Blue-LED activated photocatalytic hydrogenation of nitroarenes with Cu2O/CuO heterojunctions.

This study describes how the optimization of Cu2O/CuO heterostructures can enhance their (photo)catalytic performance. More specifically, the evaluation of catalysts with different Cu2O/CuO molar ratios was used to optimize their performance for the hydrogenation of 4-nitrophenol under both blue-LED light and dark conditions. For the first time, we analyzed the effect of blue LED irradiation on this reaction and found that when blue LEDs are used as the light source, a Cu2O/CuO ratio of 0.15 results in rate constants 7 to 3 times higher than those of catalysts with either lower (0.01) or higher (0.42) ratios. Furthermore, this photocatalyst shows good stability, >70% after 5 cycles, and excellent chemoselectivity in the selective reduction of the nitro group in the presence of other functionalities, i.e. -COOH, -CONH2 and -OH.

Non-covalent Functionalization of Graphene to Tune Its Band Gap and Stabilize Metal Nanoparticles on Its Surface.

Controlling graphene conductivity is crucial for its potential applications. With this focus, this paper shows the effect of the non-covalent bonding of a pyrimidine derivative (HIS) on the electronic properties of graphene (G). Several G-HIS hybrids are prepared through mild treatments keeping unaltered the structures of both G and HIS. The attachment of HIS to G occurs by π-π stacking of the HIS-aromatic residue with the G surface. This partially blocks the p z electrons of G, giving rise to the splitting of both the valence and conduction bands. Moreover, the width of the splitting is directly related to the HIS content. This fact allows the fine-tuning of the band gap of G-HIS hybrids. Furthermore, HIS keeps its metal-complexing ability in the G-HIS hybrids. Taking advantage of this, a G-HIS-Cu(0) composite was prepared by H2 plasma reduction of a precursor of the G-HIS-Cu(II) type. G-HIS-Cu(0) contains Cu(0) clusters stabilized on the G surface due to interactions with the COO- functions of HIS. In an analogous hybrid, G-HIS-Au(0), the Au(0) NPs are also stabilized by COO- functions. This material, consisting of the coupling of Au(0) NPs and G-HIS, photocatalyzed water reduction under visible light radiation producing 12.5 µmol·g-1·h-1of hydrogen.