Photo-oxidative Decolorization of Brilliant Blue with AgNPs as an Activator in the Presence of K2S2O8 and NaBH4.

The decolorization of brilliant blue (E133) in aqueous solution by K2S2O8 and NaBH4 with AgNPs as an activator was studied spectrophotometrically under normal laboratory conditions. Batch experiments were performed to investigate the effects of reaction time, initial dye concentration, activator concentration, solution pH, and temperature on the decolorization of E133. K2S2O8 and NaBH4 did not decolorize the dye E133 in the absence of AgNPs. The optimum dosage of AgNPs was 0.01 g/L, and 98% dye E133 degradation was observed with 3.75 mM K2S2O8 at 30 °C in ca. 60 min of reaction time. In the NaBH4/AgNPs system, only 60% dye degradation was observed for an identical reaction condition. The decolorization rate constant increases with the increase in concentrations of AgNPs, K2S2O8, NaBH4, and reaction temperature. The decolorization degree of the E133 responded linearly with K2S2O8 and NaBH4 concentrations. The existence of sulfate radicals (SO4 · -) and hydroxyl radicals (HO·) generated during the decolorization of E133 was identified by using ethanol and tertiary butyl alcohol as scavengers. Based on the E133 solution absorbance changes at 628 nm, the decolorization mechanism was proposed and discussed.

Chitosan capped noble metal doped CeO2 nanomaterial: Synthesis, and their enhanced catalytic activities.

Chitosan (Ch) capped Ch-CeO2, Ch-CeO2/Ag, Ch-CeO2/Pd and Ch-CeO2/Ag/Pd nanomaterials were fabricated using seedless and metal displacement plating method. The Ce4+ ions first formed complex with Ch through amino and hydroxyl groups and then reduced in presence of NaOH and molecular oxygen at higher temperature. Ch-Ag+ and Ch-Pd2+ complexes adsorbed on the surface of Ch-CeO2 and reduced under potential deposition. Ninhydrin reaction test was conducted to confirm the presence of chitosan on the surface of NMs. The catalytic efficiency was increases markedly with incorporating noble metal into Ch-CeO2 NMs. Ch-CeO2/Ag/Pd exhibits higher catalytic performance towards hydrogen generation due to the narrow band gap (2.65 eV) and smaller work function of CeO2 (ϕ = 2.8 eV) than that of Ag0(ϕ =4.6 eV) and Pd0 (ϕ = 5.2 eV). Hydrogen generation rates increases with temperature and activation energies were found to be 63.2, 60.3, 56.2 and 53.0 kJ/mol for Ch-CeO2, Ch-CeO2/Ag, Ch-CeO2/Pd, and Ch-CeO2/Ag/Pd, respectively. CeO2/Ag/Pd shows better catalytic efficiency due to the strong interaction between Ag/Pd metal and active support CeO2. The photocatalytic rates drastically inhibited with scavengers, demonstrate that the reactive radical oxygen species (HO and O2-), holes (h+) and electrons (e-) played major role in the NaBH4 hydrolysis.

Sennoside A drug capped biogenic fabrication of silver nanoparticles and their antibacterial and antifungal activities.

Sennoside A (dianthrone glycoside) shows laxative properties and used as a folk traditional medicine. Sennoside A capped silver nanoparticles (Ag/sennoside A) were synthesized at room temperature for the first time by using sennoside A as reducing and capping agent. UV-visible spectroscopic data reveals that the absorption peaks of pure sennoside A was appeared at 266, and 340 nm, which red shifted to 304, and 354 nm at higher sennoside A concentration. Upon addition of the Ag+ ions, an additional peak also observed at 398 nm, indicating the formation of spherical sennoside A capped silver nanoparticles (Ag/sennoside A). Cetyltrimethylammonium bromide (CTAB) was used a stabilizing agent to determine the role of cationic micelles on the nucleation and growth processes of Ag/sennoside A NPs formation. The 2,2-diphenyl-1-picrylhydrazyl nitrogen radical (DPPH · ), two bacteria strains (Staphylococcus aureus and Escherichia coli) and two yeast strains (Candida albicans ATCC 10231 and Candida parapsilosis ATCC 22019) were used to determine the antioxidant and antimicrobial properties of Ag/sennoside A NPs. In addition, Rhein-9-anthrone (4,5-dihydroxy-10-oxo-9H-anthracene-2-carboxylate) was isolated from the acidic hydrolysis of glycoside linkage of sennoside A and characterized. The antioxidant and antimicrobial activities of rhein-9-anthrone were also determined against DPPH radical, antibacterial and antifungal strains. The minimum inhibitory concentration was determined and discussed.

Betanin assisted synthesis of betanin@silver nanoparticles and their enhanced adsorption and biological activities.

Natural red purple dye, Betanin, was extracted from the beetroot, purified by aqueous two- phase extraction and gel permeation column chromatography, and used as a reducing agent for the synthesis of silver-betanin core-shell triangular nanodisks for the first time. Spectroscopic data show that the nanoparticle structure is core@shell like with Ag as core and betanin as shell. Langmuir monolayer model (qm = 32.4 mg/g, RL = 0.99 and R2 = 0.997) was the best fit adsorption isotherm for the dye removal. Adsorption kinetics is well explained by pseudo-second-order equation. Gibbs free energy (ΔG0 = -2.59 kJ mol-1), enthalpy (ΔH0 = 18.05 kJ mol-1), and entropy (ΔS0 = 68.92 J/K/mol) were calculated and discussed. The antibacterial activity of betanin-AgNPs were determined against Escherichia coli MTCC-450 (E. coli) and Staphylococcus aureus MTCC-3160 (S. aureus) bacteria.

Eco-friendly walnut shell powder based facile fabrication of biogenic Ag-nanodisks, and their interaction with bovine serum albumin.

Walnut shell biomass was used for the extraction of juglone by water as a solvent at room temperature. Upon addition of AgNO3 to a dye solution, prefect transparent pale brown color develops within the reaction time. UV-visible spectroscopy revealed the appearance of surface plasmon absorption (SRP) peak at 410 nm for spherical silver nanoparticles (AgNPs). Transmission electron microscopy suggested the formation of spherical and truncated triangular nano-plate geometry of AgNPs with average diameter 25 nm. Juglone-surfactant interactions (micellization and incorporation) have been studied spectrophotometrically by using cationic cetyltrimethylammonium bromide (CTAB). The presence of CTAB has significant impacts on size, shape and the size distribution of AgNPs. The nucleation, growth, and adsorption processes depend on the [CTAB]. It also catalyzes the Ag+ ions reduction by juglone with a rate enhancement of ca. 100-fold. Activation parameters (activation energy, enthalpy of activation and entropy of activation) were evaluated to the synthesis of silver nano-disks. Antioxidant activity of juglone was accessed by the scavenging effect on DPPH radical. Silver nanoparticles was also used as quencher to determine their interaction with bovine serum albumin (BSA). The quenching constant were found to be 1.4 × 103 M-1 L s-1 and 4.8 × 103 M-1 L s-1 for two BSA concentrations.

Central Odontogenic Fibroma: A Case Report.

A central odontogenic fibroma (COF) is a rare tumor of odontogenic origin with a diverse histopathology found in both the mandible and the maxilla. It can often be difficult to diagnose; therefore, it is necessary to evaluate the clinical, radiographic, and histopathological analyses of COF and co-relate them in a manner to make definitive diagnosis easier for the treating physician. Herein, we report and discuss the first known case of central odontogenic fibroma in Pakistan: a 16-year-old boy presenting as a hard bony painless swelling of the left mandibular region. It appeared as a large, well-defined unilocular radiolucency on the orthopantomogram, making it indistinguishable from other radiolucent tumors of the mandible. Histologically, the lesion consisted of nests of odontogenic epithelium in between the fibroblastic stroma, confirming a definitive diagnosis of COF. It was treated by conservative surgical excision followed by curettage and no postoperative complications were reported.

Eco-friendly green synthesis of Ag@Fe bimetallic nanoparticles: Antioxidant, antimicrobial and photocatalytic degradation of bromothymol blue.

Silver-iron bimetallic nanoparticles (BMNPs) were synthesized by using AgNO3 and Fe(NO3)3 as an Ag/Fe source in presence of Palm dates fruit. Upon addition of extract to a solution of Ag+ and Fe3+, a prefect transparent stable dark brown color appears with in a few minuets at room temperature. In order to conform the nature of resulting color, UV-visible spectroscopy, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) techniques were used. The absence of surface plasmon resonance (SPR) peaks in the entire UV-visible region suggests the formation of silvercore-ironshell BMNPs. The obtained nanoparticles were used as a catalyst for the degradation of bromothymol blue (BTB) in absence and presence of sunlight. The degradation kinetics was studied in presence of electron acceptors and scavengers, such as hydrogen peroxide, ammonium oxalate, ammonium per sulphate, benzoquinone, isopropyl alcohol, n-butanol, potassium bromate and potassium iodide. Radical trapping experiments demonstrates that active holes (h+) and generated hydroxy radical are primary species involved in H2O2 assisted catalytic degradation process. The free-radical scavenging, antioxidant and antimicrobial activities were determined for extract and BMNPs. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activities were found to increase with increasing the amounts of extract. The silver-iron showed good invitro antibacterial activities against human pathogens.

Biogenic synthesis, optical, catalytic, and in vitro antimicrobial potential of Ag-nanoparticles prepared using Palm date fruit extract.

Silver nanoparticles (AgNPs) have been synthesized via green route using an aqueous extract of Palm date fruit pericarp extract. The appearance of the yellow color and the surface resonance plasmon (SRP) band at around 400-450nm in UV-Visible spectroscopy initially reveals the formation of AgNPs. The particle size, crystalline nature, and size distribution was confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) ring patterns, energy dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS) techniques. The particles size ranged ca. 3nm to 30nm and are spherical in shape. The microbial activity of biogenic AgNPs was tested on clinical multiple drug resistance Staphylococcus aureus, Escherichia coli and Candida albicans reference strain. Zones of inhibition growth increases with [AgNPs]. The results suggest that the particle tested in this study certainly mediate the inhibition of bacterial and fungus growth. To overcome the serious problems related to environment like discharge of hazardous chemicals to water bodies, AgNPs have been found to be very important in the catalytic degradation of 4-nitrophenol. The rate of degradation strongly depends on the sun light exposure. Based on the chemical and kinetic studies, an attempt has been made to elucidate the mechanism of AgNPs formation.

Seedless synthesis of nanocomposites, optical properties, and effects of additives on their surface resonance plasmon bands.

The work describes an easy seedless competitive chemical reduction method for the synthesis of Ag@Au/Ag bimetallic nanoparticles by mixing AgNO3, HAuCl4 and cysteine. Transmission electron microscope (TEM) images show that the large number of irregular, cross-linking, and aggregated Ag@Au/Ag are formed in a reaction mixture (HAuCl4+AgNO3+cysteine), whereas flower-like nanocomposites are obtained in presence of cetyltrimethylammonium bromide (CTAB), which acted as a shape-directing agent. Optical images reveal that the initially reaction proceeds through formation of purple color, which changes into dark brown color with the reaction time, indicating the formation of Ag@Au/Ag nanocomposites. The Ag+ has strong tendency to form complex with cysteine. Firstly, the reduction of Ag+ ions to Ag0 occurred by the HS group of the cysteine-Ag complex. Secondly, AuCl4- ions adsorbed on the positive surface of Ag0, which undergoes reduction by potential deposition, and leads to the formation of Ag@Au/Ag bimetallic nanoparticles. Inorganic electrolytes (NaCl, NaBr, NaNO3 and Na2SO4) have significant impact on the stability and aggregation of Ag@Au/Ag nanocomposites.

Growth of Ag-nanoparticles in an aqueous solution and their antimicrobial activities against Gram positive, Gram negative bacterial strains and Candida fungus.

Silver nanoparticles (AgNPs) were synthesized using Ocimum sanctum (Tulsi) leaves aqueous extract as reducing as well as a capping agent in absence and presence of cetyltrimethylammonium bromide (CTAB). The resulting nanomaterials were characterized by UV-visible spectrophotometer, and transmission electron microscope. The UV-Vis spectroscopy revealed the formation of AgNPs at 400-450 nm. TEM photographs indicate that the truncated triangular silver nanoplates and/or spherical morphology of the AgNPs with an average diameter of 25 nm have been distorted markedly in presence of CTAB. The AgNPs were almost mono disperse in nature. Antimicrobial activities of AgNPs were determined by using two bacteria (Gram positive Staphylococcus aureus MTCC-3160), Gram negative Escherichia coli MTCC-450) and one species of Candida fungus (Candida albicans ATCC 90030) with Kirby-Bauer or disc diffusion method. The zone of inhibition seems extremely good showing a relatively large zone of inhibition in both Staphylococcus aureus, Escherichia coli, and Candida albicans strains.

Bio-conjugated silver nanoparticles: from Ocimum sanctum and role of cetyltrimethyl ammonium bromide.

In this paper we have reported the spectrophotometeric and transmission electron microscopic (TEM) data to the shape-directing role of cetyltrimethylammonium bromide (CTAB) on the green extra-cellular synthesis of bio-conjugated Ag-nanoparticles using Ocimum sanctum leaves extract. TEM images revealed that the nanoparticles are mostly spherical (average particle size ranged from 18 to 35nm) with some truncated triangular nanoplates, aggregated in a beautiful manner to yield locket-like silver and capped by a thin layer of biomolecules of O. sanctum, whereas nanoparticles are highly poly-dispersed in presence of CTAB. The shape and position of wavelength maxima strongly depends on the reaction time, [leaves extract] and [CTAB]. The visual observations also suggest that the prefect transparent silver sol becomes turbid in presence of CTAB after some time.

Silver nanoparticles formation using tyrosine in presence cetyltrimethylammonium bromide.

Upon addition of silver nitrate (precursor) to a solution of tyrosine (reductant) and cetlytrimethylammonium bromide (stabilizer), a transient species appears as the reaction time increases, which is stable for several months. The formation of silver nanoparticle was observed visually by color change (pale yellow to brownish yellow). In order to confirm the nature of the transient species, spectroscopic, kinetic, coagulation, transmission and scanning electron microscopic experiments were carried out. The reaction follows first-order kinetics with respect to [tyrosine] and [Ag(+)] under our experimental conditions. The phenolic -OH group of tyrosine is responsible for the reduction of Ag(+) ions. On the basis of various observations, the most plausible mechanism is proposed and discussed.

Silver nanoparticles to self-assembled films: green synthesis and characterization.

In the present paper silver nanoparticle was synthesized by chemical reduction of silver nitrate by oxalic acid in aqueous solution. The nanoparticle film (self-assembled; mirror like illumination) on the wall of the clean glass surface was also observed after some days. The synthesized silver particles show an intense surface resonance plasmon band in the visible region at 425 nm. Transmission electron microscopy, selected areas electron diffraction, and UV-visible spectroscopy have been employed to characterize Ag-nanoparticles. The nanoparticle films were also observed using conventional visual and scanning electron microscope (spherical particles and size ranging from 23 to 245 nm). The transmission electron micrograph revealed that the average size of silver nanoparticle were ≤10 nm and 21-60 nm, respectively.

Preparation of silver nanoparticles using tryptophan and its formation mechanism.

A non-toxic route was used for the preparation of silver nanoparticles using tryptophan (Trp) as reducing/stabilizing agent in the presence of cetyltrimethyl ammonium bromide (CTAB). Role of water soluble neutral polymer poly(vinylpyrrolidone) (PVP) has been studied on the growth of yellow colour silver nanoparticle formation. The synthesized nanostructures were characterized by UV-Visible absorption spectroscopy, transmission electron microscopy (TEM) by observing the size and distribution of silver nanoparticles. As the reaction proceeded, particles grew up to about 10 and 20 nm in the presence and absence of PVP, respectively, as determined by TEM. The formed nanoparticles showed the highest absorption plasmon band at 425 nm. Rate of silver sol formation increases with the [Trp], [CTAB] and [PVP], reaching a limiting value and then decreases with the increase in concentrations of these reagents. It was observed that nanoparticles are spherical, aggregated and poly dispersed in the absence and presence of PVP, respectively. On the basis of kinetic data, a suitable mechanism is proposed and discussed for the silver sol formation.

Sub- and post-micellar catalytic and inhibitory effects of cetyltrimethylammonium bromide in the permanganate oxidation of phenylalanine.

The kinetics of phenylalanine (phe) oxidation by permanganate has been investigated in absence and presence of cetyltrimethylammonium bromide (CTAB) using conventional spectrophotometric technique. The rate shows first- and fractional-order dependence on [MnO(4)(-)] and [phe] in presence of CTAB. At lower values of [CTAB] (< or =10.0x10(-4)moldm(-3)), the catalytic ability of CTAB aggregates are strong. In contrast, at higher values of [CTAB] (> or =10.0x10(-4)moldm(-3)), the inhibitory effect was observed in absence of H(2)SO(4). We find that anions (Br(-), Cl(-) and NO(3)(-)) in the form of sodium salts are strong inhibitors for the CTAB catalyzed oxidation. Kinetic and spectrophotometric evidences for the formation of an intermediate complex and an ion-pair complex between phe and MnO(4)(-), CTAB and MnO(4)(-), respectively, are presented. A mechanism consistent with kinetic results has been discussed. Complex formation constant (K(c)) and micellar binding constant (K(s)) were calculated at 30 degrees C and found to be K(c)=319mol(-1)dm(-3) and K(s)=1127mol(-1)dm(-3), respectively.