scholarly journals Adsorption/Desorption Behaviors and SERS Chemical Enhancement of 6-Mercaptopurine on a Nanostructured Gold Surface: The Au20 Cluster Model

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5422
Author(s):  
Nguyen Thi Nhat Hang ◽  
Nguyen Thanh Si ◽  
Minh Tho Nguyen ◽  
Pham Vu Nhat
Keyword(s):  
Energy Gap ◽  
Gold Cluster ◽  
Gold Surface ◽  
Binding Mode ◽  
Neutral Solution ◽  
Chemical Enhancement ◽  
Nanostructured Gold ◽  
Protein Matrices ◽  
Adsorption Desorption ◽  
Neutral Conditions

Computational approaches are employed to elucidate the binding mechanism and the SERS phenomenon of 6-mercaptopurine (6MP) adsorbed on the tetrahedral Au20 cluster as a simple model for a nanostructured gold surface. Computations are carried out in both vacuum and aqueous environments using a continuum model. In the gaseous phase and neutral conditions, interaction of 6MP with the gold cluster is mostly dominated by a covalent Au−S bond and partially stabilized by the Au⋅⋅⋅H−N coupling. However, in acidic solution, the nonconventional Au⋅⋅⋅H−S hydrogen-bond becomes the most favorable binding mode. The 6MP affinity for gold clusters decreases in the order of vacuum > neutral solution > acidic medium. During the adsorption, the energy gap of Au20 substantially declines, leading to an increase in its electrical conductivity, which can be converted to an electrical noise. Moreover, such interaction is likely a reversible process and triggered by either the low pH in sick tissues or the presence of cysteine residues in protein matrices. While N−H bending and stretching vibrations play major roles in the SERS phenomenon of 6MP on gold surfaces in neutral solution, the strongest enhancement in acidic environment is mostly due to an Au⋅⋅⋅H−S coupling, rather than an aromatic ring-gold surface π overlap as previously proposed.

scholarly journals Quantum chemical studies of interactions between Au6 cluster and DNA bases

2020 ◽  
Vol 4 (2) ◽  
pp. First
Author(s):  
Nhat Vu Pham ◽  
Nguyen Thanh Si ◽  
Mai Mac Son ◽  
Pham Thi Bich Thao ◽  
Nguyen Van Hong ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Density Functional ◽  
Energy Gap ◽  
Gold Cluster ◽  
Water Environment ◽  
Gold Surface ◽  
Electrical Signal ◽  
Binding Energies ◽  
Basis Set ◽  
Dna Bases

Density functional theory (DFT) is employed to examine the adsorption mechanism of DNA bases (adenine, guanine, cytosine, and thymine) on the gold surface using Au6 cluster as model reactant. Geometries of resulting complexes are optimized using the PBE functional in conjunction with the cc-pVTZ-PP consistent-correlation pseudopotential basis set for gold and the cc-pVTZ basis set for the non-metals. The binding sites and energies, along with several quantum chemical indicators are also investigated at the same level of theory. The binding energies between Au6 cluster and DNA bases are computed to be around 14–25 kcal/mol in gas-phase and slightly reduced to 10 – 20 kcal/mol in the water environment. Cytosine has the highest affinity with gold cluster, decreasing as follows cytosine > adenine  guanine > thymine. If a visible light with a frequency of Hz (500 nm) is applied, the time for the recovery of Au6 from the complexes will be in the range of   (for thymine) to 10 (for cytosine) seconds at 298 K in water. In addition, the geometric structures of both the gold cluster and DNA bases are almost unchanged during the complexation. The gold cluster is found to benefit from a larger change of energy gap that could be converted to an electrical signal for the detection of these molecules. Current results could provide us with fundamentals for understanding the DNA bases absorption on gold nanoparticle surfaces at the atomic and molecular levels.

scholarly journals In Situ Surface-Enhanced Raman Spectroelectrochemical Analysis System with a Hemin Modified Nanostructured Gold Surface

2015 ◽  
Vol 87 (5) ◽  
pp. 2588-2592 ◽  
Author(s):  
Tao Yuan ◽  
Loan Le Thi Ngoc ◽  
Jan van Nieuwkasteele ◽  
Mathieu Odijk ◽  
Albert van den Berg ◽  
...  
Keyword(s):  
Gold Surface ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Nanostructured Gold ◽  
Analysis System

scholarly journals Towards multiple readout application of plasmonic arrays

2011 ◽  
Vol 2 ◽  
pp. 501-508 ◽  
Author(s):  
Dana Cialla ◽  
Karina Weber ◽  
René Böhme ◽  
Uwe Hübner ◽  
Henrik Schneidewind ◽  
...  
Keyword(s):  
Strong Field ◽  
Field Enhancement ◽  
Gold Surface ◽  
Surface Enhanced Raman Spectroscopy ◽  
Metallic Surface ◽  
Simultaneous Application ◽  
Detection Scheme ◽  
Surface Enhanced Raman ◽  
Nanostructured Gold ◽  
Fluorescence Light

In order to combine the advantages of fluorescence and surface-enhanced Raman spectroscopy (SERS) on the same chip platform, a nanostructured gold surface with a unique design, allowing both the sensitive detection of fluorescence light together with the specific Raman fingerprint of the fluorescent molecules, was established. This task requires the fabrication of plasmonic arrays that permit the binding of molecules of interest at different distances from the metallic surface. The most efficient SERS enhancement is achieved for molecules directly adsorbed on the metallic surface due to the strong field enhancement, but where, however, the fluorescence is quenched most efficiently. Furthermore, the fluorescence can be enhanced efficiently by careful adjustment of the optical behavior of the plasmonic arrays. In this article, the simultaneous application of SERS and fluorescence, through the use of various gold nanostructured arrays, is demonstrated by the realization of a DNA detection scheme. The results shown open the way to more flexible use of plasmonic arrays in bioanalytics.

Energy Gap Law for Exciton Dynamics in Gold Cluster Molecules

2017 ◽  
Vol 8 (19) ◽  
pp. 4898-4905 ◽  
Author(s):  
Kyuju Kwak ◽  
Viraj Dhanushka Thanthirige ◽  
Kyunglim Pyo ◽  
Dongil Lee ◽  
Guda Ramakrishna
Keyword(s):  
Energy Gap ◽  
Gold Cluster ◽  
Exciton Dynamics ◽  
Energy Gap Law

scholarly journals Enhanced Photocatalytic Removal of Cyanotoxins by Al-Doped ZnO Nanoparticles with Visible-LED Irradiation

Toxins ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 66
Author(s):  
Majdi Benamara ◽  
Elvira Gómez ◽  
Ramzi Dhahri ◽  
Albert Serrà
Keyword(s):  
Photocatalytic Degradation ◽  
Diffuse Reflectance Spectroscopy ◽  
Degradation Kinetics ◽  
Sol Gel ◽  
Nitrogen Adsorption ◽  
Zno Nanoparticle ◽  
Al Content ◽  
Doped Zno ◽  
Adsorption Desorption ◽  
Neutral Conditions

The ZnO-based visible-LED photocatalytic degradation and mineralization of two typical cyanotoxins, microcystin-LR (MC-LR), and anatoxin-A were examined. Al-doped ZnO nanoparticle photocatalysts, in Al:Zn ratios between 0 and 5 at.%, were prepared via sol-gel method and exhaustively characterized by X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, and nitrogen adsorption-desorption isotherms. With both cyanotoxins, increasing the Al content enhances the degradation kinetics, hence the use of nanoparticles with 5 at.% Al content (A5ZO). The dosage affected both cyanotoxins similarly, and the photocatalytic degradation kinetics improved with photocatalyst concentrations between 0.5 and 1.0 g L−1. Nevertheless, the pH study revealed that the chemical state of a species decisively facilitates the mutual interaction of cyanotoxin and photocatalysts. A5ZO nanoparticles achieved better outcomes than other photocatalysts to date, and after 180 min, the mineralization of anatoxin-A was virtually complete in weak alkaline medium, whereas only 45% of MC-LR was in neutral conditions. Moreover, photocatalyst reusability is clear for anatoxin-A, but it is adversely affected for MC-LR.

Protein-Metal Interactions Probed by SERS: Lysozyme on Nanostructured Gold Surface

Plasmonics ◽  
2018 ◽  
Vol 13 (6) ◽  
pp. 2117-2124 ◽  
Author(s):  
N. R. Agarwal ◽  
M. Tommasini ◽  
E. Ciusani ◽  
A. Lucotti ◽  
S. Trusso ◽  
...  
Keyword(s):  
Gold Surface ◽  
Metal Interactions ◽  
Nanostructured Gold

Formation of abnormally large-sized tubular amyloid β aggregates on a nanostructured gold surface

2010 ◽  
Vol 28 (1) ◽  
pp. 184-188
Author(s):  
Jeongjin Lee ◽  
Junsu Park ◽  
Byoung Kyu Kwak ◽  
Inhee Choi ◽  
Younghun Kim ◽  
...  
Keyword(s):  
Amyloid Β ◽  
Gold Surface ◽  
Nanostructured Gold

scholarly journals A computational study of mercaptopurine and thioguanine binding to gold clusters Aun (n = 3, 4)

2021 ◽  
Vol 10 (3) ◽  
pp. xx-xx
Author(s):  
Si Nguyen Thanh ◽  
Huyen Duong Thi ◽  
Thao Pham Thi Bich ◽  
Kha Tran Ni ◽  
Nhat Pham Vu
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Density Functional Theory Calculations ◽  
Gold Surface ◽  
Gold Clusters ◽  
Drug Binding ◽  
Basis Set ◽  
Release Mechanism ◽  
Water Solvent ◽  
Protein Matrices

The density functional theory calculations are employed to elucidate the adsorption/desorption behaviours of mercaptopurine (MP) and thioguanine (TG) drugs on the gold surfaces, using Au3 and Au4 clusters as model reactants. The PBE functional in combination with the effective core potential cc-pVTZ-PP basis set for gold atoms and cc-pVTZ basis set for nonmetals have been used to investigated geometric structures, thermodynamic parameters and electronic properties of the obtained complexes. The IEF-PCM model with water solvent was used to include the effect of biological environment on the interactions. The computed results show that the binding is dominated by a covelant bond Au−S and by electrostatic effects, namely a hydrogen bond contribution NH∙∙∙Au. In addition, the drug binding to gold clusters is a reversible process and a drug release mechanism was also clarified. Accordingly, the drugs are willing to separate from the gold surface due to either a slight change of pH in tumor cells or the presence of cysteine residues in protein matrices.

A Raman and SERS study on the interactions of aza[5]helicene and aza[6]helicene with a nanostructured gold surface

2020 ◽  
Vol 111 ◽  
pp. 103180
Author(s):  
Chiara Zanchi ◽  
Andrea Lucotti ◽  
Matteo Pistaffa ◽  
Paolo M. Ossi ◽  
Sebastiano Trusso ◽  
...  
Keyword(s):  
Gold Surface ◽  
Nanostructured Gold
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