Renlu Han

pH-Responsive drug release and NIR-triggered singlet oxygen generation based on a multifunctional core–shell–shell structure

A multifunctional platform with pH-responsive drug release and near-infrared (NIR) light-triggered photodynamic therapy (PDT) was designed and prepared using the novel core-shell-shell structure. The multifunctional platform consists of an upconversion nanoparticle (UCNP) emission core, a photosensitizer methylene blue (MB) embedded dense silica sandwich shell, and a polyethyleneimine conjugated folic acid (PEI-FA) gated mesoporous silica (MS) outmost shell with doxorubicin hydrochloride (DOX) loaded inside. The simulated drug release experiments revealed that DOX will release from the nanoparticles because of the distortion in the PEI-FA layer under acidic conditions. Moreover, under 980 nm NIR irradiation, a 660 nm red light emission was excited, activating MB to generate a singlet oxygen (1O2), which acts as the PDT drug. The multifunctional platform integrated pH-responsive drug release and UCNP-based PDT drug together show promising potential in nanomedicine for future chemotherapy and NIR-triggered PDT.

Triple-doped KMnF3:Yb3+/Er3+/Tm3+ nanocubes: four-color upconversion emissions with strong red and near-infrared bands.

Triple-doped (Yb3+/Er3+/Tm3+) KMnF3 nanocubes with uniform sizes of 250 nm were synthesized by a facile hydrothermal route using the oleic acid as the capping agent. It was found that these nanocubes can simultaneously exhibited four-color (blue, green, red and NIR) upconversion emissions under a single 980 nm near-infrared (NIR) laser excitation, which should have potential multicolor in vivo imaging applications. Specifically, the red (660 nm) and NIR (800 nm) peaks, known as two “optical windows” for imaging biological tissues, were strong. The spectral and pump analyses indicated the two-photon processes were responsible for the both red and NIR emissions.

Negative Capacitance in BaTiO3/BiFeO3 Bilayer Capacitors

Negative capacitances provide an approach to reduce heat generations in field-effect transistors during the switch processes, which contributes to further miniaturization of the conventional integrated circuits. Although there are many studies about negative capacitances using ferroelectric materials, the direct observation of stable ferroelectric negative capacitances has rarely been reported. Here, we put forward a dc bias assistant model in bilayer capacitors, where one ferroelectric layer with large dielectric constant and the other ferroelectric layer with small dielectric constant are needed. Negative capacitances can be obtained when external dc bias electric fields are larger than a critical value. Based on the model, BaTiO3/BiFeO3 bilayer capacitors are chosen as study objects, and negative capacitances are observed directly. Additionally, the upward self-polarization effect in the ferroelectric layer reduces the critical electric field, which may provide a method for realizing zero and/or small dc bias assistant negative capacitances.