(a) Specially designed microfluidics chip for the measurement of ultrafast kinetics. Two specific regions are shown: X, for fast sub-100 ns kinetics and Y, for slower kinetics. (b) A fast ionic model reaction between sodium hydroxide and phenolphthalein measured in the microfluidics chip (X region) on the microsecond time scale is shown. (c) The “flow-stopped” methodology applied to the same ionic reaction at a fixed position (Y region) of the micro-channel without any flow of the reactants is shown. The snapshots reveal the role of diffusion in the ongoing reaction (see text).
(a) Schematic presentation of the developed microfluidics platform. L denotes the flow path length, Xi are the positions for measurements along the channel, and S is the cross section of the micro-channel. (b) The fluorescence microscope coupled to the microfluidics channel. A CCD camera captures images of the ongoing reactions inside the micro-channel. (c) Picosecond-resolved fluorescence technique (TCSPC) for the collection of decay profiles along the micro-channel. (d) Femtosecond upconversion technique combined with the microfluidics platform for studying ultrafast dynamics.
(a) Fluorescence intensity profile of H33258 in the complexation reaction with SDS (red dots). Fluorescence images showing the extent of the reaction along the microfluidics channel as revealed by the increase in fluorescence intensity and change in the fluorescence maximum (inset images). Picosecond-resolved fluorescence transients of H33258 (inset traces) depicting the dynamical lifetime of H33258 along the channel (blue triangles). Solid and dotted lines indicate the fit of the experimental data with the appropriate kinetic equation as described in the text. (b) Depicts the change in the fluorescence emission maximum in the course of the complexation. A, B, and C denotes three positions along the micro-channel as shown in the upper panel of the figure. The emission maximum is blue shifted from 500 nm (A), to 485 nm (B), and finally to 470 nm (C).
Fluorescence intensity profile of H33258 in the complexation reaction with CTAB (a) and TX100 (b), respectively. Fluorescence images (insets) showing the extent of the reaction along the microfluidics channel as revealed by the increase in fluorescence intensity. Picosecond-resolved fluorescence transients of H33258 (inset traces) depicting the dynamical lifetime of H33258 along the channel during the complexation.
Fluorescence intensity profile of EtBr along the micro-channel as obtained from the fluorescence microscope. The complexation of the probe EtBr with the SDS micelle (a) and the three step intercalation process of the probe into the DNA (b) are shown. Dashed lines indicate the fits of the experimental data (dots) to the appropriate kinetic equations as described in the text. The inset of (a) depicts the fluorescence intensity profile of EtBr-TX100 complexation.
(a) Schematic showing the formation of the intermediate charge complex for the molecular recognition of SDS micelles with H33258. (b) One-step molecular recognition of TX100 and CTAB micelles with H33258. (c) Schematic of DNA-EtBr interactions. Din, Dint, and Dout are the dielectric values at the DNA centre, at the DNA surface and in bulk water, respectively. The scheme describes the multi-step intercalation process of EtBr into the DNA.
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