Ppm Ag Research Articles

Silver diamine fluoride in preventing enamel erosion: An in vitro study with salivary pellicle

ObjectivesTo compare the prevention of enamel erosion and discolouring effect with a single and two weekly topical applications of silver diamine fluoride (SDF) solution. MethodsHuman enamel blocks were divided into four groups. Group 1 (SDF2) received two weekly applications of SDF solution (Advantage Arrest: 260,000 ppm Ag, 44,300 ppm F, pH 9.1). Group 2 (SDF1) received a single application of SDF solution. Group 3 (SNF, Positive Control) received daily application of stannous-chloride/amine-fluoride/sodium-fluoride solution (Elmex® Enamel professional: 800 ppm Sn(II), 500 ppm F, pH 4.5). Group 4 (DW, Negative Control) received daily application of deionised water. The treated blocks were subjected to a 14-day erosive challenge. Crystal characteristics, elemental composition, surface morphology, percentage of surface microhardness loss (%SMHL), surface loss, and total colour change (ΔE) of the blocks were investigated using X-ray diffraction (XRD), energy-dispersive spectrometry (EDS) and scanning electron microscopy (SEM), Vickers’ hardness testing, non-contact profilometry, and digital spectrophotometry, respectively. ResultsXRD and EDS revealed precipitates of silver for SDF2 and SDF1 and tin for SNF. SEM showed prominent etched enamel pattern on DW than the other three groups. The%SMHL (%) of SDF2, SDF1, SNF, and DW were 26.6 ± 2.9, 33.6 ± 2.8, 38.9 ± 2.9, and 50.5 ± 2.8 (SDF2<SDF1<SNF<DW, p < 0.001). Surface loss (μm) of SDF2, SDF1, SNF, and DW were 3.1 ± 0.6, 3.9 ± 0.6, 3.9 ± 0.7, and 5.5 ± 0.8 (SDF2<SDF1=SNF<DW, p < 0.05). Colour change of SDF2, SDF1, SNF, and DW were 7.9 ± 3.9, 4.0 ± 3.6, 3.6 ± 3.5, and −4.4 ± 3.9 (SDF2>SDF1=SNF>DW, p < 0.05). ConclusionTwo weekly applications was more effective than a single application of SDF in preventing enamel erosion, though it caused more discolouration. Clinical significanceTopical application of 38 % SDF with two weekly applications protocol is effective in preventing enamel erosion.

Synthesis and synergistic effects of antibacterial and corrosion inhibition based on concentrated hydrosols of silver nanoparticles

A highly water-soluble and uniformly dispersed concentrate of silver nanoparticles (Ag NPs) hydrosols were synthesized using a chemical reduction method. The Ag NPs hydrosols exhibited remarkable antibacterial activity against sulfate-reducing bacteria (SRB) and can serve as a biocide for anti-corrosion purposes. The addition of 50 ppm Ag NPs hydrosols reduced the corrosion rate by over 91 % in the presence of SRB biofilm compared to untreated conditions. Numerous Ag NPs adsorbed onto the cell wall, with some internalizing and entering the cell, resulting in cytoplasmic efflux and DNA damage, ultimately leading to cell death.

In vivo Evaluation of Silver Nanoparticles on the Management of Meloidogyne incognita in Green Gram

In the investigations, on the effect of Ag NPs on the management of M. incognita in green gram, the results showed that all the treatments were found to be effective in increasing all growth parameters. Maximum growth parameter viz., plant height, fresh and dry weight of shoot and root were recorded in the treatment with 0.15 ppm Ag NPs + M. incognita. Maximum reduction in galls, egg masses and final nematode population in soil were recorded in the treatment with 0.15 ppm Ag NPs. All the treatments significantly differed from control except the treatment with 0.0015 ppm Ag NPs + M. incognita.

Genesis of sediment‐hosted copper and silver mineralization at the Omatapati prospect, Kaoko Belt, Opuwo district, Kunene region, Namibia

AbstractThe Omatapati copper and silver prospect within the Kaoko Belt is located in the Opuwo district, Kunene region, Namibia. The prospect is hosted by dolomite and interbedded argillites of the Neoproterozoic Devede Formation, the Ombombo Subgroup. An ore body is exposed in shallow artisanal mining pits and drill‐cores of the prospect have grades of 0.4 to 5.2 wt% Cu, and 23 to 312 g/t Ag. The prospect was formed by both hypogene and supergene mineralization processes. The hypogene mineralization occurred in three stages. Stage 1 is represented by calcite veins containing chalcopyrite, bornite, sphalerite and galena. Stage 2 consists of quartz and calcite veins with chalcopyrite and bornite. Stage 3 consists of quartz‐calcite‐barite veins with chalcopyrite. The veins of stages 1 and 2 are subparallel or discordant to the foliation of argillites, and those of Stage 3 are NE‐striking and steeply dipping in the brecciated dolostone and argillite. The mineralization stages 1, 2, and 3 are overprinted by supergene chalcocite, digenite, annite, covellite, malachite, delafossite, hematite, and goethite. The supergene process forms a semi‐massive chalcocite‐covellite zone, which extends from the surface to ~50 m depth. The veins show average concentrations of 2.1 wt% Cu, 80 ppm Ag, and 532 ppm Pb for the stage 1, 3.1 wt% Cu, 118 ppm Ag, and 66 ppm Pb for the stage 2, and 18.6 wt% Cu, 675 ppm Ag, and 565 ppm Pb for the Stage 3 with supergene overprinting. Silver occurs as impurity in supergene chalcocite (6303 ppm Ag), digenite (4425 ppm Ag), and covellite (3060 ppm Ag). Fluid inclusions in quartz and calcite revealed that the hypogene mineralization occurred under a pressure &gt;7–8 MPa. Temperatures of ore formation of the stages 1, 2, and 3 were &gt;145–155 °C, &gt;290–300 °C, and &gt;190–230 °C, respectively. Large variation of salinities in each fluid inclusion assemblage suggests fluid mixing and dilution processes. Fluid inclusion gas compositions in the Stage 3 have weighted means of 98.98 mol% H2O, 0.75 mol% N2, 0.52 mol% CO2, 0.02 mol% CH4, 0.0021 mol% Ar, 0.0009 mol% H2S, and 0.00006 mol% He and indicate a signature of magmatic fluids mixed with meteoric waters or seawater. δ34SCDT values of sulfides in the stages 1, 2, and 3 in the prospect have three data clusters, (1) near 0 ‰ of chalcopyrite in the stages 1 and 2, (2) near −11 ‰ of bornite in the stage 2, and (3) +5 to +11 ‰ of the supergene chalcocite and covellite. Modes of occurrence of ores, fluid inclusions and sulfur isotope data show that the prospect is likely the same type as sediment‐hosted copper‐silver deposits with veining found in the Central African Copperbelt.

Effects of heavy metals on bacterial growth parameters in degradation of phenol by an Antarctic bacterial consortium.

Antarctica has often been perceived as a pristine continent until the recent few decades as pollutants have been observed accruing in the Antarctic environment. Irresponsible human activities such as accidental oil spills, waste incineration and sewage disposal are among the primary anthropogenic sources of heavy metal contaminants in Antarctica. Natural sources including animal excrement, volcanism and geological weathering also contribute to the increase of heavy metals in the ecosystem. A microbial growth model is presented for the growth of a bacterial cell consortium used in the biodegradation of phenol in media containing different metal ions, namely arsenic (As), cadmium (Cd), aluminium (Al), nickel (Ni), silver (Ag), lead (Pb) and cobalt (Co). Bacterial growth was inhibited by these ions in the rank order of Al < As < Co < Pb < Ni < Cd < Ag. Greatest bacterial growth occurred in 1 ppm Al achieving an OD600 of 0.985 and lowest in 1 ppm Ag with an OD600 of 0.090. At a concentration of 1.0 ppm, Ag had a considerable effect on the bacterial consortium, inhibiting the degradation of phenol, whereas this concentration of the other metal ions tested had no effect on degradation. The biokinetic growth model developed supports the suitability of the bacterial consortium for use in phenol degradation.

Sulfide Mineralization of Carbonate–Silicate Veins in Early Proterozoic Metabasites of North Karelia: Mineral Assemblages, Mineral Forms of Silver, and Fluid Inclusions

The work presents the first data on sulfide mineralization in carbonate–silicate veins, which are widespread on the islands and coast of the White Sea (North Karelia), associating with Early Proterozoic metamorphosed gabbroid bodies. The veins with Fe–Cu sulfide mineralization up to ore occurrences are localized within metabasite bodies and along their contacts with host gneisses. During the study of the mineral composition of the veins, the main assemblages of sulfide minerals were identified: chalcopyrite –bornite ± chlorite ± selenides and Pb–Ag tellurides (B1); digenite–bornite ± selenides and Pb, Ag, and Pd tellurides (B2); pyrite–bornite ± chalcopyrite (B3); marcasite–pyrite–bornite–chalcopyrite (B4); and siegenite–chalcopyrite ± acanthite ± chlorargyrite. The development of sulfide associations, as well as quartz–chlorite aggregates, was related to the late stage of vein formation. Inductively coupled plasma and laser ablation mass spectrometry analyses showed that bornite from association B1 has the highest silver content (up to 675 ppm) and, in terms of Ag, Se, and Bi contents, is closest to bornite from low-temperature epithermal, skarn, and high-temperature vein deposits. In general, bornite is the main Ag carrier in the studied associations, while digenite containing up to 1000 ppm Ag, as well as discrete silver minerals (selenides, tellurides, acanthite, and chlorargyrite), occur in subordinate quantities. Fluid inclusions in quartz from sulfide associations, as well as from a sulfide-free carbonate–silicate vein, were studied by cryo- and thermometric methods. It is established that mineralization at the late stages of vein formation was related to heterogeneous CO2–H2O–NaCl metamorphic fluid. Carbon dioxide fluid inclusions were captured by vein quartz at temperature of 253–314°C and pressure of 2 ± 1 kbar. Water–salt inclusions were captured in a wider temperature range of 100–500°С. The highest temperature fluid inclusions with temperatures of homogenization 300°С are characteristic of quartz veinlets of the siegenite–chalcopyrite association with Ag sulfide and chlorargyrite.

Myauchan Ore Field (Northeastern Asia), an Example of Weakly Eroded Ag–Pb–Zn Volcanoplutonic Mineralization

Abstract —The Myauchan ore field located in the Omsukchan zone of the Okhotsk–Chukotka Volcanic Belt is described. The Korennoe and Malyutka Ag–Pb–Zn ore occurrences forming this field are localized at the center of anticlinal fold of NW strike made up of Upper Triassic carbonate-terrigenous deposits intruded by stock-like bodies and dikes of Upper Cretaceous andesite, monzodiorite, granite-porphyry, and rhyolite-porphyry. Sulfide–carbonate–fluorite–quartz veins and vein–veinlet zones with arsenopyrite, pyrite, sphalerite, galena, chalcopyrite, and Ag-tetrahedrite are localized both in intrusions and in terrigenous strata. The field bears As–Sb–Ag–Pb–Au–Bi–Cu–Zn–W mineralization. Study of fluid inclusions and REE and ore element patterns show that the field ores formed from chloride solutions with the participation of surface waters in hydrothermal-magmatic system under epithermal conditions. The ores were deposited from solutions with TDS = 0.5–9.0 wt.% NaCl equiv. in the temperature range 106–287 ºC. The ores containing ca. 70 ppm Ag and up to 1.2% Pb formed through boiling-off of solutions enriched in iron salts. The ores with Ag &amp;lt; 7 ppm and Pb ≤ 25 ppm were generated from diluted hydrothermal solutions with predominant sodium salts and potassium admixture. Mineralization of the Myauchan ore field marks the upper level of the Ag–Pb–Zn ore system similar to the Gol’tsovoe deposit.

Detoxification role of amino acids and phytochelatins on two populations of harmel plant under silver stress.

Two non-metallicolous and metallicolous populations of harmel plants were compared regarding the role of proline, cysteine, reducing sugars, hydrogen peroxide (H2O2), glutathione, thiol compounds, organic acids, total free amino acids, and lipid peroxidation in detoxification and tolerance of silver stress (0, 1, 2.5, 5, 10 ppm Ag). The results of the present research state that the effects of Ag were increased total free amino acids, glutathione, organic acids, proline, reducing sugars, thiol compounds, and cysteine, so the accumulation of these compounds was higher in metallicolous populations than non-metallicolous. On the other hand, non-metallicolous populations showed higher content of lipid peroxidation and H2O2 than metallicolous populations under Ag stresses. Also, the accumulation of phytochelatins (PC) was observed with increasing Ag concentration, which shows that compared to glutathione, non-protein thiols have a higher concentration. The number of organic acids (malic acids, fumaric, oxalic, and citric) except acetic acid increased in the leaves of harmel in both populations. According to the results of this research, the harmel metallophilic population has a crucial role in the tolerance and detoxification of Ag stress, so the antioxidant responses of the plant against Ag stress in the non-metallicolous population were lower than the metallicolous population. Based on the above results, it can be concluded that the harmel plant has a detoxification mechanism to deal with high concentrations of Ag.

Genesis of copper mineralization in the polymetallic tin deposits from the Herberton Mineral Field, Queensland, Australia

The Herberton Mineral Field hosts multiple small-scale, polymetallic Sn-Cu and Sn-Zn deposits. The Baal Gammon and Isabel polymetallic deposits in the Herberton Mineral Field contain early Sn that is overprinted by sulfides. At Baal Gammon, the sulfide overprinting is Cu-In-rich, whereas Isabel is a Zn-Pb-In-rich system. These deposits are hosted in the meta-sedimentary rocks of the Hodgkinson Formation and the porphyry dikes and volcanic rocks of the Kennedy Igneous Association. Primary Sn in these deposits occurs as cassiterite, which was altered to stannite during sulfide mineralization. The sulfide ores from Baal Gammon consist of chalcopyrite, pyrrhotite, and minor sphalerite, and sphalerite, galena, and minor chalcopyrite are observed at Isabel. Chalcopyrite from Baal Gammon contains on average 609 ppm Ag, 1194 ppm In, and 1410 ppm Sn, whereas chalcopyrite from the Isabel deposit contains on average 2302 ppm Ag, 725 ppm In, and 1042 ppm Sn. Sulfur isotope (δ34S) measurements of in-situ chalcopyrite-pyrrhotite mineral pairs show limited variation and low values that are indicative of a magmatic sulfur source with limited interaction with sulfur from connate and meteoric fluids during mineralization. The chalcopyrite and pyrrhotite δ34S values at the Baal Gammon deposit vary between 0.99–1.91‰ and 1.35–2.48‰, respectively. The δ34S values at the Isabel deposit vary between 0.91–1.45‰ for chalcopyrite and 1.12–2.11‰ for pyrrhotite. The trace element composition of major sulfides and sulfur isotopes of chalcopyrite and pyrrhotite combined with thermodynamic modeling indicates that the mineralizing fluids at the Baal Gammon and Isabel deposits have an igneous source, where the metals were transported as metal-chloride complexes at low pH (< 5) and below ~ 300 °C. The source of these sulfide-rich mineralizing fluids is most likely derived from the magmatic activity associated with the emplacement of the Slaughter Yard Creek Volcanics during a period of crustal thinning between 300 and 280 Ma.

Leaf chlorophyll fluorescence and reflectance of oakleaf lettuce exposed to metal and metal(oid) oxide nanoparticles

BackgroundMost nanoparticles (NPs) have a significant impact on the structure and function of the plant photosynthetic apparatus. However, their spectrum of action varies significantly, from beneficial stimulation to toxicity, depending on the type of NPs, the concentration used and plant genotypic diversity. Photosynthetic performance can be assessed through chlorophyll a fluorescence (ChlF) measurements. These data allow to indirectly obtain detailed information about primary light reactions, thylakoid electron transport reactions, dark enzymatic stroma reactions, slow regulatory processes, processes at the pigment level. It makes possible, together with leaf reflectance performance, to evaluate photosynthesis sensitivity to stress stimuli. ResultsWe investigated effects of different metal and metal(oid) oxide nanoparticles on photosynthesis of oakleaf lettuce seedlings by monitoring the chlorophyll a fluorescence light radiation and reflectance from the leaves. Observations of ChlF parameters and changes in leaf morphology were carried out for 9 days in two-day intervals. Spectrophotometric studies were performed at 9th day. Suspensions of NPs with the following concentrations were used: 6% TiO2, SiO2; 3% CeO2, SnO2, Fe2O3; 0.004% (40 ppm) Ag; 0.002% (20 ppm) Au. Nanoparticles were applied directly on the leaves which caused small symptoms of chlorosis, necrosis and leaf veins deformation, but the plants fully recovered to the initial morphological state at 9th day. Leaf reflectance analysis showed an increase in FRI for SiO2-NPs and CeO2-NPs treatments and ARI2 for Fe2O3, however, WBI and PRI coefficients for the latter nanoparticle were lower than in control. Chlorophyll a fluorescence parameters have changed due to NPs treatment. Fe2O3-NPs caused an increase in Fv/F0, PIABS, ET0/RC, DI0/RC, ABS/RC in different time points in comparison to control, also Ag, Au and SnO2 treatment caused an increase in Fv/F0, PIABS or ET0/RC, respectively. On the other hand, TiO2-NPs caused a decrease in Fv/Fm and Fv/F0 parameters, but an increase in DI0/RC value was observed. SnO2-NPs decreased PIABS, but increased ET0/RC than compared to control. Nanoparticles affected the shape of the O-J-I-P curve in slight manner, however, further analyses showed unfavourable changes within the PSII antenna, manifested by a slowdown in the transport of electrons between the Chl molecules of the light-harvesting complex II and the active center of PSII due to NPs application.ConclusionChanges in ChlF parameters and leaf reflectance values clearly proved the significant influence of NPs on the functioning of the photosynthetic apparatus, especially right after NPs application. The nature of these changes was strictly depended on the type of nanoparticles and sometimes underwent very significant changes over time. The greatest changes in ChlF parameters were caused by Fe2O3 nanoparticles, followed by TiO2-NPs. After slight response of O-J-I-P curves to treatment of the plants with NPs the course of the light phase of photosynthesis stabilized and at 9th day were comparable to the control curve.

COMPARISON OF QUANTITATIVE METHODS FOR DETERMINING THE ANTIBACTERIAL EFFECTIVENESS OF NON-WOVEN TEXTILES

This contribution is aimed at comparing two quantitative methods for determining the antibacterial effectiveness of non-woven textiles and assessment of permanence of the antimicrobial finish of the nonwoven textile materials prepared from polypropylene fibers. Experience and results obtained by the quantitative test methods specified in AATCC TM 100 and STN EN ISO 20743 intended to evaluate the effectiveness of the antibacterial finish are published in the contribution. Emphasis is placed on comparability of the selected test methods, on the test microorganism used in the study as well as on evaluation of the results of antibacterial effectiveness. The non-woven fabrics, that were the subject of the evaluation, were pre-treated by surface activation with low-temperature plasma at atmospheric pressure and subsequently finished using antimicrobial (AMB) nanosol solution with a concentration of 15 ppm Ag+, 30 ppm Ag+, 60 ppm Ag+ and 120 ppm Ag+. Antibacterial effectiveness before washing and after 5 washing cycles is demonstrated on the specific examples obtained from practice.

THE INFLUENCE OF LOW-TEMPERATURE PLASMA ON PERMANENCE OF ANTIMICROBIAL NANO-FINISH

This paper describes the effect of low-temperature plasma on increasing permanence of surface finish of textile materials using an antimicrobial nanosol. Selected textile materials (polyester and polyamide woven fabrics, polypropylene non-woven fabric) were pre-treated by surface activation with low-temperature plasma at atmospheric pressure and subsequently finished using an antimicrobial (AMB) nanosol with a concentration of 60 ppm Ag+, 120 ppm Ag+ in the application solution. The goal was to increase the permanence of AMB nano-coating of textiles after washing and drying. To verify the effect of low-temperature plasma on increasing the permanence of the nanolayer, washing and drying was performed in accordance with the STN EN ISO 6330 standard. To determine antibacterial activity and effectiveness of the nano-coated textile materials, a quantitative test method was used in accordance with the technical standard AATCC TM 100. Evaluation of the antibacterial activity of the textile materials was performed before washing and after 20 washing cycles.

Effect of Ag Nanoparticles on Morphological and Physio-biochemical Traits of the Medicinal Plant Stevia Rebaudiana

Nowadays, overproduction of secondary metabolites in remedial herbs through giving biotic/abiotic stresses is an interesting area of research. In the current study, the influences of various concentrations of silver nanoparticles (Ag NPs) were evaluated on several morphological and physio-biochemical traits, such as the steviol glycosides level in Stevia. The findings showed that the herbs incubated with 400-ppm Ag NPs own the highest dry and fresh weight of shoot, while those incubated with 80- up to 200- ppm Ag NPs own the highest steviol glycosides content. As a result, we successfully improve the content of stevioside glycoside up to 1.75-fold by applying the 80- up to 200-ppm Ag NPs in Stevia medicinal plant. Moreover, our findings revealed that low concentrations the Ag NPs lead to an increase of glutathione content and total antioxidant capacity, and a decrease of MDA, whereas treatments at higher concentrations induced adverse effects for the plant. As a result, the treatment with Ag NPs low concentrations had a favorable efficacy on physio-biochemical and morphological characteristics of Stevia. These achievements are very promising, because they revealed a considerable capability for the Ag NPs application in enhancing the secondary metabolites in Stevia remedial herb. The present study is the first case assessing the desirable influences of Ag NPs on the Stevia, in regard with shifting of biosynthetic pathway of steviol glycosides in a concentration-dependent manner.

Karakteristik Mineralisasi Endapan Emas Epitermal Sulfidasi Rendah di Daerah Mekarbakti, Kecamatan Bungbulang, Kabupaten Garut, Provinsi Jawa Barat

The southern mountains of western Java have been known to have large gold deposit potential. The Mekarbakti area, located in Garut regency, is known to have gold-bearing quartz veins, but the distribution and characteristics of these veins are not well recorded. The purpose of this study is to determine the geological conditions of the deposits and the characteristics of the epithermal deposits in the study area, in term of alteration, ore mineralization, vein texture, and ore geochemistry. Field work includes random sampling of veins from surface outcrops and cores. Laboratory analysis includes mineragraphic, geochemical analysis by means of Fire Assay Atomic Absorption Spectrophotometry (FA-AAS) and Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) . The lithology of the Mekarbakti area is composed of volcanic rocks including andesite lava, andesite intrusion and pyroclastic rocks such as breccia and tuff. The mapping results show that the hydrothermal alteration that developed is divided into three zones of alteration type, namely the silicification zone (silica + - clay), the argillic zone (kaolinite + - smectite - illite) and the propylitic zone (chlorite - smectite - epidote - illite). Quartz texture is generally dominated by brecciated, colloform, comb, lattice bladed and cockade textures. The texture interpretation of the veins shows a crystalline quartz zone, which is enriched in base metals such as galena, sphalerite and chalcopyrite and a crustiform – colloform zone which usually contains gold and silver. Veins in the study area contain the elevated grades of 3.21 ppm Au and 75.5 ppm Ag.

Effect of SnO2 and Ag nano-additives on the performance, combustion and emission characteristics of diesel engine fueled with mango seed biodiesel

The emission from diesel engine leads to global warming and health issues. Alternative fuel is the better choice to solve the aforementioned issues. Bio-fuels have the potential to decrease the engine emission. This research works deals with the performance, combustion and emission characteristics of diesel engine operated with mango seed biodiesel blended with SnO2 and Ag particles. A test was conducted at different loading conditions on the single cylinder, four stroke, and vertical diesel engine. Three types of fuel blends were prepared viz. BD containing 25% methyl ester of mango seed oil and 75% diesel fuel, BD with 50 ppm Ag nanoparticles and BD with 50 ppm SnO2 nanoparticles. Experimental results were compared with the performance, combustion and emission results of diesel fuel. The BD–Ag biodiesel showed 4.4% higher BTE than the pure biodiesel due to the high thermal conductivity of Ag particles. Moreover, the BD–Ag biodiesel exhibited 16.7% more HRR than pure biodiesel owing to better heat transfer ability of Ag particles. In addition, the BD–Ag biodiesel displayed the maximum reduction in CO, UBHC and smoke density of 27.8%, 14.3%, and 11.8%, respectively, compared with that of diesel fuel.

BIOINSECTICIDE ACTIVITY OF SILVER NANOPARTICLES PRODUCT OF BIOSYNTHESIS USING ENTOMOPATHOGEN AGAINST THE BEET CATERPILLAR SPODOPTERA EXIGUA

Spodoptera exigua (Hubner) is a polyphagous insect pest that is detrimental to farmers. Nanotechnology exists as a renewable technology that can increase effectiveness due to the small size of particles it produces. This study aimed to determine the effectiveness of biosynthesis of silver nanoparticles from the fungi Metarhizium, Trichoderma, and The Bacillus bacteria which are biocontrol agents. The research started in February and ended in May 2020, at the Biological Research Laboratory, Faculty of Mathematics and Natural Sciences Education, University of Pendidikan Indonesia. The experiment was based on a completely randomized design method (CRD). Onion armyworm (Spodoptera exigua), two isolates from the fungi Metarhizium and Trichoderma were obtained from the Indonesia Vegetable Research Institute (IVERRI). Each extract of Metarhizium and Trichoderma fungi and 50 mL of extract from Bacillus bacteria were added to 50 mL of Ag + 60 ppm solution in a 250 mL glass tube. The mixture of Metarhizium mushroom extract with 60 ppm Ag + solution or Trichoderma mushroom with Ag + 60 ppm solution was incubated at 400 C with a rotation speed of 200 rpm for five days under a dark condition. For the mixture of bacterial extracts with Ag + 60 ppm solution, incubation was at room temperature with a rotation speed of 150 rpm for three days. Analysis of the effect of NPP on the mortality of S. exiguawas done using the treatments, Metarhizum, Trichoderma, Bacillus, NPP-Metarhizium, NPP-Trichoderma, NPP-Bacillus, NPP, and distilled water as controls. Third instar larvae of S. exigua were immersed for 30 seconds. After immersion, the larvae are placed in sterile Petri dishes that have been lined with sterile filter paper and provided with caterpillar feed. Observation of caterpillar mortality was recorded at 2, 4, 6, 9, 24, 48, 64, 72, 96 and 108 hours after treatment. There were three replicates the results showed that all the treatments caused death of the insect, both entomopathogens and entomopathogenic nanoparticles. We found the three treatments of silver nanoparticles highly lethal to S. exigua. Two treatments, NPP-Metarhizium and NPP-Bacillus even caused 100% mortality after 120 hrs treatment. The possible reason for the pathogenicity of these products is considered to be biosynthesis of nanoparticles and enzymatic substances

Implementation of Micro-EDM Monitoring System to Fabricate Antimicrobial Nanosilver Colloid.

This study implemented a discharge energy and success-rate monitoring system to replace the traditional oscillograph observation method and conducted a microbial control test for a nanosilver colloid prepared by an Electrical Discharge Machine (EDM). The advantage of this system is that the discharge conditions can be instantly and continuously observed, and the optimized discharge parameter settings can be recorded. The monitoring system can use the arcing rate to control the energy consumption of the electrodes to standardize the nanosilver colloid. The results show that the arcing rate, electrode weight loss, and absorption peak wavelength are very accurate. The nanosilver colloid prepared by EDM is free of any chemical additive, and in comparison to other preparation methods, it is more applicable to biotechnology, even to the human body. The microbial control test for the nanosilver colloid included a Bathroom sample, Penicillium, Aspergillus niger, and Aspergillus flavus. In test solution NO.1 (prepared by micro-EDM), the effects of all four samples were inhibited at 14mm in a metal ring experiment, and in the cotton pad experiment, Penicillium was inhibited at 17 mm. In the metal ring experiment, test solution NO. 2 (prepared by EDM) had an effect at 20 mm on the bathroom samples, but at only 15 mm on flavus. In the cotton pad experiment, the inhibited effect was more effective in Penicillium and Aspergillus Niger; both inhibited effects occurred at 25 mm. Test solutions NO.3 (prepared by micro-EDM) and NO.4 (32 ppm Ag+) had a 14–15 mm effect on all samples in the metal ring experiment. In the cotton pad experiment, NO.3 had an effect on Penicillium at 19 mm while the effect on the others occurred at 14 mm, and NO.4 had an effect at 25 mm in Penicillium and Aspergillus Niger, and only at 14 mm in the bathroom and Aspergillus flavus samples.

Targeted surface modification of Cu/Zn/Ag coatings and Ag/Cu particles based on sacrificial element selection by electrodeposition and redox replacement

The electrodeposition-redox replacement (EDRR) method was investigated for the preparation of two types of functional surfaces. A synthetic solution simulating Zn process solution containing 65 g/L Zn, 200 ppm Cu, 2 ppm Ag and 10 g/L H2SO4 was used as the source for creating functional surfaces EDRR experiments. The effects of operating parameters such as deposition potential (E1), deposition time (t1), and redox replacement time (t2) have been comprehensively studied. When E1 was selected to deposit Zn as the sacrificial metal, coherent Cu/Zn/Ag coatings with various chemical compositions, crystalline phases and surface morphology were obtained depending on the selected t1 and t2. The Cu/Zn/Ag coatings also exhibited competitive corrosion resistance (Ecorr = −683 to −634 mV vs. Hg/Hg2SO4, jcorr = 1.6–4.1 μA/cm2) when compared to those detailed in the literature. In contrast, when E1 was selected so that Cu was the sacrificial metal, separated Cu/Ag particles with controllable chemical composition, particle size (82–170 nm) and tunable surface plasmon resonance (SPR) behavior were formed through the variation of t1 and t2. In addition to the ability to tailor different functionalities for the surfaces from the same solutions, the process was performed in a single electrochemical cell without the addition of any complexing agents. Overall, these promising results demonstrated the versatility of the EDRR method to create various high value-added functional materials from complex hydrometallurgical solutions which contain multiple metal impurities.

The influence of Ag-Cu ions on natural biofilms of variable ages: Evaluation of MIC

In this study, the biofilms at different ages formed on galvanized steel coupons in a simulating cooling tower water system were exposed to the Ag-Cu ions over 504 h and the changes in the structure of the biofilms were investigated using electrochemical, microbiological, and surface analyses. The effect of the Ag-Cu ions on the structure of the natural biofilm during the maturation process was evaluated for the first time in this study. Exposure to Ag-Cu ions changed the structure of the biofilm, reducing the concentration of carbohydrates in EPS, causing the shedding from the biofilm by disrupting/making weakening the integrity of the biofilm. After exposure to Ag-Cu ions, the biofilm turned into a heterogeneous, fissured-porous and sandy structure. In addition, in the absence of the ions and after exposure to the ions, the MIC behavior of galvanized steel with natural biofilm at different ages was evaluated using electrochemical and gravimetric tests. It was determined that the galvanized steel suffered to MIC and exposure to Ag-Cu ions increased the corrosion rate of it. Therefore, using of Ag-Cu ions at maximum concentration values (0.1 ppm Ag and 1.3 ppm Cu) suggested by EPA is not recommended to prevent MIC problem in cooling tower systems.

Subacute toxic effects of silver nanoparticles oral administration and withdrawal on the structure and function of adult Albino Rats’ hepatic tissue

Products containing Silver nanoparticles (Ag NPs) are becoming vastly used in our daily life. The widespread increased introduction of Ag NPs in many aspects of life has raised researchers' concerns regarding their safety and toxicity for biological and environmental life in the past few years. The current study aimed to explore the subsequent effects of Ag NPs withdrawal, following short-term oral administration. Eighteen rats were assigned randomly into three groups (control group "1" and AG NPs treated groups "2" and "3"; 6 animals each). The control group received normal food and tap water while groups 2 & 3 received 0.5 ml of a solution containing 25 ppm Ag NPs for 14 days. Group 2 rats were sacrificed on day 14 whereas group 3 was left for another 14 days of particle cessation followed by euthanasia on day 28. Functional assessment was done by liver enzyme assays, hydrogen peroxide activity, hepatic Bdnf expression, and P53 immunoreactivity. Hepatic tissue structural assessment was done via hematoxylin and eosin, periodic acid-Schiff as well as Masson's trichrome stains. The results revealed a significant elevation of Hydrogen peroxide in group 2 only compared to the control group. Hepatic Bdnf and liver enzymes were both insignificantly affected. Structural abnormalities and enhanced apoptosis in hepatic tissue were found 14 days after ceasing the nanoparticles. In conclusion: Structural and functional insults following Ag NPs oral administration continues after particle withdrawal, and interestingly they do not necessitate apparent reflection on liver enzyme assays.