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Effective GQD/AuNPs nanosensors for selectively bifunctional detection of lysine and cysteine under different photophysical properties
摘要： This work presented the development of the optical nanosensor based on AuNPs and GQDs which perform the efficiency dual optical sensor. Importantly, the AuNPs with GQDs was prepared by one-pot chemical reaction by using GQDs as an excellent bifunction of the reducing agent and stabilizer to obtain the disaggregated AuNPs/GQDs in red color property. Apart from its photophysical sensing ability, this hybrid material demonstrated the dual sensing of cysteine and lysine regarding to colorimetric and fluorometric techniques, respectively, in PBS solution pH 7.4. The presence of Cys in the AuNPs/GQDs solution rapidly lead to the color change from red to blue with concomitant of the red shift of the absorption band at 525 to 645 nm undergone the aggregation process. On the other hand, AuNPs/GQDs nanosensor in the presence of Lys performs the off-on fluorescence at 450 nm without color change in PBS solution pH 7.4. Interestingly, no interference of any amino acids towards Cys and Lys detection highlighted a high efficacy in selective sensing aspect. For sensing application, the detection limit of Cys and Lys was 5.88 μM and 16.14 μM, respectively, with an acceptable % recovery of 101–106 in real samples.
关键词： Graphene quantum dot,Gold nanoparticles,Aggregation,Lysine,Cysteine,Displacement
更新于2025-09-10 09:29:36
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Visible Light-Promoted Plasmon Resonance to Induce “Hot” Hole Transfer and Photothermal Conversion for Catalytic Oxidation
摘要： Titanium dioxide (TiO2) semiconductor photocatalysts were photosensitized to the visible spectrum with gold nanospheres (AuNSs) and gold nanorods (AuNRs) to study the ethanol photo-oxidation cycle, with an emphasis towards driving carbon-carbon (C-C) bond cleavage at low temperatures. The photocatalysts exhibited a localized surface plasmon resonance (SPR) that was harnessed to drive the complete photo-oxidation of formic acid (FA) and ethanol (EtOH) via augmented carrier generation/separation and photothermal conversion. Contributions of transverse and longitudinal localized SPR modes were decoupled by irradiating AuNSs-TiO2 and AuNRs-TiO2 with targeted wavelength ranges to probe their effects on plasmonically-assisted photocatalytic oxidation of FA and EtOH. Photocatalytic performance was assessed by monitoring the yield of gaseous products during photo-oxidation experiments using a gas chromatography-mass spectrometry-multiple headspace extraction (GC-MS-MHE) analysis method. The complete oxidation of EtOH to CO2 under visible-light irradiation was confirmed by GC-MS-MHE for both AuNSs and AuNRs on TiO2 at room temperature. Photothermal and local field enhancements were found to aid in selectively cleaving the C-C bond in EtOH to form FA, while FA was further oxidized to CO2 by plasmon-induced electron transfer mechanisms. Under visible light (>420 nm) irradiation, carrier generation/separation and photothermal conversion was achieved, resulting in the photogenerated “hot” holes driving the photo-oxidation primarily on the AuNPs. Specifically, plasmonic enhancement by AuNR-TiO2 enhances EtOH oxidation, providing a method to selectively cleave C-C bonds.
关键词： Carbon-carbon bond cleavage,Photocatalysis,Hybrid Materials,Gold nanoparticles,Ethanol oxidation,Magnetic,Formic acid oxidation,Plasmonics,TiO2,Optical
更新于2025-09-10 09:29:36
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Precise Nanoparticle – Reactant Interaction Outplays Ligand Poisoning in Visible-Light Photocatalysis
摘要： Metal nanoparticles (NPs) and ligands are two inseparable entities. However, ligands present on the surface of NPs can ‘poison’ a photocatalyst by hindering the NP accessibility to reactants and the movement of charge carriers. Here we present an elegant strategy to accomplish efficient photocatalysis by taking advantage of ligands on the NP surface. Our approach of introducing favorable interactions between NP catalyst and reactant is tested in the model photocatalytic reduction of ferricyanide by gold nanoparticles (AuNP). The favorable interaction arising from the precise tuning of electrostatic potential results in the localization of reactants around the AuNP catalyst. The close proximity between AuNP and ferricyanide improves the NP accessibility and electron transfer rate, thereby suppressing the ligand poisoning effect. Such interaction driven enhancement in photocatalytic performances can be prominent in the emerging area of ‘ligand directed product formation’ in NP catalysis.
关键词： Nanoparticles,Gold Nanoparticles,Ligand Poisoning,Electrostatic Interaction,Photocatalysis
更新于2025-09-09 09:28:46
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Dynamics of gold nanoparticle clusters observed with liquid-phase electron microscopy
摘要： The dynamics of processes of nanoparticles such as diffusion, attraction and repulsion, and self-assembly of structures of nanoparticles at the solid-liquid interfaces differ significantly from those occurring for bulk conditions and their fundamental physical rules are still unknown. Here, we used liquid phase scanning transmission electron microscopy (LP-STEM) to study several aspects of nanoparticle dynamics of colloidal chitosan coated gold nanoparticle (TCHIT-AuNP) clusters in a liquid layer enclosed between two SiN membranes. We found that upon beam irradiation using an electron flux of 0.9 e?/s?2, the AuNPs assembled in clusters that shifted and rotated with time. The newly formed clusters could join and form larger clusters via a mechanism of oriented attachment. By increasing the electron flux to 6.2 e?/s?2, we observed the fragmentation of some of the clusters and TCHIT-AuNPs were exchanged between clusters. At the highest electron flux studied 25 e?/s?2, we observed AuNPs moving at a very slow speed compared to Brownian motion in liquid even though they were not permanently attached or pinned to the liquid-enclosing membrane. Experiments using branched polyethylenimine (BPEI) coated AuNPs were carried out for comparison.
关键词： nanoparticle clustering,nanoparticle dynamics,solid-liquid interface,gold nanoparticles,scanning transmission electron microscopy,liquid-phase electron microscopy
更新于2025-09-09 09:28:46
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Variable Growth and Characterizations of Monolayer Protected Gold Nanoclusters Based on Molar Ratio of Gold and Capping Ligands
摘要： Controlling the size of nanoscale entities is important because many properties of nanomaterials are directly related to the size of the particles. Gold nanoparticles represent classic materials and are of particular interest due to their potential application in a variety of fields. In this study, hexanethiol-capped gold nanoparticles are synthesized via the Brust-Schiffrin method. Synthesized nanoparticles were characterized by various analytical techniques such as transmission electron microscopy (TEM), scanning tunneling microscopy (STM), UV-Visible absorption spectroscopy (UV-Vis) and electrochemical techniques. We have varied the molar ratio of gold to the protecting agent (hexanethiol) to discover the effect of gold-to-hexanethiol ligand ratio on the size of gold clusters. The clear correlation between cluster size and molar ratio is found that the averaged cluster size decreases from 4.28 ± 0.83 nm to 1.54 ± 0.67 nm as the gold-to-ligand molar ratio changes from 1:1 to 1:9. In contrast to a recent report that thiolated gold nanoparticles are under spontaneous disintegration when they are assembled on a gold substrate, our STM experiments proved that these gold nanoparticles can form a stable monolayer or multiple layers on the platinum electrode without observing disintegration within 72 hours. Therefore, our STM experiments demonstrate that the disintegration behavior of gold nanoparticles is related to the type of ligands and the nature of substrate materials. In electrochemical experiments, these gold nanoparticles displayed an electrochemical quantized charging effect, making these nanoparticles useful in the device applications such as electrochemical or biological sensors.
关键词： particle size,electrochemistry,molar ratio,Gold nanoparticles,STM,disintegration
更新于2025-09-09 09:28:46
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Colorimetric detection of cysteine based on dispersion - aggregation of chitosan stabilized gold nanoparticles
摘要： A simple and selective colorimetric method of detection of cysteine using chitosan stabilized gold nanoparticles has been developed. L-cysteine is a sulfur containing amino acid. Cysteine binds with the gold nanoparticles through sulfur group and induces aggregation of the nanoparticles which leads to an apparently visible color change from pale red to blue. A good linearity was observed from 0.1 to 30 μM (R=0.9958) cysteine and the limit of detection was found to be 0.1 μM. The gold nanoparticles showed a high selectivity towards the detection of cysteine even in the presence of 10,000 fold higher concentration of common interferences such as glutathione, methionine and homocysteine. A plausible mechanism for the selective detection of cysteine in presence of interferences based on a dispersion-aggregation mechanism has been proposed.
关键词： Sensitivity,Chitosan,Gold nanoparticles,Colorimetric sensor,Cysteine
更新于2025-09-09 09:28:46
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Characterization of Polylactide-Stabilized Gold Nanoparticles and Its Application in the Fabrication of Electrochemical DNA Biosensors
摘要： In this work, two different approaches to gold nanoparticles (AuNPs) have been explored for the modification of screen-printed electrode based on AuNPs and AuNPs stabilized with polylactic acid (PLA). The modified substrate has been characterized using UV-Vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) and cyclic voltammetry. Both synthesized AuNPs were studied in terms of stability, sensitivity and reproducibility to enhance the sensing capability of modified electrodes. The PLA-stabilized AuNPs form strong structured nanoparticles and stabilize in aqueous solution. A larger active surface area (0.41 cm2) and lower charge transfer resistance (Rct) value were reported in the modification of sensing material with PLA-stabilized AuNPs, which resulted in enhancement of sensitivity. Therefore, AuNPs in PLA can be used as a potential alternative modifier for sensing chemicals and biomolecules in electrochemical sensors.
关键词： gold nanoparticles,polylactic acid,screen-printed carbon electrode,electrochemical DNA biosensor
更新于2025-09-09 09:28:46
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A Versatile Dynamic Light Scattering Strategy for the Sensitive Detection of Plant MicroRNAs Based‐on Click Chemistry‐Amplified Aggregation of Gold Nanoparticles
摘要： Plant microRNAs (miRNAs) are naturally 2′-O-methylated at the 3′-terminal, so they cannot be efficiently detected by traditional target-triggered polymerization reactions. Herein, a simple but robust enzyme-free sensing strategy is developed for plant miRNA analysis by using dynamic light scattering (DLS) technique to monitor the click chemical ligation-amplified crosslinking of gold nanoparticles (AuNPs). Combining the enzyme-free cycling chemical ligation-mediated signal amplification, and the intrinsic outstanding ability of DLS for discriminating the extremely low level of particle aggregation in a large pool of monodisperse AuNPs, high sensitivity is achieved and as low as 78.6 fM plant miRNA can be easily detected.
关键词： crosslinking,click chemistry,plant microRNA,dynamic light scattering (DLS),gold nanoparticles
更新于2025-09-09 09:28:46
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Nanoparticles at Biomimetic Interfaces: A Combined Experimental and Simulation Study on Charged Gold Nanoparticles/Lipid Bilayers Interfaces
摘要： The poor understanding of the interaction of nanomaterials with biologically relevant interfaces is recognized as one of the major issues currently limiting the development of nanomedicine. The central purpose of this study is to compare experimental (Confocal Microscopy, Fluorescence Correlation Spectroscopy, X-ray Reflectivity) and computational (Molecular Dynamics simulations) results to thoroughly describe the interaction of cationic gold nanoparticles (AuNP) with mixed zwitterionic/anionic lipid membranes. The adhesion of AuNPs to the lipid membrane is investigated on different length scales from a structural and dynamical point of view; with this approach, a series of complex phenomena, spanning from lipid extraction, localized membrane disruption, lateral phase separation and slaved diffusion, are characterized and interpreted from a molecular level to macroscopic observations.
关键词： Nanoparticles,Gold Nanoparticles,Molecular Dynamics,X-ray Reflectivity,Fluorescence Correlation Spectroscopy,Lipid Bilayers,Biomimetic Interfaces,Confocal Microscopy
更新于2025-09-04 15:30:14
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Facile Functionalization of Gold Nanoparticles with PLGA Polymer Brushes and Efficient Encapsulation into PLGA Nanoparticles: Toward Spatially Precise Bioimaging of Polymeric Nanoparticles
摘要： Nanocarriers prepared from poly(lactide-co-glycolide) (PLGA) have broad biomedical applications. Understanding their cellular uptake and distribution requires appropriate visualization in complex biological compartments with high spatial resolution, which cannot be offered by traditional imaging techniques based on fluorescent or radioactive probes. Herein, the encapsulation of gold nanoparticles (GNPs) into PLGA nanoparticles is proposed, which should allow precise spatial visualization in cells using electron microscopy. Available protocols for encapsulating GNPs into polymeric matrices are limited and associated with colloidal instability and low encapsulation efficiency. In this report, the following are described: 1) a facile protocol to functionalize GNPs with PLGA polymer followed by 2) encapsulation of the prepared PLGA-capped GNPs into PLGA nanocarriers with 100% encapsulation efficiency. The remarkable encapsulation of PLGA-GNPs into PLGA matrix obeys the general rule in chemistry “like dissolves like” as evident from poor encapsulation of GNPs capped with other polymers. Moreover, it is shown that how the encapsulated gold nanoparticles serve as nanoprobes to visualize PLGA polymeric hosts inside cancer cells at the spatial resolution of the electron microscope. The described methods should be applicable to a wide range of inorganic nanoprobes and provide a new method of labeling pharmaceutical polymeric nanocarriers to understand their biological fate at high spatial resolution.
关键词： phase transfer,gold nanoparticles,encapsulation,PLGA
更新于2025-09-04 15:30:14