Ligand effect on the catalytic activity of gold clusters in the electrochemical hydrogen evolution reaction.

Novel boron–dibenzopyrromethene dyes with thienyl-cyanoacrylic acid units were synthesized and characterized for application in dye-sensitized solar cells (DSSCs).

Composites of organic molecules and inorganic quantum dots (QDs) have emerged as attractive photon upconversion systems that use triplet–triplet annihilation upconversion (TTA-UC). However, the upconversion efficiency of such systems is still far from reaching their theoretical potential. The number of acceptor molecules directly coordinated on a QD (n) should determine triplet–triplet energy transfer (TTET) efficiency (ΦTTET), which consequently affects the efficiency of TTA-UC, but the research focusing on the n value has been limited. In the present report, the effect of n on TTET from CdSe or CdTe QDs to perylene-3-carboxylic acid (Pe; i.e., acceptor) were systematically investigated. The TTET and TTA-UC efficiencies increase with increasing n. The regulation of n on a QD could provide a straightforward means to realize high-performance TTA-UC. For the molecule/QDs systems, small QDs with a wide band gap are favorable for intrinsic TTET (i.e., TTET in a one-to-one QD-Pe composite system), because intrinsic TTET efficiency is detemined by the triplet energy of QDs. On the other hand, the small QDs limit the n due to the small surface area. Therefore, the proper choices of QDs and acceptors providing both sufficient free energy change for TTET and large n are important to achieve efficient TTA-UC.

The orientation of a molecule on a metal surface can impact the performance of electronic devices fabricated from organic materials. This orientation effect of physiosorbed or weakly chemisorbed molecules has been widely debated, and its origin remains unknown because methods to investigate the weak interaction at the molecule/inert-metal interface have been limited. Here, it is shown via spectroscopy and density functional calculations that molecule/metal orbital hybridization, which is determined by the molecular orientation, is an identity of the orientation effect dictating the carrier dynamics at the interface. Nanoscale model interfaces, where molecules were weakly chemisorbed on a metal, made it possible to visualize the orientation-dependent shift of the electronic state. The transient absorption spectroscopy and scanning tunneling spectroscopy of porphyrin derivative coordinated on gold nanoparticle demonstrated that the orbital hybridization dictates the interfacial carrier dynamics. This new understanding of the molecule/metal interfaces will enable functional-molecule designs based on the cross-materials orbital hybridization for various devices.