We report on the fabrication of hybrid silica nanoparticles densely grafted with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) brushes with inner and outer layers selectively labeled with fluorescence resonance energy transfer (FRET) donors, 4-(2-acryloyloxyethylamino)-7-nitro-2,1,3benzoxadiazole (NBDAE), and photoswitchable acceptors, 1 0 -(2-methacryloxyethyl)-3 0 ,3 0 -dimethyl-6-nitro-spiro(2H-1-benzo-pyran-2,2 0 -indoline) (SPMA), respectively, via surface-initiated sequential atom transfer radical polymerization (ATRP). P(NIPAM-co-NBDAE)-b-P(NIPAM-co-SPMA) brushes at the surface of silica core exhibit collapse in the broad temperature range of 20-37 °C. UV irradiation of the aqueous dispersion of hybrid silica nanoparticles induces the transformation of SPMA moieties in the outer layer of polymer brushes from nonfluorescent spiropyran (SP) form to fluorescent merocyanine (MC) form, leading to occurrence of the FRET process between NBDAE and SPMA residues. Most importantly, the FRET efficiency can be facilely tuned via thermoinduced collapse/swelling of P(NIPAM-co-NBDAE)-b-P(NIPAM-co-SPMA) brushes by changing the relative distance between donor and acceptor species located within the inner and outer layers of polymer brushes, respectively. Thus, hybrid silica nanoparticles coated with P(NIPAM-co-NBDAE)-b-P(NIPAM-co-SPMA) brushes can serve as a sensitive ratiometric fluorescent thermometer. On the other hand, when the hybrid nanoparticle dispersion was irradiated with visible light again after UV irradiation, the MC form of SPMA moieties reverts back to the nonfluorescent SP form, leading to the turn-off of FRET process. Overall, aqueous dispersion of this novel type of hybrid silica nanoparticle is capable of emitting multicolor fluorescence, which can be facilely tuned by UV irradiation, visible light, and temperatures or a proper combination of these factors.

Superchiral light, generated by the interference of two counter-propagating circularly polarized light (CPL) with same frequency, opposite handedness and different intensity, exhibits enhanced dissymmetry in its interaction with chiral molecules, and has the potential for ultrasensitive detection and characterization of chiral molecules. It is anticipated that the enhanced optical dissymmetry in superchiral light (SCL) field may be utilized to promote asymmetric photochemical reactions efficiency. Herein we reported SCL impart greater chiral bias to trigger asymmetric photo-polymerization reaction from initially achiral diacetylene (DA) monomer, and the enhanced optical dissymmetry for whole polydiacetylene (PDA) films could be achieved. An explanation based on the chiral transfer and amplification of chiral bias from SCL during the polymerization process has been proposed. Moreover, thus formed chiral PDA films polymerized by SCL exhibited enhanced enantioselective recognition ability, and can serve as a direct visual probe for the discrimination of some specific enantiomers.

We report herein the development of a highly robust, quantitative, sensitive, and naked eye colorimetric detection method for different isomers of aromatic compounds using β-CD-modified silver nanoparticle (AgNPs) probes. This assay relies on the distance-dependent optical properties of Ag nanoparticles and the different inclusion binding strength of the aromatic guests to β-CD host. In the presence of different isomers of aromatic compounds, AgNPs could be rapidly induced to aggregate, thereby resulting in apricot-to-red color change. The variety and concentration of different isomers of aromatic compounds could be determined by monitoring with the naked eye or a UV-vis spectrometer. The present detection limit for different isomers of aromatic compounds is 5 × 10(-5) M. We believe that the surface architectures of AgNPs after the introduction of the CD-based host-guest recognition would be applicable for a range of chemical and bioanalytical molecular sensing systems in aqueous media.

By introducing methanol as a co-solvent into cyclopentanone, solvent effects on structure, photoresponse and speed of gelation of a dicholesterol-linked azobenzene organogel DCAZO2 have been investigated. Optical microscopy (OM) and scanning electron microscopy (SEM) images reveal that the gel fibers form macroscopic aggregates by adding methanol. Minimum gelation concentration (MGC) of the gels decreases with increasing methanol content, while the gel-to-sol transition temperature (T gel ) decreases firstly and increases afterwards. For photoisomerization (corresponding to gel-sol transition), the first stage rate constant k g1 of the gels decreases with increasing methanol content. The photoisomerization process of the gel with 5% methanol is different from the other five samples, whose first stage rate constant k g1 is greater than its second stage rate constant k g2 . By increasing methanol content from 0% to 30%, gelation time (corresponding to sol-gel transition) of both heated gel and UV-visible light irradiated gel decreases from 7 h to 5 min and 6 h to 0 min (before visible light irradiation is accomplished), respectively. Solubility parameters and Teas plots of the gelator and mixed solvents are systematically calculated to estimate the gelator-solvent interaction. It is found that gelation requires that the gelator-solvent interaction be neither too strong nor too weak, otherwise solution or precipitate are formed.

We demonstrate the realization of a coherent random fiber laser (RFL) in the extremely weakly scattering regime, which contains a dispersive solution of polyhedral oligomeric silsesquioxanes nanoparticles (NPs) and laser dye pyrromethene 597 in carbon disulfide that was injected into a hollow optical fiber. Multiple scattering of polyhedral oligomeric silsesquioxanes NPs greatly enhanced by the waveguide confinement effect was experimentally verified to account for coherent lasing observed in our RFL system. This Letter extends the NPs-based RFLs from the incoherent regime to the coherent regime.

Magnetic optical activity, which can occur in all media and is induced by longitudinal magnetic field, causes the difference in absorption coefficients of left and right circularly polarized light and has the potential for magnetically induced enantioselectivity in chemical reactions. Compared with the well-established technique with circularly polarized light, there are few reports on the production of helical conjugated polymers in a photochemical reaction based on above magnetochiral anisotropy mechanism. Herein, we demonstrate experimentally that the enantioselective polymerization of diacetylene derivative can be achieved in the liquid crystal phase by application of linearly polarized light under a parallel or antiparallel magnetic field. The screw direction of predominant helical polydiacetylene chain can be rigorously controlled with the relative orientation of linearly polarized light and the magnetic field. Moreover, the prepared helical polydiacetylene assemblies can serve as a direct visual probe for the enantioselective recognition of D-or L-lysine.

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Herein, photo-controlled inclusion and exclusion reaction of azobenzene-containing polydiacetylene vesicles with alpha-cyclodextrin were used to act as driving force to induce chromatic transition of PDA vesicles, which provided a novel model system that combines photochemistry and host-guest chemistry for a photo-stimulus-responsive vesicle.