first examined in the solution media by spectrofluorophotometer. The color (fluorescence) of loaded paper with CdTe-QDs under UV radiation faded away up on addition of MBT due to its fluorescence quenching. The image of the PADs was taken by a digital camera and the picture was processed and analyzed using Adobe Photo shop software. Here, the increase in the mean color intensity of the PADs test zones up on addition of MBT was served as analytical signal for monitoring of MBT. The parameters affecting the paper MBT probe were optimized to enhance the selectivity and sensitivity of the method. Under optimum conditions, the mean color intensity was linearly proportional to the concentration of MBT in the range of 1–50 µg mL-1 with a detection limit of 0.5 µg mL-1. The relative standard deviation of ten replicate measurements of 20 µg mL-1 of MBT was 1.27%. The proposed sensor was successfully applied to the determination of MBT in different water samples with satisfactory results.
Herein, we introduce a new strategy that allows for green, in-situ generation of silver nanoparticles using flexible and transparent bacterial cellulose nanopapers. In this method, adsorbed silver ions on bacterial cellulose nanopaper were reduced by the hydroxyl groups of cellulose nanofibers, acting as the reducing agent. This process results in the fabrication of bionanocomposite “Embedded silver nanoparticles in transparent nanopaper” (ESNPs) without any need for the addition of external linking, stabilizing or reducing agents. The fabricated ESNPs were investigated and characterized by field emission scanning electron microscopy (FE-SEM), UV–Visible spectroscopy (UV–Vis), thermogravimetric analysis (TGA) and energy-dispersive X-ray spectroscopy (EDX). The important parameters affecting the ESNPs were optimized during the fabrication of specimens. The resulting ESNPs were used as a novel and sensitive probe for the optical sensing of cyanide ion (CN-) in water samples with satisfactory results. The change in surface plasmon resonance absorption intensity of ESNPs was linearly proportional to the CN- concentration in the range of 0.2 – 2.5 µg mL-1 with a detection limit of 0.012 µg mL-1.

 Silicon carbide nanoparticles were applied as a new solid phase adsorbent for preconcentration of lead ions. Pb(II) ions are adsorbed on silicon carbide nanoparticles, eluted with nitric acid and determined by flame atomic absorption spectrometry. The solid phase extraction conditions were optimized. The calibration graph was linear in the range of 2–150 ng mL-1 (r = 0.9995) with a detection limit of 0.4 ng mL-1. The relative standard deviation for eight measurements of 20 ng mL-1 of Pb(II) was 1.3%. The adsorption capacity was 156.2 mg g-1of Pb(II). The method was applied to determination of Pb(II) in different samples.

-This article presents a simple, green and low cost analytical method for preconcentration and determination of β-carotene nanoparticles content in food and juice samples. The method is based on the enrichment of β-carotene nanoparticles in non-ionic surfactant phase using cloud point extraction (CPE) followed by UV-vis spectrophotometric determination at 468 nm. The influence of chemical variables such as pH of the sample solution, type and volume of the buffer, electrolyte type and concentration, surfactant concentration, temperature and incubation time on CPE procedure was studied. Under the optimum conditions the method yielded a linear calibration curve in the range of 0.03-3.00 mg L-1 for β-carotene nanoparticles (r=0.9978). The relative standard deviation (RSD) of 3.2% and 5.6% for eight replicate measurements of 2.00 mg L−1 and 0.33 mg L−1 of β-carotene nanoparticles was obtained. The developed CPE method was applied for analysis potato, watermelon, tomato fruits and cherry and orange juices samples. The recoveries for the analyte in spiked samples were in the range of 93-104%.

- A new approach is presented in this paper by using dispersed TiO2 nanoparticles (TiO2-NPs) in a combined cloud point and solid phase extraction for the efficient preconcentration and determination of Zn2+ in various samples. In this method Zn2+ ions are adsorbed on TiO2-NPs and transferred into surfactant rich phase. Subsequently the Zn2þ ions are desorbed from TiO2-NPs by a dithizone solution via forming a color complex which could be detected colorimetrically. The influence of chemical variables such as pH of the sample solution, electrolyte, amount of TiO2-NPs, type and volume of the eluent on the extraction system was studied. The calibration graph was linear in the range of 0.5– 90.0 mg L-1 of Zn2+ (r = 0.9996). An enrichment factor of 80 was achieved and the limit of detection for Zn2+ was 0.33 mg L-1. The relative standard deviation (RSD) for eight replicate measurements of 10 mg L-1 and 60 mg L-1 of Zn2+ was 1.8% and 1.5% respectively. The proposed method was successfully applied to the quantitative determination of Zn2+ in tap water, powder milk and Zinc sulfate tablet with satisfactory results.

- Herein, d-limonene and β-carotene as two natural compounds are introduced in dispersive liquid-liquid microextraction (DLLME) method for spectrophotometric determination of β-cyclodextrin (β-CD). Dissolved β-carotene in d-limonene that is used as a green solvent lighter than water in DLLME method exhibits strong absorption intensity. The absorption intensity of extraction solvent phase is increased in the presence of β-CD due to its interaction (complex formation) with β-carotene. This increase in the absorbance of extraction solvent phase is related to the β-CD concentration and was utilized as analytical signal for determination of β-CD. The effect of chemical variables such as pH of sample solution, nature and volume of disperser solvent, volume of extraction solvent and extraction time on the DLLME method was studied and optimum conditions were established. The calibration curve is linear in the range of 0.1-6 mmol L-1 (r = 0.9956) with a limit of detection 0.04 mmol L-1. The relative standard deviation for 8 replicate determinations of 1×10-4 mol L-1 and 5×10-3 mol L-1 of β-CD were 1.82 % and 0.88 % respectively. The proposed method was successfully utilized to determine β-CD in spiked water and pharmaceutical samples and good spiked recoveries were obtained in the range of 94.2-108.0 %.

- There is a rapid growth in commercial produce and application of silver nanoparticles (AgNPs) (e.g., in cosmetics products, food technology, textiles and fabrics, and medical products and devices) that will inevitably increase exposure to silver in the environment and among the general population. Compared to the vast application of silver, information on the fate, the transformation and the toxic effects of AgNPs is very limited. Thus, to protect consumer health and the environment, development of methods for analysis of AgNPs is an urgent need to achieve detailed insights into the fate, the transport and exposure of AgNPs in environment. In this study, a new, simple and reliable method for the quantification of silver nanoparticles (Ag-NPs) in environmental samples in the nanogram per liter range by chitin nanofiber. In present method Silver nanoparticles is absorbed and enriched in chitin nanofiber. Then, a picture is captured by a digital camera; its color intensity is measured by image j software. The experimental conditions were studied for this method. Under the established optimum conditions, the calibration graph was linear in the range of 1.6–40 nmol mL-1 of nanosilver with a limit of detection of 1.31 nmol mL-1 .The relative standard deviations for eight replicate determinations of 9 and 24 nmol mL-1 of nanosilver were 1.5% and 0.5%, respectively. Samples of different complexity such as river water, treated and untreated municipal waste water were spiked with different concentrations of Ag-NPs and a high recovery was found in all cases.

- Herein, we introduce a new strategy that allows for green, in-situ generation of silver nanoparticles using flexible and transparent bacterial cellulose nanopapers. In this method, adsorbed silver ions on bacterial cellulose nanopaper were reduced by the hydroxyl groups of cellulose nanofibers, acting as the reducing agent. This process results in the fabrication of bionanocomposite “Embedded silver nanoparticles in transparent nanopaper” (ESNPs) without any need for the addition of external linking, stabilizing or reducing agents. The fabricated ESNPs were investigated and characterized by field emission scanning electron microscopy (FE-SEM), UV–visible spectroscopy (UV–vis), fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and energy-dispersive X-ray spectroscopy (EDX). The important parameters affecting the ESNPs were optimized during the fabrication of specimens. The resulting ESNPs were used as a novel and sensitive probe for the optical sensing of 2-mercaptobenzothiazole (MBT) in water samples with satisfactory results. The change in surface plasmon resonance absorption intensity of ESNPs was linearly proportional to the concentration in the range of 2 – 110 µg mL-1 with a detection limit of 1.37 µg mL-1 for MBT.

-In this work, nano Lawson as a natural compounds are introduced in dispersive liquid-liquid microextraction (DLLME) method for spectrophotometric determination of Cholesterol. The experimental conditions were studied for the DLLME method. The effect of chemical variables such as pH of sample solution, nature and volume of disperser solvent, nature and volume of extraction solvent and extraction time on the DLLME method was studied and optimum conditions were established. The calibration curve is linear in the range of 5-200 mg L-1 (r > 0.998) with a limit of detection 4.1 mmol L-1. The relative standard deviation for 8 replicate determinations of 25 mg L-1 and 150 mg L-1 of cholesterol were 3.96 % and 1.52 % respectively. The proposed method was successfully utilized to determine cholesterol in serum blood, egg and yoghurt.

 A new sensitive indirect micelle-mediated cloud point extraction method has been developed for determination of trace amounts of nitrite by spectrophotometry. The method is based on the well known oxidation–reduction reaction of nitrite by iodide ion in acidic medium and cloud point extraction of I3− formed from aqueous solution using Triton X-100. The rich extracted surfactant phase is diluted with water and its absorbance is measured at 365 nm. The effects of different operating parameters such as pH, standing time, concentrations of acid, potassium iodide and surfactant, temperature, incubation time and the possibility of interferences of the various species on the determination of nitrite were studied in details. A linear calibration graph was obtained in the range of 8–120 ng mL−1. The limit of detection (LOD) based on three times the standard deviation of the blank (3Sb) was 6.0 ng mL−1(n=10). The method is applied for measurement of nitrite in meat products such as sausages and water samples. There is good agreement between the mean values of the Griess standard and the proposed method.

A new indirect cloud point extraction method has been developed for determination of trace amounts of penicillin G by spectrophotometry. The method is based on the effect of penicillin G on the cloud point extraction of triiodide ion. Penicillin G is converted to the corresponding penicilloic acid by carrying out the hydrolysis in basic medium, and it yields D-penicill amine upon treatment with acid whose product is oxidized quantitatively by iodine to give rise to disulphide. The remaining triiodide ion is extracted into surfactant solution containing Triton X-100 and the difference between absorbance of working solution in the presence and absence of penicillin G is proportional to the amount of penicillin G. The effect of various operating parameters, such as concentrations of sodium hydroxide, hydrochloric acid, surfactant and I3-, temperature, incubation time and the possibility of interferences of the various species on the cloud point extraction have been studied. A linear calibration graph was obtained in the range of 50-1250 ng mL -1. The limit of detection was 38 ng mL -1 (n=10). The method successfully was applied to determination of penicillin G in milk samples.

In another study, synthesis of nanocomposite chitosan-alumina and its application as a solid phase for simultaneous measurement of Cu2+ and Cd2+ was investigated. In this work, firstly, chitosan was extracted from shrimp shell. Then by absorption method chitosan was settled on the surface of alumina. Finally in the presence of Triton X-100 and by the use of polysulphid, a nanoparticles of chitosan-alumina was synthesized. In continuation the synthesized nanoparticles in above was used as a sorbent for simultaneous measurement of Cu2+and Cd2+ ions. Different parameters affecting adsorption of cations by on adsorbent, such as pH, type and concentration of buffer, type and concentration of eluent, solution flow rate, mass of adsorbent, solution volume and the possibility of interferences of the various ions were investigated. A linear calibration graph was obtained in the range of 2-150 and 1.25–40 ngmL−1 for Cu2+ and Cd2+ respectively. The limit of detection (LOD) based on three times the standard deviation of the blank (3Sb) was 0.7 and 0.5 ng mL−1 (n=10) for Cu2+ and Cd2+, respectively. A preconcentration factor of 67 was obtained in this method. The proposed method was successfully applied for measurement of Cu2+ and Cd2+ in tap and river water samples.

In the next work, a new grafted nano-composite of alumina-chitosan was synthesized. In order to synthesize this grafted nano-composite, at first, nano-composite chitosan-alumina synthesized in the previous work was added to chloroacetic acid solution and then, for protonation of new nano-composite, it was placed in concentrated hydrochloric acid at room temperature. The synthesized nano-composite, as an adsorbent, was tested for removal of fluoride ion from aqueous solutions. The concentration of fluoride after removal was determined using its effect on ferric thiocyanate complex and measuring the absorbance at maximum wavelength of complex (λmax=449.5) by spectrophotometer. The effect of different parameters such as pH, type and concentration buffer, stirring time on magnetic stirrer, mass of adsorbent, volume of solution and effect of different anions were studied. The proposed procedure was applied to the removal of fluoride in tap and river water samples and good recoveries were obtained. The data were fitted to Langmuir and Freundlich isotherms and the results showed a better fitting to the Langmuir isotherm. The maximum adsorption capacity was found to be 29.4 mg g-1 for fluoride. The kinetic studies indicate that the adsorption follows the pseudo-second order kinetics.

The synthesized nano-composite of chitosan-alumina-acetic acid, as an adsorbent, was tested for the removal of indigo carmine dye from aqueous solutions. 0.15 g of protonated grafted nano-composite was suspended in 50 mL solution containing 100 mg L-1 indigo carmine dye and stirred. The concentration of indigo carmine dye after removal was determined using its calibration curve and measuring the absorbance at maximum wavelength of dye (λmax=620) by spectrophotometer. The effect of different operating parameters such as pH, concentration acid, stirring time on magnetic stirrer, mass of adsorbent, volume of solution and effect of different cationic and anionic species were studied. The method was applied to the removal of indigo carmine from different water samples and good recoveries were achieved. The kinetic studies indicated that the adsorption followed the pseudo-second order kinetics. The Langmuir isotherm model provided the best correlation of the experimental data. The maximum adsorption capacity was found to be 83.3 mg g-1 for indigo carmine.