Metal Salt Concentration Research Articles

Facile synthesis of Ni-incorporated and nitrogen-doped reduced graphene oxide as an effective electrode material for tri(ammonium) phosphate electro-oxidation

Drying well-mixed Ni(CH3COO)2-PVP solution results in incorporation of metal precursor NPs throughout the polymer sheets. Adjusting the metal salt content leads to produce N-doped and Ni-decorated rGO which is an effective electrocatalyst for H2 production from tri(ammonium) phosphate.

Biosynthesis, characterization, and evaluation of antibacterial and photocatalytic methylene blue dye degradation activities of silver nanoparticles from Streptomyces tuirus strain

Silver nanoparticles (AgNPs) are a promising technology for the design of antimicrobial agents against drug-resistant pathogens. It could also be used for the photocatalytic degradation of dyes used in industries such as methylene blue (MB). In this study, 17 different actinomycetal strains isolated from hydrocarbon-contaminated soils collected from an oil distribution company in Algeria were evaluated for their ability to produce NPs. After a selection process, S16 was the main strain capable of synthesizing AgNPs extracellularly. The strain S16 was determined using molecular identification based on the sequencing of the 16S rDNA gene. Among various techniques used for the synthesis of AgNPS, a technique using a temperature of 30 °C, pH of 7, a metal salt concentration of 1 mM, and a period of 72 h in the dark were found to be more effective in the biosynthesis of the AgNPs. The biosynthesized AgNPs that were analyzed by UV–visible spectroscopy resulted in a specific peak at a wavelength of (λ = 400 nm). The DRX analyses showed characteristic peaks of the AgNPs at (1 1 1), (2 0 0), (2 2 2), and (3 1 1), which validated the presence and crystalline nature of the biosynthesized NPs. Zetasizer analysis showed an average size and zeta potential of 64 nm (−32.3 mV), while the SEM-EDS analysis confirmed the spherical shape of AgNPs and the presence of Ag atoms in the elemental composition. The biosynthesized AgNPs indicated adequate antibacterial activity against 5 out of the 6 strains tested in this study, using minimum inhibitory concentration (MIC) that ranged from 217.18 μg/mL to 1137.5 μg/mL. The AgNPs were combined with commercial antibiotics and the synergistic effect of the combination was also assessed against MRSA which resulted in increased antibacterial activity of AgNPs in the presence of the strain S16. Furthermore, the photocatalytic degradation of the methylene blue (MB) was evaluated under sunlight and UV irradiations using biosynthesized AgNPs. The AgNPs showed photocatalytic decolorization potential of 71.3% for MB dye (20 ppm) under sunlight irradiation within 6 h of incubation, while only 11.25% of the MB dye degraded using UV irradiation.

Sensing of Transition Metals by Top-Down Carbon Dots

Carbon quantum dots (CQDs) are a new class of carbon-rich materials with a range of unique optical and structural properties. They can be defined as carbon nanoparticles, with sizes in the range of 1–10 nm, displaying absorption and emission activities in the UV-VIS range. Depending on the structure, CQDs display a wide variability of properties, which provides the possibility of finely tuning them for several applications. The great advantages of CQDs are certainly the ease of synthesis, non-toxicity, and the strong interactions with the surrounding environment. Based on this, CQDs are especially promising as selective chemosensors. The present study reports on carbon quantum dots synthesized with a top-down (TD) approach, and characterized by different optical, spectroscopic, and morphological techniques to identify the selectivity for metal ions belonging to the first transition series. In particular, the study focuses on the interaction between two samples, namely TD and TDA, featuring different surface functionalization, and heavy metal ions. Their sensing towards Co2+, Cu2+, Fe3+, Zn2+, and Ni2+ has been tested by fluorescence (PL), steady state absorption spectroscopy, and time-resolved PL spectroscopy, in order to determine the fluorescence quenching. We found a PL quenching in the presence of concentrations of metal salts starting from 0.5 µM, and a selectivity towards the interacting ions, depending on CQDs’ surface features paving the way for their use for sensing.

Superhydrophilic-underwater superoleophobic NiO nanostructured surfaces: Assessment of PVP concentration effect

In this research, superhydrophilic-underwater superoleophobic NiO and nickel oxalate micro/nano structured thin films on the stainless steel (SS) meshes have been fabricated via chemical bath deposition (CBD) as a facile route. Taguchi L16 experimental design was used for optimization the effects of six important influential parameters affecting the surface wettability including molar ratio of alkaline to metallic precursor salt, alkaline agent type, NiO seed layer solution concentration, seed layer type, Polyvinylpyrrolidone (PVP) concentration and precursor type. Effect of the PVP concentration (as additive) on the oil contact angle was evaluated for the first time. The molar ratio of the alkaline to metallic salt and PVP concentration were the two most important factors having the highest impact on the underwater oil repellency behavior. The sample prepared under the optimum conditions exhibited underwater superoleophobicity with the oil contact angle (OCA) of 156.15 ± 7.5° and oil contact angle hysteresis (OCAH) of 4.3°. The X-ray diffraction (XRD) analysis, Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FE-SEM), and roughness measurements were applied for characterization of the fabricated samples. Based on the FESEM analysis, the spherical nano- ZnO seeds have diameters of ~30–50 nm. In addition, the abrasion test was accomplished (12 cycles under 4.7kPa). The obtained results showed an excellent mechanical robustness. Moreover, an acceptable chemical durability (after 240 h) in acidic and alkaline environments with pH values of 4, 6 and 12 was observed.

Tuning the nano-porosity and nano-morphology of nano-filtration (NF) membranes: Divalent metal nitrates modulated inter-facial polymerization

Divalent metal nitrates were pre-loaded on polysulfone support to modulate the interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC). It is found that the nano-porosity and nano-morphology of thus formed thin film composite polyamide (TFC-PA) nano-filtration (NF) membranes as well as their filtration performance could be effectively tuned by the type and concentration of the divalent metal salts, especially the divalent cations used. Main group cations, such as Mg (II) and Ca (II), increased the water flux of the NF membranes by increasing their surface nano-scale nodular arrays without altering the pore sizes and rejections of the membranes, while transitional metal cations such as Zn (II), Cu (II) and Co (II) increased the water flux of the NF membranes not only by the formation of high surface area nano-scale Turing type crisscrossed ridge networks, but also by the increase of their nano-pore sizes due to their coordination with the >NH groups of the PIP. The prepared NF membranes pore sizes adjustable from 0.54 Å to 0.90 Å could be developed to have varied selectivity and rejections among inorganic salts and organic dyes.

Patch test-relevant concentrations of metal salts cause localized cytotoxicity, including apoptosis, in skin ex vivo.

BackgroundMetal alloys containing contact sensitizers (nickel, palladium, titanium) are extensively used in medical devices, in particular dentistry and orthopaedic surgery. The skin patch test is used to test for metal allergy.ObjectiveTo determine whether metal salts, when applied to freshly excised skin at patch test–relevant concentrations and using a method which mimics skin patch testing, cause in changes in the epidermis and dermis.MethodsTissue histology, apoptosis, metabolic activity, and inflammatory cytokine release were determined for two nickel salts, two palladium salts, and four titanium salts.ResultsPatch test–relevant concentrations of all metal salts caused localized cytotoxicity. This was observed as epidermis separation at the basement membrane zone, formation of vacuoles, apoptotic nuclei, decreased metabolic activity, and (pro)inflammatory cytokine release. Nickel(II) sulfate hexahydrate, nickel(II) chloride hexahydrate, titanium(IV) bis(ammonium lactato)dihydroxide, and calcium titanate were highly cytotoxic. Palladium(II) chloride, sodium tetrachloropalladate(II), titanium(IV) isopropoxide, and titanium(IV) dioxide showed mild cytotoxicity.ConclusionThe patch test in itself may be damaging to the skin of the patient being tested. These results need further verification with biopsies obtained during clinical patch testing. The future challenge is to remain above the elicitation threshold at noncytotoxic metal concentrations.

A near-zero-waste approach using simple physical-chemical methods recovery high concentrations of ammonia nitrogen, heavy metal, and sodium salts from hazardous vanadium-extracted solution

An integrated simple physical-chemical method was proposed to realize the comprehensive utilization of valuable resources from vanadium-extracted solution. The hazardous vanadium-extracted solution contains high concentrations of Cr(VI), ammonia nitrogen, sodium salt, and silicic acid. Firstly, a series of operations include reduction-precipitation, calcination, and leaching were used to recover high concentration Cr(VI), and 99.96% of Cr(VI) was recovered as chromium oxide with the purity of 97.24%. Optimum conditions for the reduction pH, amount of sodium sulfite, precipitation pH, and precipitation time were 2.0, 1.2 times theoretical, 7.3, and 15 min, respectively. Secondly, clean ammonia nitrogen recovery through waste heat distillation was realized. And the total recovery efficiency of ammonia nitrogen was 95.6% at pH = 11.0, distillation 50 min with 0.5M sulfuric acid as the absorption liquid. Also, the distillation residue sodium sulfate was concentrated and purified by distillation. Finally, all the resources were separated efficiently and could be reused back into the upstream vanadium extraction process, achieving resource recycling. Moreover, material balance, energy analysis and the flow chart of the near-zero-waste approach for resource recycling from the hazardous vanadium-extracted solution were concluded.

Multilayer Langmuir-Blodgett thin films studies for chemical sensors development

This paper presents the study of the development of complex organic materials deposited by the Langmuir Blodgett technique. We have synthetized Langmuir Blodgett multilayers for the recognition of toxic chemicals in the air and / or ultraviolet radiation. The sensitive materials are based on multilayers of stearic acid metal salts combined with nanocarbon and metalloporphyrin structures. We prepared and obtained by the Langmuir Blodgett method films with nano-metric thicknesses combined in different concentrations of metal salts of fatty acids, Nano carbon structures and metalloporphyrins. Further we have characterized and tested the materials obtained for the sensitivity and selectivity of multilayers under the influence of various toxic gases and / or ultraviolet radiation obtaining high results in the field of sensors.

A Review on Synthesis of Plant-Mediated Metal Nanoparticles for Fabric Coating

Biosynthesis, or also known as green synthesis method, has received an enormous attention from the scientific community over the physical and chemical synthesis methods for the production of metal or metal oxide nanoparticles (NPs). Physical and chemical syntheses are typically expensive and generate a large number of hazardous by-products which can cause toxicity to either humans or the environment. Thus, biosynthesis is an alternative for production of NPs. Biosynthesis involves the use of plant extracts and natural bio-resources such as microorganisms and enzymes. It has been demonstrated that the biosynthesis method is suitable for large-scale production since it is simple, cheap, easy, fast, non-toxic, and environmentally friendly. This review mainly focuses on the synthesis of plant-mediated metal NPs for fabric coating. Importantly, the characteristics of the NPs and their applications after fabrication onto the fabrics are also highlighted. The morphology and size of the NPs are influenced by the concentration of plant extracts, control of metal salt concentration, temperature, and pH. This review also summarizes the advantages, limitations, and future challenges of biosynthesis towards the production of fabric coatings. There are several advantages in utilizing green substances, including moderate operation conditions with a minimal use of toxic chemicals and low energy consumption.

Sustainable detection and capturing of cerium(III) using ligand embedded solid-state conjugate adsorbent

The detection, adsorption and recovery of rare-earth elements specially the cerium (Ce(III)) on ligand based optical conjugate adsorbent was systematically studied. The functional ligand of 6-((2-(2-hydroxy-1-naphthoyl)hydrazono) methyl)benzoic acid (HMBA) was synthesized and then successfully anchored onto mesoporous silica by a direct immobilization method for the fabrication of conjugate adsorbent. The Ce(III) ion was detected by the charge transfer (π–π transition) transduction mechanism with high sensitivity and selectivity. The experimental conditions were optimized based on contact time, solution acidity, initial Ce(III) concentration and pH acidity and diverse metal salt concentrations. The conjugate adsorbent was highly sensitive, and the limit of detection was 0.33 µg/L for Ce(III) ions. The Ce(III) adsorption from synthetic aqueous solution also underwent in batch mode. However, the adsorption capacity depended on the solutions pH, initial concentration and to some extent on the competing ions. The experimental data revealed that the maximum Ce(III) adsorption was possible at pH 5.0. The presence of other cations and anions did not adversely affect the Ce(III) capturing by the conjugate adsorbent. The maximum adsorption capacity was determined to be as high as 179.16 mg/g. The extraction and recovery of Ce(III) ions from the saturated adsorbent was possible with 0.20 M HNO3. The regenerated adsorbent that remained maintained the high selectivity to Ce(III) ions and exhibited almost the same capturing ability as that of the original adsorbent. However, the adsorption efficiency was slightly decreased after several cycles. Therefore, the proposed conjugate adsorbent offered a cost-effective adsorbent and may be considered a viable alternative for effectively detection, capturing and recovery of Ce(III) ions from wastewater samples.

Synthesis of intracellular and extracellular gold nanoparticles with a green machine and its antifungal activity.

Green synthesis method is being increasingly used in the development of safe, stable, and eco-friendly nanostructures with biological resources. In this study, extracellular and intracellular synthesis of gold nanoparticles (AuNPs) was carried out using green algae Chlorella sorokiniana Shihira & R.W. Fresh algae were isolated and identified from Musaözü Pond located in the province of Eskişehir and then extraction process were performed. Optimization studies were studied using pH value, metal salt concentration, and time parameters for extracellular synthesis and using only time parameter for intrasellular synthesis. Since more controlled and optimum conditions can be achieved in the production of AuNPs by extracellular synthesis, these nanoparticles (NPs) were used for characterization and antifungal activity studies. Optical, physical, and chemical properties of synthesized NPs were characterized by UV visible spectrophotometer (UV-Vis), dynamic light scattering (DLS), Zetasizer, X-Ray diffraction (XRD), Fourier transform ınfrared spectroscopy (FTIR), field emission scanning electron microscope (FE-SEM), ınductively coupled plasma mass spectrometer (ICP-MS) and transmission electron microscope (TEM) analysis. The optimum conditions for AuNPs synthesis were determined as 1 mM for HauCl4 concentration, 6 for pH value, and 60th min for time. AuNPs obtained from extracellular synthesis from C. sorokiniana extract are 5–15 nm in size and spherical shape. TEM images of extracellular synthesis show noticeable cell wall and membrane damages, cytoplasma dissolutions, and irregularities. AuNPs obtained by intracellular synthesis are in 20–40 nm size and localized in the cell wall and cytoplasm. These NPs exhibited significant antifungal activity against C. tropicalis, C. glabrata, and C. albicans isolates. AuNPs obtained by algae-mediated green synthesis have a significant potential for medical and industrial use, and this eco-friendly synthesis method can be easily scaled for future studies.

Electrochemical water electrolysis using electrodeposited (NiMo) coatings from a low concentration bath

Electrodeposited (NiMo) coatings are noted as benign alternative for Pt-free electro-catalysts in alkaline water electrolysis. Hitherto, many Ni-based alloy coatings have been developed using baths of high salts’ concentration. The present paper attempts to see the effect of reducing the metal salt concentrations of a (NiMo) bath on the electro-catalytic functionality of its alloy coatings towards both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Electro-catalytic performance was evaluated through cyclic voltammetry (CV) and chronopotentiometric (CP) studies and the findings were compared with those obtained from high concentration bath, with the same constituents. It was revealed that the electro-catalytic efficacy of (NiMo) coatings has a direct relation only with the alloy composition, rather than the concentration of the bath, which is due to the inherent induced co-deposition behavior of (NiMo) system, supported by Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-Ray Spectroscopy (EDXS), and X-ray Diffraction (XRD) analyses.

Effects of heavy metals on physiological status for Schoenoplectus litoralis & Salvinia natans L

This study investigated the removal of three concentrations of heavy metal salts, namely nickel chloride, manganese chloride, cobalt chloride and zinc chloride in the Phytoremediation of two aquatic plants (Schoenoplectus litoralis and Salvinia natans), and the determination of the level of total chlorophyll and protein by the exposure to two water plants (Schoenoplectus litoralis and Salvinia naturalans). Two samples of each plant were taken every ten days to determine the heavy metal, protein and chlorofyll after 30 days. The experiment was completed. At the end of the experiment, the results of the study showed different concentration levels of heavy metals in tissue in the plant and showed decreasing total chlorophyll and protein concentrations for the aquatic plant.

Fabrication of graphene oxide microcapsules based on Pickering emulsions for self-healing water-borne epoxy resin coatings

Metallic iron oxide nanoparticle-modified graphene oxide (GO) sheets were well applied for stabilizing oil-in-water (O/W) Pickering emulsion, because they were easy to fabricate via a redox reaction between metal salt and GO nanosheets. A systematical investigation was conducted on the impacts of metal salt concentration for preparing the nanoparticle-modified GO, GO aqueous dispersion concentrations and the mass ratios of GO/oil phase on the characteristics of Pickering emulsion. As revealed from the outcomes, the graphene oxide encapsulated GMA microcapsules (GMA@GOMCs) exhibited high loading capacity and thin shell thickness. Then, the microcapsules were embedded into water borne epoxy matrix and fabricated the coating which were capable of healing themselves over surface of hot-dip galvanized steels, as only supplementing a less amounts of microcapsules might achieve almost repaired completely. It’s expected that the GOMCs based on Pickering emulsions can be applicable in a wide range of applications, such as automotive field, weather and marine environments.

Analysis of key factors in the coagulation of metal salts based on the calculation of hydrolysis-precipitation distribution

Hydrolysis and precipitation are the key processes that determine the coagulation performance of inorganic metal salts. The valence and concentration of metal salts, ligands, and solution pH all influence the coagulation performance. In order to get a full picture on the pros and cons of various inorganic metal salts as coagulants, this paper conducted thermodynamic equilibrium calculations and coagulation experiments to analyze and verify the hydrolysis-precipitation areas and speciation of four inorganic metal salts (aluminum, iron, titanium, and zirconium) in the absence and presence of ligands. In addition, the contributions of polynuclear hydrolysates in the hydrolysis and precipitation of the four metal ions were quantitatively described. Furthermore, the underlying mechanisms of the effects of common aquatic ligands on coagulation performance were discussed from the perspective of solution chemistry. The above results provide a theoretical basis for the development and application of inorganic metal salt coagulants, and are of great significance for understanding the coagulation performance and mechanisms accurately.

Molecular cannibalism: Sacrificial materials as precursors for hollow and multidomain single crystals

The coexistence of single-crystallinity with a multidomain morphology is a paradoxical phenomenon occurring in biomineralization. Translating such feature to synthetic materials is a highly challenging process in crystal engineering. We demonstrate the formation of metallo-organic single-crystals with a unique appearance: six-connected half-rods forming a hexagonal-like tube. These uniform objects are formed from unstable, monodomain crystals. The monodomain crystals dissolve from the inner regions, while material is anisotropically added to their shell, resulting in hollow, single-crystals. Regardless of the different morphologies and growth mechanism, the crystallographic structures of the mono- and multidomain crystals are nearly identical. The chiral crystals are formed from achiral components, and belong to a rare space group (P622). Sonication of the solvents generating radical species is essential for forming the multidomain single-crystals. This process reduces the concentration of the active metal salt. Our approach offers opportunities to generate a new class of crystals.

Removal of Cadmium and Chromium by Mixture of Silver Nanoparticles and Nano-Fibrillated Cellulose Isolated from Waste Peels of Citrus Sinensis.

Nano-fibrillated cellulose (NFC) was extracted by a chemical method involving alkali and acid hydrolysis. The characterisation of the citrus sinensis fruit peel bran and nano-fibrillated cellulose was performed by XRD, FTIR, TEM, and FESEM. XRD confirmed the phase of NFC which showed monoclinic crystal with spherical to rod shape morphology with a size of 44–50 nm. The crystallinity index of treated NFC increased from 39% to 75%. FTIR showed the removal of lignin and hemicellulose from waste peels due to the alkaline treatment. Silver nanoparticles were also synthesised by utilizing extract of citrus sinensis skins as a reducing agent. Pharmaceutical effluent samples from an industrial area were tested by Atomic Absorption Spectrometry. Out of the four metals obtained, cadmium and chromium were remediated by silver nanoparticles with nano-fibrillated cellulose via simulated method in 100 mg/L metal-salt concentrations over a time period of 160 min. The highest removal efficiency was found for cadmium, i.e., 83%, by using silver and NFC together as adsorbents. The second highest was for chromium, i.e., 47%, but by using only NFC. The Langmuir and Freundlich isotherms were well fitted for the sorption of Cd (II) and Cr (II) with suitable high R2 values during kinetic simulation. Thus, the isolation of NFC and synthesis of silver nanoparticles proved efficient for heavy metal sorption by the reuse of waste skins.

Effect of Inoculating the Root System of Plants with Endophyte Cylindrocarpon magnusianum on Plant Performance When Exposed to Heavy Metal Salts

The effect of inoculation with endotrophic micromycete Cylindrocarpon magnusianum on the physiological and biochemical parameters of test tomato plants when exposed to heavy metal salts was studied. The experimental scheme included inoculation with a fungal culture (control population) and with populations of this fungus that were previously adapted to this stress factor. The inoculated plants were then grown under control conditions and on substrates with different concentrations of heavy metal salts (zinc, copper, lead, and chromium). No stimulating effect that increases the resistance of plants to heavy metal salts after inoculation of plants by the control population of the fungus C. magnusianum was detected. When using nonbiogenic chemical elements, adaptive plant responses associated with the content of photosynthetic pigments in leaves and the formation of plant biomass were significantly expressed when plants were inoculated with adapted fungal populations of C. magnusianum and when they were further cultivated on substrates introduced with chromium and lead salts. Under these conditions, the fungal infection in plant roots was more intense compared to the use of the control population of the fungus. These facts indicate the more efficient partnership of the fungus C. magnusianum and the root system of plants under conditions that are extreme for plant life.

A laccase Gl-LAC-4 purified from white-rot fungus Ganoderma lucidum had a strong ability to degrade and detoxify the alkylphenol pollutants 4-n-octylphenol and 2-phenylphenol

In this study, the ability of laccase Gl-LAC-4, purified from Ganoderma lucidum, to degrade and detoxify two representative alkylphenol pollutants, 4-n-octylphenol and 2-phenylphenol, was systematically studied. Gl-LAC-4 laccase had a very strong ability to degrade high concentrations of 4-n-octylphenol, 2-phenylphenol, and alkylphenol mixtures. The degradation speed of Gl-LAC-4 toward 2-phenylphenol was very fast. Gl-LAC-4 displayed strong tolerance for a variety of metal salts and organic solvents in the degradation of alkylphenols. Gl-LAC-4 showed strong tolerance for high concentrations of various metal salts, such as MgSO4, MnSO4, Na2SO4, CuSO4, ZnSO4, CdSO4, and K2SO4, in the degradation of 4-n-octylphenol and 2-phenylphenol.In the case of the same metal cation, the inhibitory effect of the metal salt with Cl− as the anion on the degradation of 4-n-octylphenol and 2-phenylphenol by laccase was stronger than that of the metal salt with SO42− as the anion. An increase in the number of chloride ions caused a greater inhibitory effect on alkylphenol degradation by laccase. Gl-LAC-4 exhibited strong tolerance for glycerol, ethylene glycol, butanediol, propylene glycol, and organic solvent mixtures in the degradation of alkylphenols. Gl-LAC-4 treatment significantly reduced or eliminated the phytotoxicity of 4-n-octylphenol and 2-phenylphenol.

REVIEW ON ROLE OF METAL SALT IN THE RE-MINERALIZATION OF DENTAL CARIES

Dental caries is a most common disease that affects large number of people. It is a worldwide public health problem, affecting numerous urban and rural communities. White-spot lesions (WSL) are the earliest macroscopic evidence of enamel caries. Typically, the enamel surface layer stays intact during subsurface demineralization, but, without treatment, will eventually collapse into a full cavity. Near-neutral pH of saliva is endowed with a natural buffering capacity. Natural demineralization of tooth at an early stage is reversed by saliva, which contains calcium ions, phosphate ions, buffering agents, fluoride, and other substances. The strategy for aided remineralisation is to have ions directly delivered to where and when they are needed the most. Several mechanisms are available for aided remineralisation. The most well known is the delivery of topical and systemic fluoride, which has been proven to be a highly effective measure for prevention of caries. However limitations and risks associated with the use of fluoride as a remineralising agent fuelled the need to develop newer non-toxic techniques that deliver calcium and phosphate ions directly into subsurface lesion and/or boost remineralising properties of saliva. Encouraging microscopic changes in the demineralized enamel surface following the treatment with different concentration of metal salts, involving zinc, strontium, magnesium, in addition to stannous fluoride, many metal salts are in use for the treatment of dental caries. Microscopic examination was conducted on teeth samples before and after pH-cycling procedure and following the treatment with the selected metal salt under polarized microscope (100X). The best obvious remineralisation was found following treatment with stannous fluoride, followed by zinc chloride. The stannous fluoride was the best in the remineralisation of initial caries, results for other metals seem to be promising if used for prevention of dental caries. Mineralization of teeth is determined by major inorganic elements as calcium, phosphorous in addition to other elements that occur in traces within tooth structure (Thylstrup and Fejerskov, 1996 Murry, 1996 Peter, 2004). Fluoride now a day is widely used either systemically or topically to increase resistance of teeth surface, it has been well documented as a major contributing factor in the decline of the incidence and severity of dental caries in many countries (Murry, 1996 Curzon,1999).So far fluoride has been considered to play an almost unique role in the prevention of dental caries however there is no reason to dismiss the role of other elements as being potential cariostatic agents. Different concentrations of different metal ions as zinc and copper have been tested for better effect on remineralisation in vitro (Dedhiya, et al., 1974 Fang et al., 1980). However controversy is present in the literature concerning their effectiveness in prevention of dental caries when used topically at effective concentrations (Torredo et al., 2004 Elzbieta et al., 2008 Curzon, 1983).