pH-dependent size and structural transition in P123 micelle induced gold nanoparticles

RSC Advances ◽  
2015 ◽  
Vol 5 (85) ◽  
pp. 69765-69775 ◽  
Author(s):  
P. Chatterjee ◽  
S. Hazra
Keyword(s):  
Gold Nanoparticles ◽  
Structural Transition ◽  
Ph Value ◽  
Ph Dependent

The transition of the structure and size of AuNPs at a pH value around 9.5, from slowly grown, well-faceted, large (≫19 nm), less uniform and near connected to fast grown, near symmetrical, small (<19 nm), more uniform and well-separated, is observed.

Molecularly Imprinted Sensor for Ascorbic Acid Based on Gold Nanoparticles and Multiwalled Carbon Nanotubes

2020 ◽  
Vol 16 (7) ◽  
pp. 905-913
Author(s):  
Youyuan Peng ◽  
Qingshan Miao
Keyword(s):  
Carbon Nanotubes ◽  
Gold Nanoparticles ◽  
Ascorbic Acid ◽  
Multiwalled Carbon Nanotubes ◽  
Ph Value ◽  
Biological Fluids ◽  
Water Soluble ◽  
Multiwalled Carbon ◽  
Experimental Conditions ◽  
Molecularly Imprinted

Background: L-Ascorbic acid (AA) is a kind of water soluble vitamin, which is mainly present in fruits, vegetables and biological fluids. As a low cost antioxidant and effective scavenger of free radicals, AA may help to prevent diseases such as cancer and Parkinson’s disease. Owing to its role in the biological metabolism, AA has also been utilized for the therapy of mental illness, common cold and for improving the immunity. Therefore, it is very necessary and urgent to develop a simple, rapid and selective strategy for the detection of AA in various samples. Methods: The molecularly imprinted poly(o-phenylenediamine) (PoPD) film was prepared for the analysis of L-ascorbic acid (AA) on gold nanoparticles (AuNPs) - multiwalled carbon nanotubes (MWCNTs) modified glass carbon electrode (GCE) by electropolymerization of o-phenylenediamine (oPD) and AA. Experimental parameters including pH value of running buffer and scan rates were optimized. Scanning electron microscope (SEM), fourier-transform infrared (FTIR) spectra, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were utilized for the characterization of the imprinted polymer film. Results: Under the selected experimental conditions, the DPV peak currents of AA exhibit two distinct linear responses ranging from 0.01 to 2 μmol L-1 and 2 to 100 μmol L-1 towards the concentrations of AA, and the detection limit was 2 nmol L-1 (S/N=3). Conclusion: The proposed electrochemical sensor possesses excellent selectivity for AA, along with good reproducibility and stability. The results obtained from the analysis of AA in real samples demonstrated the applicability of the proposed sensor to practical analysis.

scholarly journals A pH-dependent structural transition in the homopurine-homopyrimidine tract in superhelical DNA

1986 ◽  
Vol 2 (3) ◽  
pp. 115-124 ◽  
Author(s):  
V. I. Lyamichev ◽  
S. M. Mirkin ◽  
M. D. Frank-Kamenetskii
Keyword(s):  
Structural Transition ◽  
Ph Dependent

Temperature and pH-dependent swelling and copper(ii) adsorption of poly(N-isopropylacrylamide) copolymer hydrogel

RSC Advances ◽  
2015 ◽  
Vol 5 (76) ◽  
pp. 62091-62100 ◽  
Author(s):  
Jinjin Cheng ◽  
Guorong Shan ◽  
Pengju Pan
Keyword(s):  
Free Radical ◽  
Radical Polymerization ◽  
Maleic Acid ◽  
Adsorption Process ◽  
Ph Value ◽  
Free Radical Polymerization ◽  
Stimuli Responsive ◽  
Copolymer Hydrogel ◽  
Ph Dependent

Poly(N-isopropylacrylamide-co-acrylamide-co-maleic acid) (PNIPAM-AM-MA) hydrogel, which can make the Cu2+ adsorption process stimuli-responsive under temperature and pH value control, has been synthesized by free radical polymerization.

Photodegradation of Cationic and Anioic Dyes by pH-Dependent Dispersion of Amphoteric g-C3N4 Nanosheets

2020 ◽  
Vol 20 (10) ◽  
pp. 6215-6221
Author(s):  
Qingmei Zhang ◽  
Aoli Wen ◽  
Guoliang Chen ◽  
Juan Huang ◽  
Xu Zhou ◽  
...  
Keyword(s):  
Ph Value ◽  
Cationic Dye ◽  
Amino Groups ◽  
Anionic Dye ◽  
Chromotrope 2R ◽  
Different Types ◽  
Acidic Conditions ◽  
Ph Dependent

g-C3N4 nanosheets (NSs) were prepared via H2SO4 exfoliation from the bulky g-C3N4 and the photocatalytic (PC) activities were investigated comprehensively using Rodamine B (RhB) and Chromotrope 2R (Ch2R) as candidate pollutants. The results showed that the pH value have important functions in the improvement of photodegradation performance of C3N4 NSs. RhB as cationic dye could be photodegraded more efficiently under acidic conditions while Ch2R as anionic dye was degraded easily in pH ≥ 11 solution. In particular, the Ch2R could be degraded completely within only 30 min in pH = 11 solution. It might be because the amphoteric C3N4 NSs surface with carboxyl and amino groups possessed negative and positive charges in alkaline and acidic conditions, respectively. These results presumably provided a new idea to enhance the pH-dependent photodegradation activity and degrade different types of pollutants selectively by adjusting the pH of amphoteric nanocatalyts.

Study on the Radiosensitizing Applications of Gold Nanoparticles

2016 ◽  
Vol 851 ◽  
pp. 26-30 ◽  
Author(s):  
Chang Shu Tsai ◽  
Jou Kang Hsiao
Keyword(s):  
Gold Nanoparticles ◽  
Ph Value ◽  
Trisodium Citrate ◽  
Molar Ratio ◽  
Human Breast ◽  
X Ray ◽  
Vis Spectroscopy ◽  
M Phase ◽  
Redox Method ◽  
20 Nm

Citrate-coated gold nanoparticles (AuNPs) were prepared by using redox method and its characterization was studied thoroughly. In the preparation process, the varieties of factors were examined by TEM morphology, DLS zetasizer, XPS analysis and UV-Vis spectroscopy for evaluating their qualities and stability. The experimental results obtained under optimal condition, which are 100±5°C of reaction temperature, 4.5-6.4 of the pH value, 2-10 of molar ratio between trisodium citrate and tetrachloroauric acid, respectively. The fluorescent intensities of DCFDA-stain indicate the amount of generated ROS (reactive oxygen species) by AuNPs. The cell cycle for MDA-MB-231 human breast cancer cells exhibits S-phase arrest which can prevent mitosis. The radiosensitizing effect of AuNPs with 20 nm diameter in MDA-MB-231 was investigated by RCGG values (ratio of cell numbers in the G2/M phase to the G0/G1 phase, RCGG) and its radiosensitizing efficiency was ca. 2.29 to 3.75 fold. In this study, it was found that the radiosensitizing efficiency is related to the cytotoxicity by AuNPs. After the irradiation by x-ray to cells, the enhancement value in the presence of 20 nm diameter AuNPs were 17.2% for 3 Gy and 18.9% for 7 Gy respectively. Compared to the irradiated group alone, the enhancements values were 21.8% and 19.7, respectively.

scholarly journals pH-Dependent behaviour of soluble protein aggregates formed during heat-treatment of milk at pH 6·5 or 7·2

2006 ◽  
Vol 73 (1) ◽  
pp. 79-86 ◽  
Author(s):  
Marie Renan ◽  
Omar Mekmene ◽  
Marie-Hélène Famelart ◽  
Fanny Guyomarc'h ◽  
Véronique Arnoult-Delest ◽  
...  
Keyword(s):  
Soluble Protein ◽  
Ph Value ◽  
Skim Milk ◽  
Protein Aggregates ◽  
Heated Milk ◽  
Heat Treated ◽  
Exclusion Chromatography ◽  
Soluble Aggregates ◽  
Ph Dependent ◽  
Dependent Behaviour

The pH-dependent behaviour of soluble protein aggregates produced by the pre-heating of reconstituted skim milk at 90 °C for 10 min was studied, in order to understand the role of these aggregates in acid gelation of heated milk. The following milk samples were prepared: (1) control (unheated reconstituted milk, pH 6·5); (2) milk heat-treated at pH 6·5 (mHtd6·5) and (3) milk heat-treated at pH 7·2 (mHtd7·2). They were centrifuged and the supernatants (SPNT 1) pH-adjusted to yield a series of pH values ranging from 6·5 or 7·2 to 4·6 using HCl at 20 °C or GDL at 20 and 38 °C. pH-Adjusted SPNTs 1 were re-centrifuged. The resulting supernatants (SPNTs 2) were analysed by OD (at 600 and 280 nm) and SDS-PAGE in order to characterise proteins still soluble as a function of pH. Particle size in SPNTs 1 was analysed by Steric Exclusion Chromatography. The OD600 nm revealed that during acidification soluble casein in both control and heat-treated samples exhibits variations in its optical properties or size as previously shown with micellar casein. In heat-treated samples, soluble casein and heat-induced covalent soluble aggregates precipitate at the same pH value. A progressive acidification of the soluble phase did not separate them. Increasing the temperature of acidification from 20 to 38 °C resulted in an increase in the precipitation pH of the proteins. However choice of acidifier did not have a significant effect on OD profiles. The soluble covalent aggregates from mHtd7·2 were smaller, more numerous, and had a higher content of κ-casein than mHtd6·5. Both types of aggregates began to precipitate at the same pH value but precipitation occurred over a narrower pH-range for soluble aggregates prepared from mHtd7·2. This may explain the higher gelation pH of mHtd7·2 compared with mHtd6·5.

Why is the hydrolytic activity of acetylcholinesterase pH dependent? Kinetic study of acetylcholine and acetylthiocholine hydrolysis catalyzed by acetylcholinesterase from electric eel

2018 ◽  
Vol 73 (9-10) ◽  
pp. 345-351 ◽  
Author(s):  
Alena Komersová ◽  
Markéta Kovářová ◽  
Karel Komers ◽  
Václav Lochař ◽  
Alexander Čegan
Keyword(s):  
Catalytic Activity ◽  
Ionic Strength ◽  
Ph Value ◽  
Hydrolytic Activity ◽  
Initial Substrate ◽  
Electric Eel ◽  
Value Range ◽  
Ph Dependent ◽  
Ph Range ◽  
Initial Substrate Concentration

AbstractThe dependence of the activity of acetylcholinesterase from electric eel at a pH value range of 4.8–9.8 (phosphate buffer), regarding acetylcholine and acetylthiocholine hydrolysis, was determined at 25 °C, ionic strength of 0.11 M, and initial substrate concentration of 4 mM. At a pH range of 4.8–9.8, the dependencesA(pH) form a sigmoid increasing curve with the maximum catalytic activity at a pH range 8–9.5. For acetylcholine hydrolysis, the kinetic reason for such an increase inAconsists mainly of an increase in the rate constantk2(Michaelis-Menten) model with increasing pH of the reaction mixture. For acetylthiocholine hydrolysis, the kinetic explication of the determined dependenceA(pH) is more complicated.

pH-Dependent growth of atomic Pd layers on trisoctahedral gold nanoparticles to realize enhanced performance in electrocatalysis and chemical catalysis

Nanoscale ◽  
2018 ◽  
Vol 10 (47) ◽  
pp. 22302-22311 ◽  
Author(s):  
Yahui Song ◽  
Chensheng Xiang ◽  
Cuixia Bi ◽  
Chenshuo Wu ◽  
Hongpeng He ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Chemical Catalysis ◽  
Ph Dependent ◽  
Dependent Growth

Trisoctahedral gold nanoparticles with atomic Pd layers by the pH-dependent growth can be used in catalysis and in situ SERS monitoring.

Colorimetric Study of the Interaction Between Gold Nanoparticles and a Series of Amino Acids

2008 ◽  
Vol 8 (1) ◽  
pp. 353-357 ◽  
Author(s):  
Xiaoli Zhu ◽  
Qianlu Yang ◽  
Junyi Huang ◽  
Iwao Suzuki ◽  
Genxi Li
Keyword(s):  
Amino Acids ◽  
Gold Nanoparticles ◽  
Self Assembly ◽  
Ph Value ◽  
Hydroxyl Groups ◽  
Side Chains ◽  
Interesting Effect ◽  
Colorimetric Study

Study of the interaction between gold nanoparticles and a series of amino acids is reported in this paper. Amino acids with thiol, amine, or hydroxyl groups in their side chains are proven to make gold nanoparticles self-assemble under certain conditions. There is a progression of the effect on self-assembly of gold nanoparticles from hydroxyl < amine < thiol. Meanwhile, concentration of amino acids and the pH value of the solution have been found to be important for amino acids to exert the interesting effect on self-assembly of the nanoparticles.

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