Rational Design of Surface-State Controlled Multicolor Cross-Linked Carbon Dots with Distinct Photoluminescence and Cellular Uptake Properties.

We disclose for the first time a facile synthetic methodology for the preparation of multicolor carbon dots (CDs) from a single source barring any chromatographic separations. This was achieved via sequential intraparticle cross-linking of surface abundant carboxylic acid groups on the CDs synthesized from a precursor to control their photoluminescence (PL) spectra as well as affect their degree of cellular internalization in cancer cells. The change in PL spectra with sequential cross-linking was projected by theoretical density functional theory (DFT) studies and validated by multiple characterization tools such as X-ray photoelectron spectroscopy (XPS), PL spectroscopy, ninhydrin assay, etc. The variation in cellular internalization of these cross-linked CDs was demonstrated using inhibitor assays, confocal microscopy, and flow cytometry. We supplemented our findings with high-resolution dark-field imaging to visualize and confirm the colocalization of these CDs into distinct intracellular compartments. Finally, to prove the surface-state controlled PL mechanisms of these cross-linked CDs, we fabricated a triple-channel sensor array for the identification of different analytes including metal ions and biologically relevant proteins.

Dopamine Delivery via pH-Sensitive Nanoparticles for Tumor Blood Vessel Normalization and an Improved Effect of Cancer Chemotherapeutic Drugs.

Tumor blood vessels have been reported to be abnormal in both structure and function compared with those in normal tissues, leading to a hostile microenvironment and inadequate antitumor drug delivery. Dopamine, a chemical messenger, is proven to inhibit angiogenesis and improve tumor vessel normalization. Here, a mesoporous silicon nanoparticle (MSN) is constructed that is responsive to the weakly acidic pH of the tumor extracellular matrix for steady delivery and tumor-localized release of dopamine. Then MSNs are functionalized with amine conjugated phenylboronicacid molecules, and dopamine is loaded by reacting with phenylboronic acid. In a weakly acidic environment, MSNs intelligently release dopamine due to the hydrolysis of boronic-ester bond between dopamine and phenylboronic acid, resulting in an evident inhibition of vascular endothelial cell migration and tubule formation. It is shown that loading of dopamine into the functional MSNs significantly prolong the circulatory half-life of this small molecule. After intravenous injection to tumor bearing mice, this nanoformulation induce tumor blood vessel normalization, thereby improving the antitumor chemotherapeutic efficacy of doxorubicin. This study demonstrates that the pH-responsive MSN offers great potential for delivery of dopamine in vivo and the normalization of tumor vessels by dopamine can provide an auxiliary treatment for cancer chemotherapeutic drugs.

Detecting electronic structure evolution of semiconductor nanocrystals by magnetic circular dichroism spectroscopy.

The evolution of electronic states of nanocrystals under shape variation is hardly detected by conventional optical and electronic instruments due to the condensed electronic levels of nanocrystals. Herein, we demonstrate that magnetic circular dichroism (MCD) spectroscopy is a high-resolution method to monitor this delicate progress on account of the sensitive Zeeman response to electronic states. In particular, the MCD intensity of the first excitonic transition exponentially decreases with the shape changing from quantum dots to quantum rods owing to the increased density of valence pz state with elongation in the z direction, which contributes much less to MCD intensity compared with p±. This work provides a simple but effective strategy for understanding the electronic state evolution in various semiconductor nanomaterials.

MOF-derived nitrogen-doped nanoporous carbon for electroreduction of CO2 to CO: the calcining temperature effect and the mechanism.

Nitrogen-doped carbon materials are promising electrocatalysts for electroreduction of CO2. However, the low current density and moderate faradaic efficiency of these materials limit their practical application. Here, we report the MOF-derived nitrogen-doped nanoporous carbon (NC) as a highly efficient and stable electrocatalyst for the conversion of CO2 to CO. The NC catalysts were prepared by calcining ZIF-8 at different temperatures in argon (Ar). The catalytic performances show that the higher pyrolysis temperature result in a better CO2 electroreduction activity of the catalysts. The NC catalyst with the best performance achieves high selectivity with 95.4% CO faradaic efficiency (FE) at -0.5 V vs. reversible hydrogen electrode (RHE). The catalyst also maintains long-term stability of 20 h operation, after which the FE of CO is still greater than 90%. The experiments show that higher pyrolysis temperature reduces the total nitrogen (N) but changes the nature and density of N defects. Density functional theory calculations reveal that higher pyrolysis temperature leads to enhanced activity by promoting the formation of low multiple pyridinic N, which provides more efficient active sites.