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An efficient, simple, robust strategy for the protection of copper in a neutral medium has been developed by the fabrication of electropolymerised film of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) + TiO2 composite. The electrosynthesised polymeric and composite films were characterised by different spectroscopic methods (FTIR, Raman spectroscopy, XPS, and XRD pattern). Electrochemical impedance spectroscopy and potentiodynamic polarisation studies confirmed the superior corrosion inhibition performance of fabricated composite film on copper in 3.5% NaCl medium. The enhanced protection efficiency of the polymeric composite could be due to the synergism between the organic polymer and inorganic particles. It is also found that the protection efficiency of the DMTD–TiO2 composite film lasts for more than 24 h. Further, SEM analysis reveals the formation of the protective film of the composite over Cu surface, while EDAX analysis unravels its composition. The study on effect of scan rate on electropolymerisation revealed that the electrodeposition of the polymer is a diffusion-controlled process. Thus, the study suggests that the fabrication of DMTD–TiO2 composite is an ideal strategy for the protection of copper in a neutral medium. [ABSTRACT FROM AUTHOR]

A simple and new strategy has been developed to protect metallic copper by forming composite material using graphene oxide (GO) and electropolymerised p-3-amino-5-mercapto-1,2,4-triazole (p-AMTa). The structure and the mechanism of the formation of the polymer and polymer composite were predicted from Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopic (XPS) analysis and Energy Dispersive X-ray (EDX) spectroscopy. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies (PDS) were employed to study the corrosion inhibitive action of p-AMTa + GO composite in 3.5% NaCl medium. The study revealed that, the copper electrode modified with the carbon based polymeric composite suppressed the anodic dissolution of copper thereby increasing its corrosion resistance. [ABSTRACT FROM AUTHOR]

In this work, 3-amino-5-mercapto-1,2,4-triazole (AMTa) was incorporated into 3-glycidoxypropyltrimethoxysilane (GPTMS)-based sol-gel coatings, which were self-assembled over a copper surface. The AMTa-doped GPTMS-based sol-gel coatings were characterized by Fourier transform infrared spectroscopy, Scanning Electron Microscopy, and Energy-Dispersive X-ray spectroscopy analyses. The protective ability of these coatings was evaluated by electrochemical impedance studies and potentiodynamic polarization measurements in 3.5 % NaCl medium. The AMTa-doped sol-gel coating showed enhanced corrosion protection ability compared to the un-doped GPTMS-based sol-gel coating, which may be largely due to the formation of thiolate bonds between copper and AMTa. The presence of a silane network through the amine group of AMTa could also be a reason for the enhanced protection. [ABSTRACT FROM AUTHOR]

Electropolymerization of 3-amino-5-mercapto-1,2,4-triazole (AMTA) on copper was carried out in methanol/NaOH solution by cyclic voltammetry. Chronoamperometry technique was used to investigate the formation kinetics of the polymer film. The effect of scan rate was also studied. Electropolymerized film of AMTA was duly characterized by Fourier transform infrared spectroscopy. Scanning electron microscopy was used to analyze the surface morphology of the polymer film. The protective ability of poly-3-amino-5-mercapto-1,2,4-triazole (p-AMTA) film was determined by electrochemical impedance spectroscopy and potentiodynamic polarization studies in NaCl medium. The results of the study showed that the p-AMTA film on copper afforded significant corrosion protection in neutral medium. Quantum theoretical studies revealed the adsorptive behavior of AMTA on copper. [ABSTRACT FROM AUTHOR]

The enhancement of protection of copper through pretreatment of metal surface with H2O2 and subsequent addition of H2O2 in the electrodeposition of 3-mercaptopropyltrimethoxysilane (MPTS) has been investigated in the present work. MPTS films over copper surface with and without H2O2 were investigated by FT-IR, XRD, Raman spectroscopy and SEM. The protection of copper surface by MPTS in the presence and absence of H2O2 in 1% NaCl medium was also investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies (PDS). The results of the study indicate that MPTS film electrodeposited on pretreated copper with 1000 ppm of H2O2 increases the inhibition efficiency to almost 100%. [ABSTRACT FROM AUTHOR]

The anticorrosion potential of Kappaphycus alvarezii on mild steel in both 1 M HCl and H2SO4 media has been studied using weight loss method at three different temperatures, electrochemical measurements, and surface analyses. The results revealed the inhibitive effect of K. alvarezii. The inhibition efficiency was found to increase with increasing concentration of the algal extract but decreased with increase in temperature which is attributed to the physisorption. The adsorption of the extract on the mild steel surface obeys the Temkin adsorption isotherm. Further, scanning electron microscope (SEM) and atomic force microscope (AFM) analyses supported the inhibitive action of this red alga by the formation of protective layer over the mild steel surface. [ABSTRACT FROM AUTHOR]

The corrosion inhibitive and adsorption behaviors of Hydroclathrus clathratus on mild steel in 1 M HCl and 1 M HSO solutions at 303, 313 and 323 K were investigated by weight loss, electrochemical, and surface analysis techniques. The results show that H. clathratus acts as an inhibitor of corrosion of mild steel in acid media. The inhibition efficiency was found to increase with increase in inhibitor concentration but to decrease with rise in temperature, suggestive of physical adsorption. The adsorption of the inhibitor onto the mild steel surface was found to follow the Temkin adsorption isotherm. The inhibition mechanism was further corroborated by the results obtained from electrochemical methods. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses supported the inhibitive action of the alga against acid corrosion of mild steel. [ABSTRACT FROM AUTHOR]

The essential oils obtained by hydrodistillation of leaves, stem and roots of Pleiospermium alatum were analyzed by Gas Chromatography and Gas Chromatography -- Mass Spectrometry. Thirty-one components comprising 97.3% of the leaf oil, twenty-nine components comprising 96.1% of the stem oil and twenty-three components comprising 95.0% of the root oil were identified. The major components in the leaf oil were elemol (12.5%) followed by pregeijerene (10.5%), α-cadinol (8.5%) and geijerene (8.5%). The stem oil contained elemol (12.4%), α-cadinol (11.1%) and epi-α-muurolol (9.4%) as the major components, while the root oil had α-cadinol (27.9%), α-bisabolol (11.5%), α-santalene (11.0%) and elemol (9.8 %) as the major components. [ABSTRACT FROM AUTHOR]

The corrosion inhibition potential of mild steel in 1M H2SO4 by Solanum nigrum extract was studied using weight loss method, potentiodynamic polarisation method, ac impedance studies and SEM technique. Weight loss measurements, carried out at three different temperatures, 303, 313 and 323 K, revealed the increase in inhibition efficiency with increasing concentration of the plant extract as well as the temperature of the system. Thus, the inhibitor exhibited the chemisorption mechanism following Temkin adsorption isotherm. Free energy of activation ΔG was also calculated so as to confirm the chemisorption process. Results of polarisation study revealed the mixed mode of inhibition. SEM studies supported the adsorption of inhibitor over the metal surface. The anticorrosion effect of S. nigrum is attributed to the presence of solasodine which was isolated and studied by theoretical, electrochemical and IR techniques. The possible adsorption mechanism of the inhibition is discussed vis-à-vis the presence of hetero atoms of solasodine. [ABSTRACT FROM AUTHOR]

Condensed tannins extracted from the seed testa of Anacardium occidentale is subjected to phytochemical and spectral studies such as UV and 13C NMR. Shell of Cocus nucifera on treatment with acid yields acid hydroxylates containing furfural which when condensed with tannins of A. occidentale form phenol–formaldehyde type resins. The spectral and physico-chemical properties of the resins are studied. Varnishes are prepared from these resins using linseed oil/linseed oil–tung oil. The service performances of the varnishes including their impedance spectra are evaluated. The results show that varnishes with good gloss and chemical resistivity can be prepared from these waste materials. [Copyright &y& Elsevier]

The present work involves the incorporation of dopamine (DA) into the hybrid sol-gel monolayers (Hy) consisting of (3-glycidoxypropyl)methyldiethoxysilane and Tetraethyl orthosilicate. The resultant doped hybrid layers coated over aluminum surface was characterized by FT-IR, UV-Vis, XRD, EDX and SEM analyses. The corrosion behavior of bare and coated aluminum substrates in 3.5 % NaCl medium was examined by cyclic voltammetry, potentiodynamic polarization and electrochemical impedance spectroscopy techniques. Results from the electrochemical measurements showed that the DA impregnated Hy sol-gel monolayers offered better corrosion protection with superior coating thickness than the Hy sol-gel monolayers without DA. The enhancement of protection could be attributed to the fact that DA promote the formation of strongly bonded and densely packed monolayer films, which show better adhesion than the conventional silane systems. [ABSTRACT FROM AUTHOR]

Copper metal and its alloys are the most used in the industries because it holds excellent conductivity and natural corrosion protectiveness against air/moisture. However, copper undergoes degradation in presence of aggressive 3.5% NaCl. Protective coating is one of the practical methods to safeguard copper metal. In this study, 2-amino-4-methyl-pyridine (AMP) was coated as self-assembled monolayer method (SAM) with different immersion periods (12 h/24 h) and investigated the corrosion potential against 3.5% NaCl medium. Chemical composition of AMP/SAM/Cu was characterized using Fourier-transform infrared (FT-IR) spectroscopy and morphological analysis using atomic force microscopy (AFM) techniques. AMP's corrosion inhibition potential were evaluated via electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDS) analyses. Quantum chemical calculations and molecular dynamics (MD) simulations explained the stronger adsorption of AMP over copper metal surface via self-assembly method. The corrosion analysis revealed that AMP's SAM formation (24 h immersion) enhances the corrosion protection of Cu metal, which is mainly due to the uniform thin adhesive compact layer formation and blocks incoming corrosive chloride ions. EIS investigation evident that AMP forms an adhesive layer over the copper surface and prevents the diffusion of aggressive corrosive medium, while PP studies revealed that AMP acts via the mixed mode of corrosion inhibition mechanism. AMP's significant inhibition efficiency 90% was confirmed via PP analysis. AFM analysis enabled the morphology image of AMP's shielding over Cu surface and the molecular modeling investigation supported well for the Cu–N (from AMP) bond formation. [ABSTRACT FROM AUTHOR]

The essential oil obtained by hydrodistillation of bark of Neolitsea foliosa var. caesia was analysed by Gas Chromatography and Gas Chromatography Mass Spectrometry. Thirty seven components constituting 81.6% of the bark oil was identified. The major constituents in the bark oil were α-cadinol (12.0%), elemol (9.0%) and α-muurolol (8.1%). The oil showed moderate activity against some of the tested Gram-positive and Gram-negative bacteria. [ABSTRACT FROM AUTHOR]

Three piperidin-4-one oxime derivatives viz. 3,5-dimethyl-2,6-diphenyl-piperidin-4-one oxime (DDPO), 3-ethyl-2,6-diphenyl-piperidin-4-one oxime (EDPO), and 1-methyl-3-isopropyl-2, 6-diphenyl-piperidin-4-one oxime (MIDPO) were synthesized. Corrosion inhibiting ability of these compounds in 1 M HCl was studied using weight loss study, potentiodynamic polarization measurements, electrochemical impedance spectroscopy, XRD and SEM with EDS measurements. Weight loss studies revealed that all the three oximes are good corrosion inhibitors. The order of inhibiting ability of these compounds is as follows: DDPO > EDPO > MINDO. Results of the polarization measurement showed that these inhibitors do not alter the mechanism of either hydrogen evolution or mild steel dissolution reaction, proving the mixed mode of inhibition. At constant acid concentration, increase of inhibitor concentration increased the charge transfer resistance (Rct), complimented with decrease of double layer capacitance (Cdl), thereby indicating the increase of percentage inhibition efficiency. XRD and SEM with EDS analysis provided strong proof for the existence of inhibitor film over the mild steel surface. [ABSTRACT FROM AUTHOR]

A systematic examination of the roots of Dalbergia congesta , yielded a new oligomeric isoflavonoid (1), a new tetramethoxy isoflavone (2) along with two known compounds, an isoflavone dalspinin (3) and a benzophenone, cearoin (4). On the basis of chemical and spectral evidences, compounds 1 and 2 were determined to be 5,7-dihydroxy-6,4′-dimethoxy-6′[2″-hydroxy-2″(2‴,5‴-dimethoxy neoflavonyl) ethenyl] isoflavone (dalcongestin) and 5,7-dihydroxy-2′,3′,5′,6′-tetramethoxy isoflavone, respectively. [ABSTRACT FROM AUTHOR]

This research introduces a novel fluorescence sensor ‘on-off-on’ employing nitrogen-doped carbon dots (N-CDs) with an ‘on-off-on’ mechanism for the selective and sensitive detection of Hg(II) and L-cysteine (L-Cys). N-CDs was synthesized using citric acid as the carbon precursor and urea as the nitrogen source in dimethylformamide (DMF) solvent, resulting in red emissive characteristics under UV light. Comprehensive spectroscopic analyses, including UV-Vis, fluorescence, FT-IR, XRD, XPS, Raman, and Zeta potential techniques, validated the structural and optical characteristics of the synthesized N-CDs. The maximum excitation and emission of N-CDs were observed at 548 and 622 nm, respectively. The quantum yield of N-CDs was calculated to be 16.1%. The fluorescence of N-CDs effectively quenches upon the addition of Hg(II) due to the strong coordination between Hg(II) and the surface functionalities of N-CDs. Conversely, upon the subsequent addition of L-Cys, the fluorescence of N-CDs was restored. This restoration can be attributed to the stronger affinity of the -SH group in L-Cys towards Hg(II) relative to the surface functionalities of N-CDs. This dual-mode response enabled the detection of Hg(II) and L-Cys with impressive detection limits of 15.1 nM and 8.0 nM, respectively. This sensor methodology effectively detects Hg(II) in lake water samples and L-Cys levels in human urine, with a recovery range between 99 and 101%. Furthermore, the N-CDs demonstrated excellent stability, high sensitivity, and selectivity, making them a promising fluorescence on-off-on probe for both environmental monitoring of Hg(II) and clinical diagnostics of L-Cys. [ABSTRACT FROM AUTHOR]

Bilirubin plays a significant role in human health management, particularly in the case of jaundice. Because of the need for the monitoring of bilirubin levels in jaundice patients, the development of a robust sensitive method becomes essential. Here, we describe the development of a highly sensitive and selective turn-off fluorometric detection method for bilirubin in blood serum samples using nitrogen-doped carbon dots (N-CDs). N-CDs was synthesized by the pyrolysis process, using citric acid and L-asparagine as the carbon and nitrogen sources, respectively. The prepared N-CDs solution showed highly intense blue emission with good stability. The HR-TEM image of N-CDs revealed spherical dot-like structures with an average size calculated to be 7.16 nm. Further, the surface functional groups of N-CDs were analyzed by FT-IR, Raman, XRD, and XPS techniques. Fluorescence spectra showed the maximum emission intensity at 443 nm (λex). The linear range of addition was performed from 1 to 150 µM, and the limit of detection (LOD) was determined to be 1.97 nM. The emission of N-CDs was quenched by Förster Resonance Energy Transfer (FRET) by adding bilirubin. These N-CDs showed extraordinary sensitivity and selectivity in the detection of bilirubin. Hence, this fluorescent probe has been proven successful in detecting the concentration of free bilirubin in human serum samples. [ABSTRACT FROM AUTHOR]

Highlights: [•] V2O5 were synthesized by low temperature chemical pyrophoric reaction method. [•] HR-SEM studies reveal the formation of V2O5 films consisting of nano-rods. [•] V2O5 used as potential applications for optoelectronics as well as solar cell applications. [ABSTRACT FROM AUTHOR]

Tribal populations of the Indian subcontinent have been of longstanding interest to anthropologists and human geneticists. To investigate the relationship of Indian tribes to Indian castes and continental populations, we analyzed 45 unlinked autosomal STR loci in 9 tribal groups, 8 castes, and 18 populations from Africa, Europe and East Asia. South Indian tribal populations demonstrate low within-population heterozygosity (range: 0.54 – 0.69), while tribal populations sampled further north and east have higher heterozygosity (range: 0.69 – 0.74). Genetic distance estimates show that tribal Indians are more closely related to caste Indians than to other major groups. Between-tribe differentiation is high and exceeds that for eight sub-Saharan African populations (4.8% vs. 3.7%). Telugu-speaking populations are less differentiated than non-Telugu speakers (FST: 0.029 vs. 0.079), but geographic distance was not predictive of genetic affinity between tribes. South Indian tribes show significant population structure, and individuals can be clustered statistically into groups that correspond with their tribal affiliation. These results are consistent with high levels of genetic drift and isolation in Indian tribal populations, particularly those of South India, and they imply that these populations may be potential candidates for linkage disequilibrium and association mapping. [ABSTRACT FROM AUTHOR]