Deposition of fluorescent NIPAM-based nanoparticles on solid surfaces: Quantitative analysis and the factors affecting it

• A novel fluorescent temperature-sensitive nanoparticle, p(NIPAM) 5% VC, was synthesized.
• Quantitative analysis of the deposition of nanoparticles on different surfaces was carried out.
• A combination of factors affects the mass of nanoparticles deposited on surfaces.
• Surface charge, surface roughness and temperature highly affect the mass of nanoparticles deposited on different surfaces.
• The hydrophilicity/hydrophobicity of the surface has minimal effect on the deposition of nanoparticles.

Recently, responsive surfaces have attracted attention due to their potential applications. Reported research have studied the deposition of environmentally responsive particles on different surfaces, qualitatively tested their response to environmental conditions and studied their possible applications. In this work, novel fluorescent temperature-sensitive nanoparticles were synthesized using a surfactant free emulsion polymerization technique: poly(N-isopropylacrylamide-co-5% vinyl cinnamate) (p(NIPAM)5%VC). The new particles were characterized using dynamic light scattering and fluorescence spectroscopy. A novel sensitive method for the quantitative analysis of p(NIPAM) 5% VC using fluorescence spectroscopy was developed to determine the concentration of nanoparticle dispersions. This was further used to quantitatively determine the mass of nanoparticles deposited per unit area of glass pre-treated with acid, glass pre-treated with base, quartz, stainless steel, gold and teflon at 25 °C and 60 °C. Factors affecting the adsorption/desorption of the nanoparticles were studied, including the effect of substrate surface charge, surface roughness (using atomic force microscopy, AFM), hydrophilicity/hydrophobicity and the temperature at which the adsorption/desorption experiments were carried out. The results show that the effect of surface charge is the most significant, followed by that of surface roughness and temperature. Meanwhile, the influence of the hydrophobicity/hydrophilicity of the surface on the adsorption/desorption of nanoparticles appears to be far less significant than the previously mentioned factors.

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