is attributed to the variations of

is attributed to the variations of the solution properties by the addition of the PCM and luminescence into the PVP solution.
The energy dispersive spectra reveal the presence of Eu, C, O, and N elements in PVP/Eu-PEG nanofibers. The elements of Au and Pd in the spectra come from the Au–Pd film coated on the surface of the sample for SEM observation.
DSC curves acquired from heating electrospun PVP/Eu-PEG fibers are shown in Fig. 3; the melting temperature (Tm) and enthalpy of melting (ΔHm) are listed in Table 1. The phase transition temperatures were recorded as the maximum values of the DSC curves. The phase- change temperature range of the PVP/Eu-PEG composite fibers is 59– 65 1C, while that of PEG powder is 55–67 1C, which indicates that PVP has no remarkable effect on the phase-change temperatures of PCMs in the composite fibers, and its enthalpy increased with increasing PEG molecular weight. The emission spectra of PVP/Eu-PEG with PEG2000 are shown in Fig. 4. The Eu complex was excited up to an optimum excitation wave length of 293 nm to obtain the featured fluorescence spectra. The PVP/ Eu-PEG spectra show that the Eu complex has excellent luminescent properties. All fluorescence emission peaks of the complex with Eu3þ are from the 5D0–7FJ (J¼1–4) transition of Eu3þ. In the emission spectrum of PVP/Eu-PEG with PEG 2000, the corresponding emission peaks based on the 5D0–7F1 (592 nm), 5D0–7F2 (615 nm) 5D0–7F3