MRI Contrast Agents Based on Conjugated Polyelectrolytes and Dendritic Polymers.

Three complexes of gadolinium-based on dentritic molecules are reported as magnetic resonance imaging (MRI) contrast agents. Their ligands feature four carboxylate groups, which contribute to good water solubility and a strong combination with metal ions. As a new attempt, coupling polymerization is carried out to make a combination of conjugated polyelectrolytes and dendrimers for MRI contrast agents. For comparison, mononuclear and binuclear complexes are also reported. The investigation suggests that the contrast agent with the newly designed macromolecular skeleton provides higher longitudinal relaxivity value (36.2 mm -1 s-1 ) and more visible enhancement in in vivo and in vitro MR images than the small molecular ones. In addition, extremely low cytotoxicity and main clearance via hepatobiliary are confirmed, which reduces the deterioration of chronic kidney disease. All the results indicate that these three complexes are generally applicable as promising clinical contrast agents.

Selectivity of quantum dot sensitized ZnO nanotube arrays for improved photocatalytic activity.

In this work, PbS/ZnO, CdS/ZnO and CdSe/ZnO hierarchical heterostructures have been successfully synthesized by combining water bath and chemical bath deposition (CBD) methods on indium-doped tin oxide (ITO). Scanning electron microscopy (SEM) results show that quantum dots (QDs) certainly form on the pre-grown ZnO nanorod (NR) and nanotube (NT) arrays. The amount of QDs capped on ZnO could be regulated by varying the cycle times. The photocatalytic activity of the QD-sensitized ZnO is investigated by decomposition of methyl orange (MO) under irradiation, which show remarkable enhancement compared to bare ZnO. The ZnO NTs sensitized by PbS QDs have the highest catalytic activity among the three QDs (PbS, CdS and CdSe QDs). The UV-vis absorption diagrams and the Ct/C0 curves reveal that 8PbS/ZnO NTs have the highest catalytic activity, which can degrade MO (20 mg L-1) into a colorless solution within 30 min. Meanwhile, the synthetic methodology described herein provides an effective approach for fabricating a variety of photocatalysts. The heterostructured nanomaterials have significant potential to solve environmental and energy issues.

Short-Time Hydrothermal Synthesis of CuBi2O4 Nanocolumn Arrays for Efficient Visible-Light Photocatalysis.

In this article, a short-time hydrothermal method is developed to prepare CuBi2O4 nanocolumn arrays. By using Bi(NO3)3·5H2O in acetic acid and Cu(NO3)2·3H2O in ethanol as precursor solutions, tetragonal CuBi2O4 with good visible light absorption can be fabricated within 0.5 h at 120 °C. Tetragonal structured CuBi2O4 can be formed after 15 min hydrothermal treatment, however it possesses poor visible light absorption and low photocatalytic activity. Extending the hydrothermal treatment duration to 0.5 h results in a significant improvement invisible light absorption of the tetragonal CuBi2O4. The CuBi2O4 obtained through 0.5 h hydrothermal synthesis shows a band gap of 1.75 eV and exhibits the highest photocatalytic performance among the CuBi2O4 prepared with various hydrothermal time. The removal rate of methylene blue by the 0.5 h CuBi2O4 reaches 91% under visible light irradiation for 0.5 h. This study proposes a novel strategy to prepare photoactive CuBi2O4 nanocolumn arrays within 0.5 h at a moderate temperature of 120 °C. The hydrothermal method provides a facile strategy for the fast synthesis of metal-oxide-based photocatalysts at mild reaction conditions.

Atomic-scale engineering of MOF array confined Au nanoclusters for enhanced heterogeneous catalysis.

A surface-engineered heterogeneous catalyst with a controllable catalytic interface is the most straightforward approach for boosting catalytic activity. However, changing the surface structure of nanocrystals and ensuring the exposure of active sites still face challenges. In this work, a three-dimensional self-supported catalyst with ultrathin Au nanoclusters encapsulated in Cu-doped ZIF-8 nanorod arrays on Ni foam (AuNC@ZIF-8(Cu) NRAs) is synthesized by a bottom-up strategy. This catalyst exhibits high catalytic activity with a 98% conversion of 4-nitrophenol to 4-aminophenol within 6 min. Meanwhile, it also has superior catalytic activity for other nitrobenzene compounds, such as 3-nitrophenol, 2-nitrophenol and p-nitroaniline. Furthermore, after 10 cycles, the catalytic performance and morphology of the catalyst have no obvious change. The excellent catalytic performance and stability of AuNC@ZIF-8(Cu) NRAs are attributed to the synergistic effect of ZIF-8(Cu) and AuNC. The doping of Cu in the ZIF-8 framework effectively alters the superficial electronic structure of encapsulated Au nanoclusters, which can dramatically promote the formation of gold hydride intermediates. The confinement effect of the porous ZIF-8 framework makes the AuNC active sites more stable and accessible to substrates. This method can be used to alter the activity of the catalyst by regulating the metal ion coordination of MOFs to influence the surface properties of encapsulated AuNC and opens the door to the rational design of new catalysts.

Highly efficient inverted solar cells based on perovskite grown nanostructures mediated by CuSCN.

In this work, three different CuSCN nanostructures (NSs), hexagonal prism-like (3D), pyramid-like (2D) and nanowire structures (NWs) are first applied to inverted heterojunction perovskite solar cells as p-type inorganic hole transport layers (HTLs) using a moderate electrodeposition method at room temperature. It is revealed that the crystal structure and the thickness of the CuSCN layer can dramatically regulate the morphology and the crystal orientation behavior of perovskite absorbing layers, which will further have a significant influence on the following device performance. Compared with the other two nanostructured CuSCN HTLs, devices based on 3D structured CuSCN HTLs exhibit better performance mainly attributed to the high crystalline quality of perovskite films controlled by the well-oriented hexagonal prism-like nanostructures of CuSCN. After optimization, a maximum power conversion efficiency (PCE) of 11.40% has been obtained with 3D CuSCN which has a thickness of 200 nm. It is the highest value among the current reports using nanostructured CuSCN as an inorganic HTL in inverted PSCs. The dominating effect of CuSCN nanostructures on the crystal quality of perovskites provides guidelines for future material optimization and device efficiency enhancement.

Novel inorganic perovskite quantum dots for photocatalysis.

Herein, we report the performance of CsPbX3 (X = Cl, Br, and I) perovskite quantum dots (QDs) for photocatalytic degradation of organic dyes. The photocatalytic performance of CsPbX3 QDs was characterized by UV-vis absorption spectra and ESI-MS, which evaluated their ability of degrading methyl orange (MO) solution under visible light irradiation. Interestingly, both CsPbCl3 and CsPbBr3 QDs show excellent photocatalytic activities, which can decompose the MO solution into a colorless solution within 100 min. This study demonstrates the potential of CsPbX3 QDs in the degradation of organic dyes and environmentally friendly applications. Moreover, the integration of CsPbX3 QDs and photocatalysis provides a new insight for the design of new photocatalysts.