Brush polymers PHEMA-g-(PCL-b-PEG) with poly(2-hydroxyethyl methacrylate) (PHEMA) as the backbone and poly(epsilon-caprolactone)-b-poly(ethylene glycol) (PCL-b-PEG) block copolymers as side chains were synthesized and evaluated as drug delivery vehicles. Two brush polymers were synthesized, and their structures were confirmed by gel permeation chromatography analyses and (1)H NMR measurements. The brush polymers self-assembled into micelles in aqueous solution, and the critical micellization concentrations of brush polymers were 2-fold lower than that of the linear diblock copolymer PCL-b-PEG with structure similar to that of the grafted side chains of brush polymers, indicating the higher aqueous stability of brush polymer micelles. The micelles were spherical with average diameters below 100 nm. Brush polymer micelles exhibited higher loading doxorubicin capacity compared with micelles from linear PCL-b-PEG block copolymer by the dialysis method, and the burst doxorubicin release from the brush polymer micelles was significantly suppressed. Doxorubicin-loaded brush polymer micelles can be effectively internalized by A549 human lung carcinoma cells and slowly released the encapsulated drug molecules as demonstrated by the drug accumulation in cytoplasm, which was opposite to free doxorubicin, which accumulated rapidly in the cell nuclei.
Flexible pressure sensors are attracting great interest from researchers and are widely applied in various new electronic equipment because of their distinct characteristics with high flexibility, high sensitivity, and light weight; examples include electronic skin (E-skin) and wearable flexible sensing devices. This review summarizes the research progress of flexible pressure sensors, including three kinds of transduction mechanisms and their respective research developments, and applications in the fields of E-skin and wearable devices. Furthermore, the challenges and development trends of E-skin and wearable flexible sensors are also briefly discussed. Challenges of developing high extensibility, high sensitivity, and flexible multi-function equipment still exist at present. Exploring new sensing mechanisms, seeking new functional materials, and developing novel integration technology of flexible devices will be the key directions in the sensors field in future.
Electrocatalytic nitrogen reduction reaction (NRR) has been an important area for many scientists. However, high voltage requirements, low NH3 yield, and poor stability remain the biggest challenges for NRR. Here, novel high‐entropy alloys RuFeCoNiCu nanoparticles with small size (≈16 nm) and uniformity, prepared in oil phase at atmospheric pressure and low temperature (≤250 °C) are reported for the first time and are applied to NRR. According to the experiments, there is a high NH3 yield at a low overpotential. It has a surprising NH3 yield of 57.1 µg h–1 mgcat−1 (11.4 µg h–1 cm–2) at 0.05 V versus RHE in 0.1 m KOH, and the corresponding Faradaic efficiency reaches 38.5%, which is the electrocatalyst with the highest NH3 yield at the voltage of 0.05 V versus RHE reported so far. Similarly, the material also exhibits excellent electrochemical properties in other electrolytes such as 0.1 m Li2SO4, 0.1 m Na2SO4, and 0.1 m HCl electrolytes. Besides, after the 100 h test, only slightly diminished in activity. Theoretical calculation shows that Fe surrounded by alloy metals is the best site for N2 adsorption and activation. Co‐Cu and Ni‐Ru couples show an excellent capacity to surface hydrogenation at a low overpotential.
Although intensive efforts have been made and great progress has been achieved relating to the electrocatalytic hydrogen evolution reaction (HER), an advanced synthesis strategy for an efficient electrocatalyst is still the most significant goal.
Sulfur nanodots (S-dots), composed of elemental sulfur core and surface ligands, show unexpected photoluminescence (PL) properties, with the unique features of nontoxicity, hydrophilicity, high stability and easy of modification. This...
W18O49@PDMS mesocrystal membrane with the hydrophobic top and the hydrophilic bottom possesses the properties of self-floating and water transportation simultaneously.
Photosensitive surfaces treated to have in-plane structural anisotropy by illumination with polarized light can be used to orient liquid crystals (LCs). Here we report a detailed study of the dynamic behavior of this process at both short and long times, comparing the ordering induced in the bare active surface with that of the LC in contact with the surface using a high-sensitivity polarimeter that enables detailed characterization of the anisotropy of the active surface. The experiments were carried out using self-assembled monolayers (SAMs) made from dimethylaminoazobenzene covalently bonded to a glass surface through a triethoxysilane terminus. This surface gives planar alignment of the liquid crystal director with an azimuthal orientation that can be controlled by the polarization of actinic light. We find a remarkable long-term collective interaction between the orientationally ordered SAM and the director field of the LC: while an azobenzene based SAM in contact with an isotropic gas or liquid relaxes to an azimuthally isotropic state in the absence of light due to thermal fluctuations, an orientationally written SAM in contact with LC in the absence of light can maintain the LC director twist permanently, that is, the SAM is capable of providing azimuthal anchoring to the LC even in the presence of a torque about the surface normal. We find that the short-time, transient LC reorientation is limited by the weak azimuthal anchoring strength of the SAM and by the LC viscosity.
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