Reactions in ultra-small droplets by tip-assisted chemistry

Abstract

The confinement of chemical reactions within small droplets has received much attention in the last few years. This approach has been proved successful for the in-depth study of naturally occurring chemical processes as well as for the synthesis of different sets of nanomaterials with control over their size, shape and properties. Different approaches such as the use of self-contained structures or microfluidic generated droplets have been followed over the years with success. However, novel approaches have emerged during the last years based on the deposition of femtolitre-sized droplets on surfaces using tip-assisted lithographic methods. In this feature article, we review the advances made towards the use of these ultra-small droplets patterned on surfaces as confined nano-reactors.

A Comparative Study of Thiol‐Terminated Surface Modification by Click Reactions: Thiol‐yne Coupling versus Thiol‐ene Michael Addition

“…The deposited volumes range over several orders of magnitude from DPN (low attoliter) to inkjet printing (pico‐ to nanoliter), with µCS (low femtoliter) being in the middle of this range . These size differences are expected to also effect chemical reactions inside the droplets and at the droplet/surface interface due to convection, diffusion length, and drying effects . In conclusion, when surface chemistry for µCS can be chosen free of other concerns, the TEMA reaction will yield most efficient surface immobilization.…”

Resonance in Chirogenesis and Photochirogenesis: Colloidal Polymers Meet Chiral Optofluidics

“…These reactions and processes confined in the microdroplets differ from the conventional chemistry in homogeneous solutions. The reactions involve protein unfolding [178], helix formation [179], phosphorylation in ribonucleosides [176,177], production of nanostructures [180], autoreduction [181], and so on. Although the oil/water, air/water, and silica/water interfaces are used as the platforms, the cause of the acceleration mechanisms in these microdroplets is as a matter of debate.…”

Scale-up of microdroplet reactions by heated ultrasonic nebulization

“…A number of recent studies, 1-11 including work of our own, [12][13][14][15][16] have reported the acceleration of reaction rates in microdroplets formed in the course of spray-based ionization 4, 13,17 and microuidics. 18,19 Microdroplets show a strikingly different reactive environment from that of the corresponding bulk phase. 5,18,20 The alteration of pH, 21 accumulation of reagents 5 on the microdroplet surface, solvent evaporation, connement of reagents, and high surface-to-volume ratio of microdroplets are thought to contribute to the reaction acceleration.…”