Spatially Mediated Paper Reactors for On-Site Multicoded Encryption

This report develops a point-of-use chemical trigger and applies it to a dual-functional chemical encryption chip that enables manual and digital identification with enhanced coding security levels suitable for on-site information verification. The concept relies on conducting continuous chemical synthesis and chromatographic separation of specified compounds on a paper device in a straightforward sketch. In addition to single-step chemical reactions, cascade syntheses and operations involving components of distinct mobilities are also demonstrated. The condensation of dione and hydrazine is first demonstrated on a linear paper reactor, where precursors can mix to react, followed by final product separation under optimized conditions. This linear paper reactor design can also support a multistep cascade Wittig reaction by controlling the relative mobility of reactants, intermediates, and final products. Furthermore, a three-dimensional paper reactor with appropriate mobile phases helps to initiate complex solvent system-driven azide-alkyne cycloaddition. By the use of a three-dimensional device design for spatially limited interdevice reactant transportation, reactants crossing designated boundaries trigger confined chemical reactions at specific positions. Accumulation of repetitive reactions leads to successful product gradient generation and mixing effects, representing a fully controllable intersubstrate chemical operation on the platform. Standing on initiating desired chemical reactions at particular interface regions, integration of appropriate selective reaction area, numerical digits overlay, color diversity, and mobile recognition realizes this dual-functional multicoding encryption process.

Total Internal Reflection Transient Absorption Microscopy: An Online Detection Method for Microfluidics

Microreactors have garnered widespread attention for their tunability and precise control of synthetic parameters to efficiently produce target species. Despite associated advances, a lack of online detection and optimization methods has stalled the progression of microfluidic reactors. Here we employ and characterize a total internal reflection transient absorption microscopy (TIRTAM) instrument to image excited state dynamics on a continuous flow device. The experiments presented demonstrate the capability to discriminate between different chromophores as well as in differentiating the effects of local chemical environments that a chromophore experiences. This work presents the first such online transient absorption measurements and provides a new direction for the advancement and optimization of chemical reactions in microfluidic devices.

Threading-gated photochromism in [2]pseudorotaxanes

Rigid, Y-shaped imidazole compounds containing the bis(thienyl)ethene moiety were designed and synthesized. The 4,5-bis(benzothienyl)-2-phenylimidazolium cations were then used as axles for [2]pseudorotaxane formation with 24-membered crown ether wheels. It was demonstrated using 1H NMR spectroscopy, UV-Vis absorption and emission spectroscopies that this host-guest interaction results in significant changes in the photochromic properties of the imidazolium axles. This is a rare example of gated photochromism, which exploits the recognition event of an interpenetrated molecular system to tune the photochromic properties in one of the components.

Novel Smart Microreactors Equipped with Responsive Catalytic Nanoparticles on Microchannels

Nowadays efficient and reliable control of highly exothermic reactions to effectively prevent overheating or even explosions still remains a challenging task, although newly developed microreactor technology has shown promise. Here, we report a novel smart microreactor system equipped with responsive catalytic nanoparticles on microchannels for self-regulated control over highly exothermic reactions by responding to the reaction-generated heat. On the basis of shrinking/swelling behaviors of polymeric networks in the responsive catalytic nanoparticles, the smart microreactor could respond to the change of reaction temperature to tune the catalysis activity of catalytic particles in a thermo-feedback process. As a breakthrough result, highly exothermic reactions carried out in such a microreactor can be well-controlled in a self-regulation process without any manual assistance, efficiently ensuring the safety of the reaction. Such smart responsive catalytic systems have high potential and are attractive as a new generation of efficient tools that feature a self-regulation property for highly exothermic catalytic reactions.

Harnessing the Versatility of Continuous-Flow Processes: Selective and Efficient Reactions

There is a great need for effective transformations and a broad range of novel chemical entities. Continuous-flow (CF) approaches are of considerable current interest: highly efficient and selective reactions can be performed in CF reactors. The reaction setup of CF reactors offers a wide variety of possible points where versatility can be introduced. This article presents a number of selective and highly efficient gas-liquid-solid and liquid-solid reactions involving a range of reagents and immobilized catalysts. Enantioselective transformations through catalytic hydrogenation and organocatalytic reactions are included, and isotopically labelled compounds and pharmaceutically relevant 1,2,3-triazoles are synthesized in CF reactors. Importantly, the catalyst bed can be changed to a solid-phase peptide synthesis resin, with which peptide synthesis can be performed with the utilization of only 1.5 equivalents of the amino acid.

Switching between intermolecular and intramolecular reactions using flow microreactors: lithiation of 2-bromo-2′-silylbiphenyls

Switching between the intermolecular reaction and the intramolecular reaction was achieved at will using flow microreactors.

The past, present and potential for microfluidic reactor technology in chemical synthesis

The past two decades have seen far-reaching progress in the development of microfluidic systems for use in the chemical and biological sciences. Here we assess the utility of microfluidic reactor technology as a tool in chemical synthesis in both academic research and industrial applications. We highlight the successes and failures of past research in the field and provide a catalogue of chemistries performed in a microfluidic reactor. We then assess the current roadblocks hindering the widespread use of microfluidic reactors from the perspectives of both synthetic chemistry and industrial application. Finally, we set out seven challenges that we hope will inspire future research in this field.

Practical synthesis of photochromic diarylethenes in integrated flow microreactor systems

An effective method for the synthesis of photochromic diarylethenes through the generation of heteroaryllithiums and subsequent reaction with octafluorocyclopentene has been developed by using integrated flow microreactor systems. Reactions can be conducted without using cryogenic conditions by virtue of effective temperature and residence time control, although much lower temperatures (<-78 °C) are needed for batch macroreactions. Moreover, the synthesis of unsymmetrical diarylethenes, which is difficult to achieve when using conventional batch macrosystems, has been accomplished based on the selective introduction of one aryl group to give arylheptafluorocyclopentene followed by the introduction of another aryl group. The productivity of the laboratory-scale system is approximately 0.5 mmol min(-1). Therefore, the present integrated flow microreactor method serves as a practical way of synthesizing various photochromic diarylethene derivatives.