International audienceA simple group theory approach is proposed to predict the charge distribution of low order localized surface plasmon resonances (LSPRs) of finite metallic particles of basic geometries. As an illustration, the case of randomly oriented Au colloidal particles of cubic C$_{4v}$ symmetry excited at dipolar resonance is presented. The symmetry approach is confirmed by numerical simulations carried out by the $boundary$ $element$ $method$. Experimental validation is achieved by high-resolution subwavelength near-field mapping conducted by $photoemission$ $electron$ $microscopy$
Singlet Oxygen Sensor Green (SOSG) is the most widely used fluorescent probe for detecting singlet oxygen (1 O 2). 1 O 2 can be efficiently produced by exciting the surface plasmon of gold nanoparticles with laser pulses. However, gold nanoparticles are usually embedded in a chemical stabilizer that can interact with SOSG, leading to erroneous detection of 1 O 2. This article shows that the emission properties of SOSG strongly depend on the concentration of cetyltrimethylammonium bromide (CTAB), a capping agent widely used for nanoparticles synthesis and stabilization. The sensitivity of SOSG to 1 O 2 is also drastically affected by the presence of CTAB. This effect is due to the fluorescent probe's aggregation in CTAB premicellar aggregates and micelles, and the change in the probe configuration. Furthermore, the behavior of SOSG in the presence of two other widely-used surfactants, i.e., citrate and Polyethylene Glycol (PEG), is investigated to determine the right nanoparticle stabilizer to use with SOSG probe.
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