Neutral Phosphate Buffer Solution Research Articles

CeO2·ZnO@biomass-derived carbon nanocomposite-based electrochemical sensor for efficient detection of ascorbic acid

Ascorbic acid (AA), a prominent antioxidant commonly found in human blood serum, serves as a biomarker for assessing oxidative stress levels. Therefore, precise detection of AA is crucial for swiftly diagnosing conditions arising from abnormal AA levels. Consequently, the primary aim of this research is to develop a sensitive and selective electrochemical sensor for accurate AA determination. To accomplish this aim, we used a novel nanocomposite comprised of CeO2-doped ZnO adorned on biomass-derived carbon (CeO2·ZnO@BC) as the active nanomaterial, effectively fabricating a glassy carbon electrode (GCE). Various analytical techniques were employed to scrutinize the structure and morphology features of the CeO2·ZnO@BC nanocomposite, ensuring its suitability as the sensing nanomaterial. This innovative sensor is capable of quantifying a wide range of AA concentrations, spanning from 0.5 to 1925 μM in a neutral phosphate buffer solution. It exhibits a remarkable sensitivity of 0.2267 μA μM−1cm−2 and a practical detection limit of 0.022 μM. Thanks to its exceptional sensitivity and selectivity, this sensor enables highly accurate determination of AA concentrations in real samples. Moreover, its superior reproducibility, repeatability, and stability underscore its reliability and robustness for AA quantification.

Electrochemical detection of hydroquinone as an environmental contaminant using Ga2O3 incorporated ZnO nanomaterial

The primary objective of this research endeavor is to develop a highly sensitive and selective electrochemical sensor for the accurate detection of hydroquinone (HQ), a prevalent environmental contaminant. To achieve this, we employed a novel nanocomposite consisting of Ga2O3-doped ZnO (Ga2O3.ZnO) as the active nanomaterial for fabricating a glassy carbon electrode (GCE). The structure and morphology of the Ga2O3.ZnO nanocomposite were rigorously analyzed using a diverse range of techniques to ensure its suitability as the sensing nanomaterial. This innovative sensor exhibits remarkable capabilities, enabling the detection of HQ across a broad concentration range, spanning from 1 to 11070 µM, in a neutral phosphate buffer solution. It boasts an exceptionally high sensitivity of 1.0229 µA µM−1 cm−2 and an impressive detection limit of 0.063 µM. Thanks to its exceptional sensitivity and specificity, this sensor can precisely quantify HQ levels in real-world samples. Moreover, its outstanding reproducibility, repeatability, and stability establish it as a dependable and resilient choice for HQ determination.

Facile synthesis of CeO2·CuO-decorated biomass-derived carbon nanocomposite for sensitive detection of catechol by electrochemical technique

Catechol (CC) is renowned for its ability to interact with a wide range of biomolecules, a trait that raises potential health concerns. Consequently, herein we achieved a significant milestone by developing an electrochemical CC sensor with improved performance such as exceptional sensitivity and selectivity. In this CC sensor we used Cerium (IV) oxide-doped Copper (II) oxide decorated biomass-derived carbon (BC) nanocomposite, known as CeO2·CuO@BC as the sensing material. This material has been artfully integrated into the modification of a glassy carbon electrode (GCE), showcasing the synergy of advanced materials and electrode design. The efficacy of the CeO2·CuO@BC nanocomposite as a sensing material underwent rigorous evaluation through comprehensive characterization techniques such as X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectrum, Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), and Energy-Dispersive X-ray Spectroscopy (EDS). As a result, we developed a sensor that can quantify CC concentrations across an extensive dynamic range, spanning from 0.5 μM to a remarkable 8470 μM in a neutral phosphate buffer solution. This sensor, boasting a sensitivity of 0.4171 μAμM−1cm−2, coupled with an impressive detection limit of a mere 0.035 μM, stands as a testament to its superior performance. Its exceptional sensitivity and selectivity allow precise catechol level detection in real-world samples, making it invaluable for analytical applications. Beyond its analytical prowess, the sensor demonstrates remarkable durability through excellent reproducibility, repeatability, and stability. This robustness underscores its reliability, establishing it as an indispensable and highly efficient electrode for accurate CC determination across various practical scenarios.

Development of a sensitive and selective catechol amperometric sensor based on a novel In2O3-doped CuO decorated mesoporous carbon nanocomposite

Catechol is known for its reactivity with various biomolecules, posing potential health risks. Therefore, in this research, we have successfully developed an electrochemical sensor with high sensitivity and selectivity for detecting catechol (CC). The sensor utilizes a novel In2O3-doped CuO decorated Mesoporous Carbon Nanocomposite (In2O3.CuO@MC) as the sensing material, which is applied to fabricate a glassy carbon electrode (GCE). The suitability of the In2O3.CuO@MC nanocomposite as a sensing material was thoroughly examined using various characterization techniques. The developed sensor exhibited remarkable performance, enabling the accurate catechol determination across a wide concentration range, from 0.5 to 3031 µM, in a neutral phosphate buffer solution. This sensor demonstrated a high sensitivity of 0.3803 µAµM−1cm−2 and an impressive detection limit of 0.048 µM. The sensor's exceptional sensitivity and selectivity make it capable of precisely quantifying catechol from real samples. Its robustness is further highlighted by its excellent reproducibility, repeatability, and stability. As a result, this sensor proves to be a reliable and effective tool for precise catechol determination.

Oxygen reduction mediated by tetrapyridylalkylamine Cu(II) complexes with diimines

Oxygen reduction reaction (ORR) is important in artificial energy conversion systems such as fuel cells. However, it is kinetically sluggish. It is thereby highly desirable to develop ORR catalysts to improve the efficiency of energy conversion. In this work, three copper(II) complexes based on the hexadentate tetrapyridylalkylamine N,N,N’,N’-tetrakis(2-pyridyl-methyl)-1,4-butanediamine (tpbn), namely [Cu2(tpbn)(CH3OH)4(ClO4)2](ClO4)2 (Cu-tpbn), [Cu2(tpbn)(bpy)2](ClO4)4.2CH3COCH3 (Cu-tpbn-bpy, bpy = 2,2′-bipyridine), and [Cu2(tpbn)(Me2bpy)2](ClO4)4.3CH3CN (Cu-tpbn-Me2bpy, Me2bpy = 4,4′-dimethyl-2,2′-bipyridine), were prepared and their catalytic properties for ORR studied. All three complexes were homogeneous electrocatalysts for ORR in neutral phosphate buffer solutions. The ORR mediated by Cu-tpbn-Me2bpy had the most positive onset potential of 0.461 V vs RHE. In the applied potential window of -0.19 – 0.50 V vs RHE, Cu-tpbn boosted the stepwise four-electron ORR to mainly produce H2O, whereas Cu-tpbn-bpy and Cu-tpbn-Me2bpy mediated the ORR to mainly generate H2O2. The rate constants for the ORR to H2O promoted by Cu-tpbn, Cu-tpbn-bpy and Cu-tpbn-Me2bpy were 1.2 × 103 s−1, 3.2 × 10 s−1 and 7.8 × 10 s−1, respectively. The foot-of-the-wave analysis showed that the turnover frequencies for the reduction of O2 to H2O2 mediated by Cu-tpbn, Cu-tpbn-bpy and Cu-tpbn-Me2bpy were 1.5 × 104 s−1, 7.5 × 10 s−1 and 2.7 × 102 s−1, respectively. Meanwhile, complexes Cu-tpbn-bpy and Cu-tpbn-Me2bpy were more stable than Cu-tpbn. This work unveiled that the catalytic activity and the product selectivity of the ORR were greatly associated with the denticity, the steric effect and the electronic property of the organic ligands.

A novel Ga2O3-doped ZnO decorated SWCNT nanocomposite based amperometric sensor for efficient detection of dopamine in real samples

Our current research focuses on developing an efficient electrochemical Dopamine sensor for diagnosing neurological disorders related to abnormal Dopamine levels. We utilized a Ga2O3-doped ZnO decorated SWCNT (Ga2O3·ZnO@SWCNT) nanocomposite to modify a glassy carbon electrode. The structure and morphology of the Ga2O3·ZnO@SWCNT nanocomposite was examined utilizing a variety of approaches to ensure of their appropriateness as the sensing nanomaterial. The sensor effectively detects Dopamine within a wide range (1.0–2056 μM) in neutral phosphate buffer solution, exhibiting high sensitivity (0.2536 μAμM−1cm−2) and a practical detection limit (0.052 μM). It accurately quantifies Dopamine in human blood serum and commercial dopamine injection samples, displaying excellent reproducibility, repeatability, and stability. This proposed Dopamine sensor proves to be a reliable tool for Dopamine determination.

Low Overpotential Amperometric Sensor Using Yb2O3.CuO@rGO Nanocomposite for Sensitive Detection of Ascorbic Acid in Real Samples.

The ultimate objective of this research work is to design a sensitive and selective electrochemical sensor for the efficient detection of ascorbic acid (AA), a vital antioxidant found in blood serum that may serve as a biomarker for oxidative stress. To achieve this, we utilized a novel Yb2O3.CuO@rGO nanocomposite (NC) as the active material to modify the glassy carbon working electrode (GCE). The structural properties and morphological characteristics of the Yb2O3.CuO@rGO NC were investigated using various techniques to ensure their suitability for the sensor. The resulting sensor electrode was able to detect a broad range of AA concentrations (0.5-1571 µM) in neutral phosphate buffer solution, with a high sensitivity of 0.4341 µAµM-1cm-2 and a reasonable detection limit of 0.062 µM. The sensor's great sensitivity and selectivity allowed it to accurately determine the levels of AA in human blood serum and commercial vitamin C tablets. It demonstrated high levels of reproducibility, repeatability, and stability, making it a reliable and robust sensor for the measurement of AA at low overpotential. Overall, the Yb2O3.CuO@rGO/GCE sensor showed great potential in detecting AA from real samples.

Perylene derivative and persulfate as highly efficient electrochemical system for constructing sensitive amperometric aptasensor

To design highly efficient electrochemistry system was important for construct simple and sensitive biosensors, which was crucial in clinical diagnosis and therapy. In this work, a novel electrochemistry probe N,N′-di (1-hydroxyethyl dimethylaminoethyl) perylene diimide (HDPDI) with positive charges was reported to show two-electron redox behavior in neutral phosphate buffer solution between 0 and -1.0 V. And K2S2O8 in solution could significantly increase the reduction current of HDPDI at −0.29 V, which was interpreted with cyclic catalysis mechanism of K2S2O8. Moreover, HDPDI as electrochemical probe and K2S2O8 as signal enhancer was used to design aptasensors for protein detection. Thrombin was used as target model protein. Thiolate ssDNA with thrombin-binding sequence was immobilized on gold electrode to selectively capture thrombin and adsorb HDPDI. The thiolate ssDNA without binding with thrombin was with random coil structure and could adsorb HDPDI through electrostatic attraction interaction. However, the thiolate ssDNA binding with thrombin became G-quadruplex structure and hardly adsorbed HDPDI. Thus, with increasing the concentration of thrombin, the current signal stepwisely decreased and was taken as detection signal. Compared with other aptasensors based on electrochemistry molecules without signal enhancer, the proposed aptasensors exhibited wider linear response for thrombin between 1 pg mL−1 and 100 ng mL−1 with lower detection limit 0.13 pg mL−1. In addition, the proposed aptasensor showed good feasibility in human serum samples.

In-situ scalable fast fabrication of Cu-Cu2+1O nanorods for highly efficient electrocatalytic reduction into ammonia under neutral medium

The development of a highly efficient and durable electrocatalyst for nitrate reduction reaction (NO3RR) wastewater valorization to ammonia (NH3) is a promising strategy. However, it is challenging to design scalable low-cost electrocatalysts with high activity, high selectivity, and long-term stability by a facile and simple method. Herein, we construct this scalable Cu-based nanoarray with muti-oxidation states grown directly on nickel foam (NF) substrate (Cu2+1O@Cu/NF) using a facile molten salt method combined in-situ electrochemical reduction. The as-prepared Cu2+1O@Cu/NF nanoarrays reveal a high NH3 yield of 20.14 mg h−1 cm−2 at −0.95 V vs. a reversible hydrogen electrode (vs. RHE), Faradaic efficiency of 99.38% at −0.55 V vs. RHE in the neutral potassium phosphate (PBS) buffer solution with 50 mM NaNO3, which is ascribed to its electron redistribution with abundant oxygen vacancies and favorable charge/mass transfer.

Surface structure-sensitivity dependence and mechanistic study of the glucose electro-oxidation on Pt stepped surfaces in neutral solution (pH 7)

• Glucose electro-oxidation in neutral solution is a sensitive-structure reaction. • On Pt-[( n )(1 1 1)x(1 0 0)]: when n ≥ 9 , [1 0 0] steps favor more energetic reactions pathways. • As higher the [1 0 0] steps density on (1 1 1) terraces, lower is the catalytic activity. • On narrow (1 0 0) terraces, [1 1 1] steps conduce the reaction through less poisoned path. • [1 1 0] steps sites favor the CO L adsorption, especially as narrower as the surface is. The electro-oxidation of glucose (0.01 M) in a neutral solution phosphate buffer solution – pH ∼ 7 (0.1 M) is strongly sensitive to the surface structure. On surfaces containing (1 0 0) terraces domains the reaction occurs mainly into these sites due to their higher activity. Higher (1 1 1) step density into (1 0 0) terrace domains conducts the reaction through a less poisoned and energetic pathway because steps inhibit the cyclic carbonate formation. On surfaces containing (1 1 1) terrace sites, on large atom-wide terrace ( n ≥ 9 ) the reactivity of the (1 0 0) steps seems to be mainly associated to the anticipation of the formation of glucuronic acid and favor its oxidation to glucaric acid and/or xylonic acid + CO, that are more energetic reactions. On the other hand, when the step density is increased, the catalytic activity decreases as result of adsorption of intermediates and/products generated during the reaction on (1 0 0) steps. Lower and medium (1 1 0) density steps favor the adsorption of glucose on surfaces containing (1 1 1) terraces symmetry, but independently of the terrace step symmetry, as the (1 1 0) step density is increased the electrocatalytic activity is reduced because the reaction takes place through a more poisoned pathway, with the formation of a greater amount of species that adsorb strongly on the (1 1 0) sites and block the surface.

Light-activated antibacterial electrospun polyacrylonitrile-graphene quantum dot nanofibrous membranes

Polyacrylonitrile (PAN) nanofibrous membranes incorporating graphene quantum dots (GQD) as photoantibacterial additives were prepared by electrospinning. GQD encapsulation in the composite GQD-PAN membranes proved very stable, with negligible GQD leakage after 1 month immersed in neutral phosphate buffer solutions. A series of GQD-PAN membranes with different GQD content and electrospinning times were prepared to assess the influence of these parameters on the antibacterial activity of the membranes against Escherichia coli under visible light irradiation. Electrospinning time had a pronounced effect on membrane weight/thickness and nanofiber diameter, both parameters increasing with electrospinning time. Membranes with the optimal composition (1% wt. GQD and 1.5 h electrospinning time) showed excellent antibacterial activity against E. coli, with 99.9999% (6 logaritmic units) bacterial inactivation after 24 h illumination with visible light. Different bactericidal reactive oxygen species (ROS) were detected upon illumination of GQD solutions and GQD-PAN membranes, confirming photodynamic inactivation of the bacteria by GQD photosensitization. In terms of ROS production, GQD outperformed well-known photosensitizers crystal violet and toluidine blue O, both with long-established efficiency for photodynamic treatment of drug-resistant bacterial infections.

Self-Co-Electrolysis for Co-Production of Phosphate and Hydrogen in Neutral Phosphate Buffer Electrolyte.

The spontaneous reaction between Zn and H2 O is of critical importance and could plausibly be used to produce H2 gas, especially under neutral conditions. However, this reaction has long been overlooked owing to its sluggish kinetics and Zn consumption. Herein, a unique self-co-electrolysis system (SCES) is reported, which uses a Zn anode, a CoP-based catalytic cathode, and a neutral phosphate buffer solution (PBS) as the electrolyte. In this SCES, Zn is not only a sacrificial anode but also an important precursor of high-value-added NaZnPO4 . Additionally, the composition and phase structure of NaZnPO4 can be well regulated. In this study, a high-performance N,Cu-CoP/carbon cloth (CC) catalyst is synthesized to catalyze the cathodic hydrogen evolution reaction (HER) at an especially low overpotential of 64.7 mV at 10 mA cm- 2 . H2 gas (13.7 mL cm- 2 h- 1 ) and NaZnPO4 (3.73 mg cm- 2 h- 1 ) are obtained at the cathode and anode, respectively, in the N,Cu-CoP/CC||Zn SCES spontaneously. Moreover, the SCES has a favorable open-circuit voltage (OCV) of 0.79 V and a maximum power density of 1.83 mW cm- 2 . Density functional theory (DFT) calculations are performed to elucidate the electronic structure and HER catalytic mechanism of the N and Cu co-doped CoP catalysts.

The Effects of Potential and pH on the Adsorption of Guanine on the Au(111) Electrode.

The adsorption of nucleobase at a gold electrode has been a model system to study the interaction between biomolecule and metal, which is relevant to the development of sensors and molecular electronics. The current study has employed in situ scanning tunneling microscopy (STM) and voltammetry to investigate the adsorption configuration and spatial structure of guanine (G) on a well-defined Au(111) electrode in perchloric acid (HClO4) and neutral phosphate buffer solution (PBS) containing 50 μM G. Potential control had a profound effect on the adsorption of the G molecule on the Au(111) electrode. No adsorption of G was observed at a potential more negative than 0 V in HClO4 and -0.2 V (versus Ag/AgCl) in PBS; shifting potential positively triggered a rapid adsorption of G to yield a well-ordered G array. Different spatial structures of G admolecules were imaged with STM in HClO4 and PBS, suggesting that ions in the electrolyte were important in this adsorption event. Shifting potential positively caused a more compact G adlayer with molecules adopting a tilted orientation. Meanwhile, G molecules continued to deposit on the Au(111) electrode leading to a multilayer G film. These processes were reversible to the potential modulation. G admolecules on the Au(111) electrode could be irreversibly oxidized in 0.1 M PBS, which resulted in a prominent peak at 0.74 V in the voltammogram. This oxidation process could be used to analyze the G molecule in a sample.

Photoelectrochemical glycerol oxidation on Mo-BiVO4 photoanodes shows high photocharging current density and enhanced H2 evolution.

Mo-doped BiVO4's lower efficiency can be attributed in part to exciton recombination losses. Recombination losses during photoelectrochemical water oxidation can be eliminated by using glycerol as a hole acceptor. This results in an enhanced photocurrent density. In this research, we present the synthesis of a Mo-doped BiVO4 photoelectrode with a greater photocurrent density than a traditional pristine photoanode system. Increased photon exposure duration in the presence of glycerol leads to 8 mA cm-2 increase in photocurrent density due to the creation of a capacitance layer and a decrease in charge transfer resistance on the photoelectrode in a neutral-phosphate buffer solution thus confirming the photo charging effect. Glycerol photooxidation improves the photoelectrode's rate of hydrogen evolution. Research into the effects of electrolyte and electrode potential on photoelectrodes has revealed that when the applied potential increases, the light absorbance behaviour changes following its absorption distribution over the applied potential. Under a transmission electron microscope (TEM), a unique dynamical crystal fringe pattern is found in the nanoparticles scratched from the photoelectrode.

Mechanism of water oxidation catalyzed by vitamin B12: Redox non-innocent nature of corrin ligand and crucial role of phosphate

Vitamin B12 (macrocyclic cobalamin) has been recently reported to be capable of electrochemically catalyzing water oxidation in a neutral phosphate buffer solution. In this work, density functional calculations were employed to elucidate the water oxidation mechanism catalyzed by vitamin B12. The calculations showed that the catalytic cycle starts from the L•-CoII-OH2 complex 1. A proton-coupled electron transfer process then leads to the formation of a L•-CoIII-OH complex 2, followed by another proton-coupled electron transfer event to afford a corrin ligand radical cation intermediate 3 (L•-CoIII-O•). The redox non-innocent nature of the corrin ligand plays an essential role in the oxidation process. 3 is capable of triggering the O-O bond formation via a water nucleophilic attack mechanism, in which a hydrophosphate dianion functions as a base to accept a proton from the water nucleophile. A dioxygen molecule is released after the oxidation of the CoIII-OOH intermediate. The rate-determining step was calculated to be the O-O bond formation with a total barrier of 16.5 kcal/mol. While the use of water molecules as the proton acceptor was found to be less feasible for the O-O bond formation, with a barrier of 31.2 kcal/mol, further highlighting the crucial of phosphate in water oxidation.

Study of pH-Responsive and Polyethylene Glycol-Modified Doxorubicin-Loaded Mesoporous Silica Nanoparticles for Drug Delivery.

Tumor-targeted drug delivery systems represent challenging and widely investigated strategies to enhance cancer chemotherapy. In this study, we introduce a novel high-hydrophilic mesoporous silica nanoparticle system with a pH-sensitive drug release. The resultant composite nanoparticles appear as spheres of uniform size (450±25 nm) with a porous structure, which enables a high drug-loading ratio. Through modification of chitosan and polyethylene glycol monomethyl ether, the modified mesoporous silica was non-toxic to normal cells, but effective at inducing tumor cell death. With regard to the characteristics of drug release, the modified mesoporous silica clearly displayed a pH-stimulated release of the model drug doxorubicin hydrochloride in an acidic phosphate buffer solution (pH 4.0 and 6.0). The release was much greater than that observed in neutral or alkaline phosphate buffer solutions (pH 7.3 and 8.0). Furthermore, the release behavior was in accordance with the Higuchi model, indicating that this modified mesoporous silica drug delivery system can exhibit controlled release. The above results imply that the modified mesoporous silica is an effective drug delivery system for cancer therapy.

Boosting the Activity and Stability of Copper Tungsten Nanoflakes toward Solar Water Oxidation by Iridium-Cobalt Phosphates Modification

Severe interfacial electron–hole recombination greatly limits the performance of CuWO4 photoanode towards the photoelectrochemical (PEC) oxygen evolution reaction (OER). Surface modification with an OER cocatalyst can reduce electron–hole recombination and thus improve the PEC OER performance of CuWO4. Herein, we coupled CuWO4 nanoflakes (NFs) with Iridium–cobalt phosphates (IrCo-Pi) and greatly improved the photoactivity of CuWO4. The optimized photocurrent density for CuWO4/IrCo-Pi at 1.23 V vs. reversible hydrogen electrode (RHE) rose to 0.54 mA∙cm−2, a ca. 70% increase over that of bare CuWO4 (0.32 mA∙cm−2). Such improved photoactivity was attributed to the enhanced hole collection efficiency, which resulted from the reduced charge-transfer resistance via IrCo-Pi modification. Moreover, the as-deposited IrCo-Pi layer well coated the inner CuWO4 NFs and effectively prevented the photoinduced corrosion of CuWO4 in neutral potassium phosphate (KPi) buffer solution, eventually leading to a superior stability over the bare CuWO4. The facile preparation of IrCo-Pi and its great improvement in the photoactivity make it possible to design an efficient CuWO4/cocatalyst system towards PEC water oxidation.

Electrocatalytic performance and cell voltage characteristics of 1st-row transition metal phosphate (TM-Pi) catalysts at neutral pH

Water electrolysis represents a clean and sustainable route for large-scale hydrogen generation. However, efficient water splitting is hindered by the kinetically sluggish oxygen evolution reaction (OER), which requires significant energy inputs to drive the reaction at sufficiently fast rates. Recently, an increasing number of applications have emerged that require water electrolysis at neutral pH and under ambient conditions. This requirement creates additional challenges as the electrolysis of water is favorable in acidic and alkaline conditions. In order to tackle these challenges, considerable efforts have been devoted to the development of earth-abundant, highly effective, and robust electrocatalysts for the OER at pH = 7. Of these catalysts, amorphous transition-metal phosphates have attracted wide attention because of their unique electrocatalytic properties. In this paper, the OER performance of a series of amorphous first-row transition metal phosphate (TM-Pi) catalysts, namely Co-Pi, NiFe-Pi and Fe-Pi prepared with different deposition strategies onto various substrates, is comparatively studied in a neutral phosphate buffer solution (PBS). Additionally, a simplified cell model is applied to analyze the current-voltage characteristics and quantitatively evaluate and compare the reversible, ohmic, and activation overvoltage components of the studied TM-Pi. It is found that TM-Pi catalysts deposited onto a highly ordered nickel foam (NF) substrate are competitive with commercial Pt and IrO2 catalysts in terms of OER activity and long-term stability.

The medium effect on electrodissolution of adsorbed or suspended Ag nanoparticles

Electrochemical behaviour of six types of Ag nanoparticles (three stabilised by citrate and three others stabilised by polymers) was studied on carbon screen-printed electrode and glassy carbon rotating disc electrode. A stationary electrode was used as a support for adsorbed nanoparticles, whereas the rotating disc electrode was applied for experiments in nanoparticles suspension. Peak shaped cyclic voltammograms obtained for immobilised nanoparticles indicate their electro-dissolution and electrodeposition of silver in the backward scan. The given peak shape and its position on potential scale depend both on the type of nanoparticles and the supporting electrolyte. When aggregation of Ag nanoparticles was detected by UV–vis spectroscopy, splitting of an anodic peak corresponding to electrodissolution of silver in neutral phosphate buffer or NaOH solution is seen. Injection of a fraction of microgram of Ag nanoparticles was detected in chronoamperometric experiments on rotating disc electrode. However, in the presence of H2O2, the effect of nanograms of silver was seen on voltammetric curve indicating electrocatalytic amplification.

The Immunological Study of Salmonella Infantis in white Mice Immunized with Killed Antigen

The present study was carried out to investigate the effect of formalin-killed antigen for Sallmonellainfantis in vivo with the study of cellular immune response through the study of cytokines.Sallmonellainfantis were isolated and diagnosed from local milk products (milk and cheese). 74 milk samples and 53 cheese samples were taken.The media were usedgeneral and special culture media as well as biochemical tests were used to diagnose the isolates and the diagnosis was confirmed by using API 20. Sallmonellainfantis antigens were used systemically. 50 Swiss white mice of both sexes were randomly divided into three groups. The first group prevented (20 mice) with the bacterial antigen killed by formalin in a dose (0.3) I.P for each animal. The group was injected with a booster dose and the same first immunization dose two weeks after the first dose. The second group (20 mice) and the third group (10 mice) were counted as positive and negative control groups respectively. The first group and the second group received a dose of 0.3 ml of stuck S.infantis containing (1×108 live cells / ml) I.P, while the third group injected 0.3 ml of neutral phosphate buffer solution under the skin. The results showed that 4 animals from the first group were killed and all the remaining animals from the first group were killed 20 days after the challenge dose and serum was taken to measure cellular immunity. The results of serological tests showed that the level of (IL-4 and IL-6) were (38.48 ± 2.1 and 31.81, 3.01) respectively, as well as the results of measurement of concentration (INF gamma and TNF-?) were (401 ± 2.12 and 173.421 ± 3.11) respectively.We conclude from the study that there was a high percentage of S.infantis isolated from milk products as well as we conclude that the formalinS.infantiskilledantigen partially protected against the infection.