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1.
We have studied the electrocatalytic activity of RuO2-PVC film electrodes, fabricated using RuO2 powders prepared at five different temperatures, viz., 300, 400, 500, 600 and 700°C, for the oxidation of glucose in high alkaline media, 1 to 3 M NaOH. The RuO2-PVC film electrodes have been first characterized in 1 to 3 M NaOH solution by cyclic voltammetry (CV) and rotating disc electrode (RDE) techniques in a wide potential range −1,100 to 450 mV (SCE), and three redox pairs representing Ru(IV)/Ru(III), Ru(VI)/Ru(IV) and Ru(VII)/Ru(VI) transitions have been identified. The voltammetric peaks at low sweep rates have been analyzed using surface activity theory formulated for interacting electroactive adsorption sites, and interaction terms have been evaluated. The total voltammetric surface charges have been analyzed as per Trassatti’s formalism with respect to their dependence on potential sweep rate, and charges associated with less accessible and more accessible surface sites have been calculated. For glucose oxidation, the results have indicated that RuO2 (700°C)-PVC electrode shows two oxidation peaks in contrast to RuO2 (300°C)-PVC electrode. Also, RuO2 (700°C)-PVC electrode exhibits higher intrinsic electrocatalytic activity than the 300°C electrode, although the former possesses lower electrochemically active surface area. Additionally, kinetic analyses made from RDE results with reference to Michealis–Menten (MM) enzyme catalysis has shown that RuO2 (700°C) electrode possesses extended glucose-sensing range in terms of MM kinetic constant, K
M
, compared to other electrodes. Possible reasons for such differences in the behavior of the electrodes of different temperatures towards glucose oxidation are identified from studies on oxidation of glucose in solutions of different pH, oxidation of different glucose derivatives, and also from physicochemical results from BET, XRD, SEM, DTGA, XPS analysis of RuO2 powder samples. 相似文献
2.
J. Shankara Narayanan C. Anjalidevi V. Dharuman 《Journal of Solid State Electrochemistry》2013,17(4):937-947
Development of nonenzymatic glucose sensors with high reproducibility and stability is an urgent need to reduce cost of regular diabetic monitoring. Here, we have fabricated ruthenium dioxide–poly(vinyl chloride)–Nafion (RuO2–PVC–Nafion) composite for direct glucose sensing in sodium hydroxide and phosphate buffer nonenzymatically for the first time. The restricted activity of the RuO2–PVC film electrode in alkaline pH is extended to neutral pH using Nafion as an outer membrane, which reduces the distance between Ru active sites by bridging effect and improves the electrode stability. The catalytic rate, measured in terms of change of RuO2 resistance, is similar irrespective of the medium for the high temperature annealed RuO2 (700 °C), whereas the low temperature annealed RuO2 (300 °C) is highly sensitive for the change in the pH of the solution. This is revealed by observing large Michaelis–Menten kinetic constant K M for the RuO2 (700 °C) than the low temperature annealed RuO2 (300 °C) due to effective increase in the catalytic active sites similar to oxygen evolution reaction. Contrast to this, the buffer solution does not influence significantly the apparent K M observed for RuO2 (300 °C) and has greater impact on the high temperature 500 and 700 °C annealed RuO2 samples. Cyclic voltammetry, chrono amperommetry, and electrochemical impedance spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction techniques are used for characterization of the sensor behavior. The RuO2–PVC–Nafion senses glucose selectively in the presence of potential interferences like fructose, galactose, mannose, sucrose, starch, uric acid, ascorbic acid, dopamine, and catechol in NaOH and phosphate buffer. Glucose sensing in the blood serum of the diabetic and nondiabetic patients is made. The results suggest that the RuO2–PVC–Nafion is a promising candidate for the development of nonenzymatic glucose sensors. 相似文献
3.
Arockiajawahar Anancia Grace Sukumar Thillaiarasi Venkataraman Dharuman 《Electroanalysis》2021,33(4):993-1006
Tungsten oxide (W) decorated titanium oxide (T) adsorbed onto a graphene (Gr) and modified the glassy carbon electrode for the electrochemical quantification of riboflavin (RF) in edible food and pharmaceuticals. For comparison, nanocomposites are formed using graphene oxide (GO), reduced graphene oxide (rGO) and pure graphite (G) sheets to study the electrochemical activities towards riboflavin. The ternary WTGr modified GCE shows the highest electrocatalytic activity due to synergetic interactions between the metal oxide and graphene. The electrochemical observations are supported by the SEM, HRTEM, XRD, UV-Vis, Zeta potential (ζ) and size data. The sensor shows a wide linear range 20 nM–2.5 μM with a detection limit 25.24 nM and sensitivity (4.249×10−8 A/nM). The fabricated sensor is validated in real samples. 相似文献
4.
The synthesis of (3S,4R,5R)-3-(2-hydroxyethyl)piperidine-3,4,5-triol 10 has been described from d-glucose. The base promoted cyclization for the construction of the piperdine framework is the key step of the synthesis. 相似文献
5.
BHOJRAJ Suresh 《色谱》2010,28(1):93-99
A novel in vitro dissolution profile was developed for formulated drug in combinational form containing naproxen sodium (NAP) and sumatriptan succinate (SUMA). This study was performed to understand the dissolution of the drug in the physiological temperature and pH. Dissolution testing was performed using USP 29 type II testing apparatus rotating at 50 r/min, in 900 mL deaerated buffer (pH 1.2, 4.5 and 6.8) which was maintained at (37±0.5) ℃. Quantification was performed using a developed and validated high performance liquid chromatographic (HPLC) method. Aceclofenac (ACE) was used as internal standard. SUMA, ACE and NAP were eluted at 4.8, 5.7 and 7.9 min, respectively. As expected for enteric coated immediate release (IR) tablets, the dissolution of NAP and SUMA was rapid and essentially complete within 2 h using phosphate buffer (pH 6.8). The comparison of the dissolution profiles was realized by model independent approach using a difference factor (f1), similarity factor (f2) and dissolution efficiency (DE). Statistical results showed the profiles were similar to the reference and the test products. Hence, this method demonstrated to be adequate for in vitro studies of NAP and SUMA in the combinational dosage form, since there is no official monograph, collaborating to the official codes. 相似文献
6.
Dharuman Chandrasekaran Yu-Lin Chiu Chun-Kai Yu Prof. Dr. Yung-Sheng Yen Prof. Dr. Yuan-Jay Chang 《化学:亚洲杂志》2021,16(22):3719-3728
In this paper, two D-π-D type compounds, C1 and C2 , containing dihydrodinaphthopentacene (DHDNP) as a π-bridge, p-methoxydiphenylamine and p-methoxytriphenylamine groups as the donor groups were synthesized. The four 4-hexylphenyl groups at the sp3-carbon bridges of DHDNP were acquainted with control morphology and improving solubility. The light absorption, energy level, thermal properties, and application as hole-transporting materials in perovskite solar cells of these compounds were fully investigated. The HOMO/LUMO levels and energy gaps of these DHDNP-based molecules are suitable for use as hole-transporting materials in PSCs. The best power conversion efficiencies of the PVSCs based on the C1 and C2 are 15.96% and 12.86%, respectively. The performance of C1 is comparable to that of the reference compound spiro-OMeTAD (16.38%). Compared with spiro-OMeTAD, the C1 -based PVSC device showed good stability, which was slightly decreased to 98.68% of its initial efficiency after 48 h and retained 81% of its original PCE after 334 h without encapsulation. These results reveal the potential usefulness of the DHDNP building block for further development of economical and highly efficient HTMs for PVSCs. 相似文献
7.
Two furan derivatives of cispentacin have been synthesized starting from a d-mannitol derived conjugated nitroolefin through intramolecular nitrile oxide cycloaddition (INOC) as a key step. 相似文献
8.
Suresh Dharuman Miranda J. Wallace Stephanie M. Reeve Jürgen B. Bulitta Richard E. Lee 《Molecules (Basel, Switzerland)》2022,27(5)
Infections due to Gram-negative bacteria are increasingly dangerous due to the spread of multi-drug resistant strains, emphasizing the urgent need for new antibiotics with alternative modes of action. We have previously identified a novel class of antibacterial agents, thioacetamide-triazoles, using an antifolate targeted screen and determined their mode of action which is dependent on activation by cysteine synthase A. Herein, we report a detailed examination of the anti-E. coli structure–activity relationship of the thioacetamide-triazoles. Analogs of the initial hit compounds were synthesized to study the contribution of the aryl, thioacetamide, and triazole sections. A clear structure–activity relationship was observed generating compounds with excellent inhibition values. Substitutions to the aryl ring were generally best tolerated, including the introduction of thiazole and pyridine heteroaryl systems. Substitutions to the central thioacetamide linker section were more nuanced; the introduction of a methyl branch to the thioacetamide linker substantially decreased antibacterial activity, but the isomeric propionamide and N-benzamide systems retained activity. Changes to the triazole portion of the molecule dramatically decreased the antibacterial activity, further indicating that 1,2,3-triazole is critical for potency. From these studies, we have identified new lead compounds with desirable in-vitro ADME properties and in-vivo pharmacokinetic properties. 相似文献
9.
Dr. Joghee R. Suresh Dr. Glenn Whitener Gabriele Theumer Dr. Dirk J. Bröcher Dr. Ingmar Bauer Prof. Dr. Werner Massa Prof. Dr. Hans-Joachim Knölker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(60):13759-13765
Dibenzo[cde,opq]rubicene has been synthesized by an eight-step reaction sequence including an iron-mediated [2+2+1] cycloaddition and a flash vacuum pyrolysis as key steps. Two crystal modifications of the S-shaped, planar polycyclic aromatic hydrocarbon have been obtained and characterized by X-ray diffractometry. 相似文献
10.
Determination of the Influence of Side‐Chain Conformation on Glycosylation Selectivity using Conformationally Restricted Donors
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Dr. Suresh Dharuman Prof. Dr. David Crich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4535-4542
The synthesis of a series of conformationally locked mannopyranosyl thioglycosides in which the C6?O6 bond adopts either the gauche,gauche, gauche,trans, or trans,gauche conformation is described, and their influence on glycosylation stereoselectivity investigated. Two 4,6‐O‐benzylidene‐protected mannosyl thioglycosides carrying axial or equatorial methyl groups at the 6‐position were also synthesized and the selectivity of their glycosylation reactions studied to enable a distinction to be made between steric and stereoelectronic effects. The presence of an axial methoxy group at C6 in the bicyclic donor results in a decreased preference for formation of the β‐mannoside, whereas an axial methyl group has little effect on selectivity. The result is rationalized in terms of through‐space stabilization of a transient intermediate oxocarbenium ion by the axial methoxy group resulting in a higher degree of SN1‐like character in the glycosylation reaction. Comparisons are made with literature examples and exceptions are discussed in terms of pervading steric effects layered on top of the basic stereoelectronic effect. 相似文献