Spiropyran-modified silicon quantum dots (Si QDs) were successfully fabricated through covalently linking the aminated Si QDs and spiropyrans. In comparison with Si QDs, the fluorescence emission peaks of the Si QDs in the spiropyran-modified Si QDs always locate at 525 nm irrespective of the excitation wavelengths. The spiropyran-modified Si QDs showed reversible photoluminescence. Blue-green fluorescence of the spiropyran-modified Si QDs could be gradually switched off, and red fluorescence could be gradually switched on with UV irradiation. The process could be reversible with visible light irradiation. The reversibly switchable photoluminescence of the spiropyran-modified Si QDs using UV and visible light irradiation could also be multiply repeated with good stability. Therefore, the spiropyran-modified Si QDs could be a promising candidate in many potential application areas such as photo-switch, data storage, and biolabeling and bioimaging.

A kind of photoswitchable nanoparticles which are the fluorescent carbon nanoparticles grafted with the copolymers of styrene and spiropyran (f-CNP-g-poly(St-co-SP) is reported. The f-CNP-g-poly(St-co-SP) not only feature the reversibly photoswitchable fluorescence, but also have good processability. Their fluorescence could be reversibly switched between blue-green and red by using ultraviolet/visible light irradiation. Furthermore, they could be readily processed into nanofibers with reversibly photoswitchable fluorescence by electrospinning. They can be potentially applied in fabricating microdevice, optical switching, information storage, anti-counterfeiting as well as biological imaging.

Fluorescent carbon nanoparticles (f-CNPs) were grafted with polystyrene using a “grafting from” method via atom transfer radical polymerization. The fluorescent carbon nanoparticles grafted with polystyrene (f-CNP-g-PSt) were characterized using nuclear magnetic resonance, Fourier transform infrared spectroscopy, transmission electron microscopy, gel permeation chromatography, dynamic light scattering and fluorescence spectroscopy. The synthesized f-CNP-g-PSt are fluorescent in solution or in the solid state with the appropriate excitation wavelength and exhibit better dispersibility and processability compared to f-CNPs.

Fluorescent carbon nanoparticles (CNPs) with diameters of about 3 nm which can emit blue-green light were synthesized through the hydrothermal carbonization of ethylenediaminetetraacetic acid disodium salt (EDTA·2Na). Then, the CNPs were functionalized with spiropyrans to obtain the spiropyran-functionalized CNPs. The emission of the spiropyran-functionalized CNPs centered at 510 nm could be switched off, while being turned on at 650 nm via energy transfer after UV light irradiation. The process could be reversed by using visible light irradiation. The optical switching of the fluorescence was repeated 10 times without apparent “fatigue”, showing excellent photoreversibility and high stability. Spiropyran-functionalized CNPs may find potential applications in biological imaging and labeling, reversible data storage/erasing, as well as individual light-dependent nanoscale devices.

The light-controlled fluorescence molecular switch was prepared with Au nanoclusters and thiolated spiropyran dyes. Its fluorescence can be reversibly modulated using UV/Visible light due to fluorescence resonance energy transfer (FRET) from the Au NCs to the open-ring state merocyanine of the spiropyran molecules.

The light-controlled fluorescence molecular switch was prepared with Au nanoclusters and thiolated spiropyran dyes. Its fluorescence can be reversibly modulated using UV/Visible light due to fluorescence resonance energy transfer (FRET) from the Au NCs to the open-ring state merocyanine of the spiropyran molecules.

Fluorescent carbon nanoparticles (CNPs) with diameters of about 3 nm which can emit blue-green light were synthesized through the hydrothermal carbonization of ethylenediaminetetraacetic acid disodium salt (EDTA·2Na). Then, the CNPs were functionalized with spiropyrans to obtain the spiropyran-functionalized CNPs. The emission of the spiropyran-functionalized CNPs centered at 510 nm could be switched off, while being turned on at 650 nm via energy transfer after UV light irradiation. The process could be reversed by using visible light irradiation. The optical switching of the fluorescence was repeated 10 times without apparent “fatigue”, showing excellent photoreversibility and high stability. Spiropyran-functionalized CNPs may find potential applications in biological imaging and labeling, reversible data storage/erasing, as well as individual light-dependent nanoscale devices.