The Influence of Rare Earth Ions on the Rheological Behavior of Polyamide

The polyamide 66 （PA66）/lanthanum acetate blends with small amounts of salt loadings （≤ 1 wt% of PA） have been prepared in a twin-screw extruder. The rheology of PA66 and its blends has been investigated by a rotational rheometer. The results suggested that with the salt loading in excess of 0.2 wt% the typical Newtonian viscosity plateau disappeared and both the low-frequency complex viscosities η^＊ and storage modulus G＇ of blends were much higher than those of neat PA66, the storage modulus was higher than the loss modulus at low frequencies （tanδ〈 1）, i.e., the melt changed from a viscoelastic liquid for unfilled polymer to a viscoelastic solid （G′ 〉 G″）. While the viscosity followed a strong shear thinning with increasing frequency, the η^＊ and G′ decreased significantly even lower than those of neat PA66 at high frequencies. The combination of dynamic mechanical analysis （DMA） and X-ray photoelectron spectroscopy （XPS） analysis has revealed that coordination effect occurred between lanthanum and carbonyl oxygen atoms in amide groups of the polymer to form pseudo- crosslinked network structure, which makes the glass transition temperatures （Tg） and storage modulus （E′） of blends enhanced. The network structure formation-destruction and chains entanglement-disentanglement processes at different frequencies are responsible for the above rheological behaviors of blends.

Theranostic gold cluster nanoassembly for simultaneous enhanced cancer imaging and photodynamic therapy

As one of near-infrared（NIR） fluorescent（FL） nanoprobes, gold nanoclusters（Au NCs） are delicated to passive-targeting tumors for NIR FL imaging, but which easily cleared by the kidneys for the small size（〈1.5 nm）. Herein, the well-defined gold clusters nanoassembly（Au CNA） was synthesized by the selfassembly of Au NCs based on protein cross-linking approach. The as-prepared Au CNA demonstrated highly effective cellular uptake and precise tumor targeting compared to that of Au NCs. Moreover, with the irradiation of 660 nm laser, Au CNA generated largely reactive oxygen species（ROS） for photodynamic therapy（PDT）. In vitro and [39TD$IF]in vivo PDT revealed that Au CNA exhibited largely cell death and significantly tumor removal at a low power density of 0.2 W/cm^2. It could be speculated that the laser-excited Au CNA produced photon energy, which further obtained electron from oxygen to generate radical species.Therefore, Au CNA as a photosensitizer could realize NIR FL imaging and NIR laser induced PDT.