In order to investigate the influence of polymer aggregate state and chemical environment on the fluorescent performance of nanocrystal

monodisperse CdS nanocrystal is prepared via liquid-solid-solution synthesis (LSS) strategy

and monodisperse CdS nanocrystals/poly(N-isopropylacrylamide) (PNIPAM) complex hydrogel are prepared by radical polymerization.The microstructure and performance of the monodisperse CdS nanocrystal and the complexes hydrogel are characterized by high resolution transmission electron microscopy (HRTEM)

X-ray diffraction (XRD)

Fourier transformed infrared spectroscopy (FTIR)

differential scanning calorimetry (DSC) and photoluminescence (PL).As evidenced from the HRTEM photos and XRD patterns

CdS nanocrystals show well monodispersity

and their size is about 2.8 nm.PL spectrum shows that CdS nanocrystal has a strong emitting peak around 533 nm and a weak emitting peak around 469 nm.DSC curves suggest that the complex hydrogel is thermosensitive

and LCST of which is higher than that of PNIPAM hydrogel.The results of PL spectra and DSC curves indicate that the complex hydrogel shows well thermosensitive-fluorescent performance

the variation of the fluorescent intensity of the complex hydrogel is in good agreement with its phase transformation.With variation of environmental temperature from 20℃ to 45℃

the complex hydrogel changes from swollen state to collapse state

and the chemical environment around CdS nanocrystal changes from hydrophilic to hydrophobic

quantum yield of CdS nanocrystal changes respectively.The lower the environmental temperature is kept

the lower fluorescent intensity of the complex hydrogel is observed

and the fluorescent intensity changes sharply around its LCST.Testing on PL intensity change of CdS/PNIPAM hydrogel as a function of cooling-heating cycles between 20℃ and 40℃ demonstrates that the thermosensitive-fluorescent performance of the CdS/PNIPAM hydrogel is reversible.