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    Home > Angelw: nano silver incarnation colorimetric detector, easy to determine trace harmful gases

    Angelw: nano silver incarnation colorimetric detector, easy to determine trace harmful gases

    • Last Update: 2019-08-19
    • Source: Internet
    • Author: User
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    The non sintering aggregation of metal nanoparticles (especially gold or silver) is an important kind of colorimetric and fluorescent sensors, which are widely used in the detection of biomacromolecule analytes These sensors rely on the changes of local surface plasmon resonance (LSPR) of nanoparticles, and detect biomacromolecules by the aggregation of nanoparticles caused by the combination of biomacromolecules and nanoparticles Silver nanoparticles (AGNPS) are widely used in environmental monitoring, pharmaceutical, food safety, safety screening and so on However, in addition to no 2, H 2S and NH 3, few studies attempt to use AgNPs to detect other small molecules in gas Recently, Professor Kenneth s Suslick of the University of Illinois at Urbana Champaign found that the existing silver nanoparticles (AGNPS) can grow in solid state even if they are exposed to only a small amount of active gas at room temperature This chemical induced sintering of nanoparticles and the resulting LSPR changes the visible absorbance and color of AgNPs, providing a new potential mechanism for the trace and cumulative dose determination of active gases The relevant research results were published on angelw Chem Int ed (DOI: 10.1002/anie.201908600) (image source: angelw Chem Int ed.) the author synthesized different ligand modified AgNPs (Figure 1) with a size of about 10nm, and detected the crystal form and surface ligands of AgNPs by a series of methods When these AgNPs are exposed to the active gas (not N2 or other non active gas), they will be sintered (Figure 2) The nanoparticles remain intact, but the contact place will be fused together The possible mechanism is the diffusion of particles and the cold welding of the complete particles, and finally a large aggregate will be formed The speed and extent of sintering depends on the activity of the contact gas Once exposed to these active gases, the ligand molecules on the surface of AgNPs are oxidized or protonated The acid gas causes the molecules on the surface of AgNPs to fall off after protonation, so AgNPs will gather quickly; this acid catalysis depends on the pKa of the ligand molecules, the larger the pKa, the easier the protonation Oxidation gas will lead to the oxidation of ligand molecules, and the binding force between the generated molecules and AgNPs will be weakened, so the particles will start to gather after falling off However, the less active gases (such as N2, Co, NH3, HCHO, toluene vapor) have less effect on the morphology of AgNPs The active gas can also cause the absorption band of AgNPs powder to shift and the color to change, which is irreversible (image source: angelw Chem Int ed.) in the past, some colorimetric sensor array (CSA) based on chemical reactive dyes have been developed, but these tests are reversible and cannot detect the cumulative effect of analytes Next, the active gas was identified by CSA based on AgNPs The hydrophobic AgNPs ink was diluted to different concentrations and then sprayed on the hydrophobic polypropylene film Then different gases were detected The results show that these AgNPs can be used to detect various active gases in a way that depends on concentration and surface ligands (Figure 3) Through the sequence cluster analysis (HCA), the author found that 11 kinds of active gases with concentration of 1 ppm could be distinguished from this kind of CSA Considering that this kind of CSA is an irreversible cumulative detection, its detection limit should be far lower than this concentration It has been proved that its detection limit can reach the concentration of sub ppb In addition, this CSA is not sensitive to CO2 and humidity in the environment, so it will not be affected by environmental factors (picture source: angelw Chem Int ed.) in general, this study has developed a convenient, simple, sensitive and stable method for the detection of trace active gas CSA, which can be distinguished by naked eyes, by using the different properties of the surface ligands of AgNPs In addition, this CSA is not sensitive to CO2 and humidity in the environment, and it is irreversible, so it does not need real-time observation and imaging, and can detect the accumulation of environmental pollutants Therefore, this method has great potential in the detection of trace harmful gases.
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