Adsorption and release on three-dimensional graphene oxide network structures

In this study, three-dimensional network architectures are constructed using nano-sized graphene oxide (nGO) as the building block. The cross-linking reaction of nGO is conducted in sub-micrometre water droplets in an emulsion system to control the size of the networks by restricting the reaction space. Two types of three-dimensional GO networks with different cross-linking lengths were constructed, and their methyl orange adsorption and release behaviours were investigated under external stimuli, such as thermal treatment, ultrasonic wave treatment and near-infrared light irradiation

Photochemical OFF/ON Cytotoxicity Switching by Using a Photochromic Surfactant with Visible Light Irradiation

Photochemical switching of cytotoxicity by using spiropyran compounds with pyridinium and alkyl groups was investigated. The spiropyran compound, SP6, with a hexyl group as the alkyl group displayed negative photochromism, in which the hydrophilic open merocyanine form (MC form) was stable and isomerized to the hydrophobic closed spiro form (SP form) by visible light irradiation. Both MC and SP forms exhibited amphiphilicity because of the hydrophobic hexyl and hydrophilic pyridinium groups introduced. Cytotoxicity toward HeLa cells was observed for both MC and SP forms of SP6 at concentrations higher than the critical aggregation concentration of the isomers CACMC and CACSP (CACMC > CACSP), respectively. In contrast, cytotoxicity by SP6 was activated by visible light irradiation at concentrations between CACMC and CACSP; thus, photochemical switching of cytotoxicity from the OFF to ON state was achieved. Cytotoxicity was revealed to be caused by disruption of the cell membrane. The results provide an important step in developing novel next-generation photochemotherapy drugs

Fluorescence photoswitching based on a photochromic pKa change in an aqueous solution

Reversible fluorescence photoswitching of RSA-AZO dyad 1 was clearly demonstrated in an acidic aqueous solution. The fluorescence photoswitching mechanism is based on the reversible ring opening/closing reactions of RSA unit induced by a photochromic pKa change along with the photoisomerization of AZO unit

A photochromic ATP analogue driving a motor protein with reversible light-controlled motility: controlling velocity and binding manner of a kinesin–microtubule system in an in vitro motility assay

We synthesized two photochromic ATP analogues (ATP-Azos) featuring azobenzene derivatives tethered at the 2′ position of the ribose ring. In the presence of the ATP-Azo tethering p-tert-butylazobenzene, we observed reversible photo-control of the motility, velocity and binding manner, of a kinesin–microtubule system in an in vitro motility assay

Photochromism of a diarylethene derivative in aqueous solution capping with a water-soluble nano-cavitand

A photochromic diarylethene, 1,2-bis(3-methyl-2-thienyl)perfluorocyclopentene (1) was encapsulated into water-soluble nano-cavitand 2 to induce the photochromic performance in aqueous solution. H-1 NMR measurements confirmed the formation of 1:1 complex between 1 and 2 in a D2O solution. Upon irradiation with UV and visible light, encapsulated diarylethene within nano-cavitand exhibited reversible and efficient photochromic reactions even in the aqueous solution. The photocyclization and photocycloreversion quantum yields are almost similar to those observed in organic solvents. The efficient photochromic performance of the diarylethene in aqueous solution is attributed to that the empty pore of 2 selectively captures the hydrophobic perfluorocyclopentene moiety and the reactive thiophene moieties are free from the cavity, as evidenced by H-1 NOESY measurement

Photochromic fluorophores at the molecular and nanoparticle levels: fundamentals and applications of diarylethenes

International audienceFluorescent molecules and materials are widely used in many areas in physics, chemistry, and biology as emitters, tags, or sensors. The possibility of controlling their fluorescence signal by light, namely, fluorescence photoswitching, down to the nanoscale level can then dramatically extend their fields of applications. This review focuses on fluorescent and photochromic diarylethene-based nanosystems. The choice of the diarylethene family has been driven by its excellent photoswitching properties (conversion yield, bistability, fatigue resistance), which make them fully appropriate when high-performance behavior is required. The different molecular and nanomaterial designs providing suitable combinations of fluorescence and photochromism are summarized. Besides the inherently fluorescent diarylethene molecules, chemical association between photochromic and fluorescent molecular units can advantageously lead to fluorescence photoswitching thanks to resonance energy transfer or intramolecular electron transfer processes. Furthermore, the preparation of nanoscale emissive materials involving diarylethene units paves the way to new interesting features, such as near-infrared control of emissive and photoswitchable nanohybrids, giant amplification of the fluorescence photoswitching in organic nanoparticles, or fluorescence color modulation. Many applications derived from such fluorescent diarylethene-based molecules and nanomaterials have been developed recently, especially in the field of biology for fluorescence biolabeling and super-resolution imaging but also for photocontrol of biological functions. Extremely promising prospects are expected in the near future