Mesoporous silica derivatives in random optical fields

In this study, we demonstrate label-free optical differentiation and motion hindrance of pristine MCM-41 and surface-modified MCM-41GA using random optical fields, also known as speckle tweezers (STs), within a microfluidic environment. MCM-41 (S_BET = 800 m² g^-1, pore diameter = 2.0 nm, <i>ζ</i> = -30 mV) and MCM-41GA (S_BET = 450 m² g^-1, pore diameter = 1.8 nm, <i>ζ</i> = 4 mV) are synthesized and structurally characterized by XRD, NMR, SEM, TGA, elemental analysis, and N₂ sorption. Quantitative trajectory analysis reveals that illumination with a random optical field suppresses particle motility in both materials. For MCM-41, the mean velocity decreases from 8.9 to 8.0 <i>μ</i>ms^-1 (Welch's <i>p</i> value ≈ 2.2 × 10^-2), while for MCM-41GA, the mean velocity decreases from 4.4 to 3.6 <i>μ</i>ms^-1 (Welch's <i>p</i> value ≈ 8 × 10^-3). Overall, ST induces a consistent reduction in the mean particle velocity and a marked increase in the immobility, enabling optically driven, physicochemical-dependent spatial segregation of mesoporous silica particles within microfluidic chips.