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Effect of Size, Coverage, and Dispersity on the Potential-Controlled Ostwald Ripening of Metal Nanoparticles
摘要： Here we describe the size-dependent, electrochemically-controlled Ostwald ripening of 1.6, 4 and 15 nm diameter Au nanoparticles (NPs) attached to (3-aminopropyl)triethoxysilane (APTES)-modified glass/Indium tin oxide (glass/ITO) electrodes. Holding the Au NP-coated electrodes at a constant potential negative of the dissolution potential in bromide-containing electrolyte led to electrochemical Ostwald ripening of the different-sized Au NPs. The relative increase in the diameter of the NPs (Dfinal/Dinitial) during electrochemical Ostwald ripening increases with decreasing NP size, increasing applied potential, increasing NP population size dispersity, and increasing NP coverage on the electrodes. Monitoring the average size of the Au NPs as a function of time at a controlled potential allows the measurement of the Ostwald ripening rate. Anodic stripping voltammetry (ASV) and electrochemical determination of the surface area-to-volume ratio (SA/V) provides fast and convenient size analysis for the many different samples and conditions, with consistent sizes from scanning electron microscopy (SEM) images for some samples. It is important to better understand electrochemical Ostwald ripening, especially under potential control, since it is a major process that occurs during the synthesis of metal NPs and leads to detrimental size instability during electrochemical applications.
关键词： electrochemical control,surface area-to-volume ratio,anodic stripping voltammetry,size-dependent,metal nanoparticles,Ostwald ripening
更新于2025-09-23 15:19:57
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Direct culture-free electrochemical detection of cells in milk based on quantum dots-modified nanostructured dendrons
摘要： With regard to global food safety and preventing the spread of diseases caused by foodborne pathogens or their toxins, there is an increasing need for simple and rapid methods for the screening of such pathogens. We aimed to develop a fast and efficient biosensor for the screening of milk samples contaminated by Salmonella spp. and provide a quick and cost-effective method as an alternative to the time-consuming conventional cultivation- or PCR-based approaches. We exploited a simple but highly specific technique whereby bacterial cells were separated immunomagnetically, with subsequent reaction with conjugate; i.e. specific IgG molecule labelled with an electrochemically potent indicator. The unique structure of this indicator exploits the benefits of hyperbranched dendron molecules and heavy metal–derived quantum dots (QDs). Square-wave anodic stripping voltammetry (SWASV) using of screen-printed carbon electrodes with in situ formed Bi(III) film (BiSPCE) was used for the detection and quantification of metal ions released from the QDs (CdTe) after their acidic dissolution. The metal ion signals proportionally correlate with the amount of captured bacteria cells. By this method, the presence of Salmonella spp. was proven in 2.5 hours even in minimal number of bacterial cells (4 CFU) in 1 mL of the sample.
关键词： Salmonella spp.,Electrochemical immunosensor,Quantum dots,Stripping voltammetry,Foodborne pathogen,Nanostructured dendrons
更新于2025-09-19 17:13:59
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Voltammetric immunoassay of human IgG based on the release of cadmium(II) from CdS nanocrystals deposited on mesoporous silica nanospheres
摘要： The authors describe a nanocomposite that was obtained by in-situ deposition of CdS nanocrystals on mesoporous silica nanospheres (MSNs), and its use in an electrochemical immunoassay of human immunoglobulin G (HIgG). The MCN/CdS nanocomposite was covalently modified with the antibodies against HIgG and then employed in a voltammetric immunoassay at antibody-functionalized magnetic beads. Through sandwich immunoreaction, the MCN/CdS nanoprobes are quantitatively captured onto the magnetic beads where numerous Cd(II) ions are released in an acidic solution. The Cd(II) can be detected by anodic stripping voltammetry at a typical working potential of ?0.78 V (vs. Ag/AgCl). In combination with the high loading of CdS on MSNs, the use of the stripping voltammetric analysis renders the method high sensitivity. A wide linear range varying from 0.01 to 100 ng mL?1 is obtained for HIgG detection with a lower detection limit at 2.9 pg mL?1. In addition, the preparation of the nanoprobe is inexpensive. The magnetic bead-based assay does not require complex manipulations. Therefore, this method is deemed to possess a wide scope in that it may be applied to other immunoassays.
关键词： Magnetic beads,Anodic stripping voltammetry,Immunosensor,Nanoprobe,Signal amplification
更新于2025-09-04 15:30:14