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The transfer of the concept of chirality from molecules to synthesized nanomaterials has attracted attention amongst multidisciplinary teams. Here we demonstrate heterogeneous nucleation and anisotropic accumulation of Au nanoparticles on multilayer MoS2 planes to form chiroptically functional nanomaterials. Thiol amino acids with chiral conformations modulate asymmetric growth of gold nanoarchitectures on seeds of highly faceted Au/MoS2 heterostructures. Consequently, dendritic plasmonic nanocrystals with partial chiral morphologies are synthesized. The chirality of dendritic nanocrystals inherited from cysteine molecules refers to the structural characteristics and includes specific recognition of enantiomeric molecules. With integration of the intrinsic photothermal properties and inherited enantioselective characteristics, dendritic Au/MoS2 heterostructures exhibit chirality-dependent release of antimicrobial drugs from hydrogel substrates when activated by exogenous infrared irradiation. A three-in-one strategy involving synthesis of chiral dendritic heterostructures, enantioselective recognition, and controlled drug release system is presented, which improves nanomaterial synthetic technology and enhances our understanding of crucial chirality information. Chirality transfer from molecules to nanomaterials enables advanced optical functionalities. Here, the authors use exfoliated MoS2 nanosheets to seed the growth of chiral Au nanoparticles to form Au/MoS2 heterostructures for enantioselective drug release. [ABSTRACT FROM AUTHOR]

The synthesis of Co‐doped Mn3O4 nanocubes was achieved via galvanic replacement reactions for photo‐reduction of CO2. Co@Mn3O4 nanocubes could efficiently photo‐reduce CO2 to CO with a remarkable turnover number of 581.8 using [Ru(bpy)3]Cl2 ⋅ 6H2O as photosensitizer and triethanolamine as sacrificial agent in acetonitrile and water. The galvanic replaced Co species are homogeneously distributed at the outer surface of Mn3O4, providing catalytic active sites during CO2 reduction reactions, which facilitate the separation and migration of photogenerated charge carriers, further benefiting the outstanding photocatalytic performance of CO2 reduction. Density functional theory calculations revealed that the decreasing of conduction band maximum in Co@Mn3O4 was beneficial to the electron attachment from the excited sensitized molecule, which promoted photocatalytic reduction of CO2. [ABSTRACT FROM AUTHOR]

The chemical enhancement effects in surface-enhanced Raman scattering of p-aminothiophenol (PATP, it is also called p-mercaptoaniline or p-aminobenzenthiol) adsorbed on coinage metal surfaces with single thiol end or trapped into metal-molecule-metal junctions with both thiol and amino groups have been studied by density functional theory (DFT). We focus on the influence of photon-driven charge transfer (PDCT) and chemical bonding interaction (ground-state charge transfer) on the intensity enhancement and frequency shift in the surface Raman spectra of PATP. For comparison, the electronic structures and transitions of free PATP are studied first. The simulated pre-resonance UV Raman spectra illustrate that b2 modes can be selectively enhanced via vibronic coupling. The fundamentals of all the b2 modes in the frequency range of 1000 to 1650 cm-1 are assigned in detail. For PATP adsorbed on coinage metals, the time-dependent-DFT calculations indicate that the low-lying CT excited state arises from the π bonding orbital of molecule to the antibonding s orbital of metallic clusters. Our results further show that the PDCT resonance-like Raman scattering mechanism enhances the totally symmetric vibrational modes and the NH2 wagging vibration. Finally, the effect of chemical bonding interaction is also investigated. The amino group binding to metals gives a characteristic band of the NH2 wagging mode with the large blueshift frequency and an intense Raman signal. [ABSTRACT FROM AUTHOR]

The synthesis of aromatic azo compounds from anilines and nitrobenzene usually requires environmentally unfriendly transition metal catalysts. Here, we propose that azobenzene oligomers are formed in surface-enhanced Raman experiments assisted by surface plasmon resonance. The photocatalytic polymerization of p-dinitrobenzene (DNB) and p-phenylenediamine (PDA) to the corresponding azo-like oligomers on silver surfaces is studied by the surface-enhanced Raman spectroscopy and density functional theory. First, the normal Raman and surface Raman spectra of DNB and PDA are simulated and measured. The simulated normal Raman spectra are in good agreement with their solid-state Raman spectra. However, the simulated surface Raman spectra of DNB-Ag10 and PDA-Ag10 complexes are significantly different from the experimental surface-enhanced Raman spectra. We propose that DNBs has a reductive coupling and PDAs undergo an oxidative coupling reaction during SERS experiments. Secondly, the Raman spectra of the possible NN coupling oligomers of DNB and PDA are simulated. They are compared with the SERS spectra of DNB and PDA adsorbed on silver surfaces. Especially, the Raman spectra of p, p′-dinitroazobenzene and p, p′-diaminoazobenzene are in good agreement with the SERS spectra of DNB and PDA adsorbed on silver surface. Finally, two reaction mechanisms are proposed to explain the surface photocatalysis of DNB and PDA. In the solution, the nitro group of DNB can be reduced by the excited hot electrons. DNBs are then converted to p, p′-dinitroazobenzene through multiple proton and electron transfers. In the air and in the presence of O2, O2 is firstly activated through surface plasmon resonance. PDAs are then converted to p, p′-diaminoazobenzene by the generated active oxygen species. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of CO 2 is a promising route for converting intermittent renewable energy into storable fuels and useful chemical products. A theoretical investigation of the reaction mechanism and kinetics is beneficial for understanding the electrocatalytic activity and selectivity. In this report, a kinetic model based on Marcus theory is developed to compute the potential-dependent reaction barrier of the elementary concerted proton-electron transfer steps of electrochemical CO 2 reduction reactions, different from the previous hydrogen atom transfer model. It is found that the onset potentials and rate-determining steps for CO and CH 4 formation are determined by the first and third concerted proton-electron transfer steps C1 and C3. The influence of binding energy, electrode potential, and reorganization energy on the computed reaction barriers of the C1 and C3 reactions is discussed. In general, the calculated reaction barrier shows a quadratic relationship with the applied electrode potential. Specifically, the reaction barrier is merely determined by the reorganization energy at equilibrium potential. The present kinetic model is applied to compare the electrocatalytic activities in the electrochemical reduction of CO 2 on various copper crystal surfaces. Among the four studied copper single-crystal surfaces, Cu(211) exhibits the best electrocatalytic activity for CO formation and CH 4 formation due to its low onset potential and overpotential.

Surface plasmon resonances (SPRs) have been found to promote chemical reactions. In most oxidative chemical reactions oxygen molecules participate and understanding of the activation mechanism of oxygen molecules is highly important. For this purpose, we applied surface-enhanced Raman spectroscopy (SERS) to find out the mechanism of SPR-assisted activation of oxygen, by using p-aminothiophenol (PATP), which undergoes a SPR-assisted selective oxidation, as a probe molecule. In this way, SPR has the dual function of activating the chemical reaction and enhancing the Raman signal of surface species. Both experiments and DFT calculations reveal that oxygen molecules were activated by accepting an electron from a metal nanoparticle under the excitation of SPR to form a strongly adsorbed oxygen molecule anion. The anion was then transformed to Au or Ag oxides or hydroxides on the surface to oxidize the surface species, which was also supported by the heating effect of the SPR. This work points to a promising new era of SPR-assisted catalytic reactions., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)