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A nanophotonic modulator is proposed based on Silicon-ITO (Indium Tin Oxide) heterojunction and slot waveguide with 2D-graphene sheets. It combines the advantage of 2D materials, heterojunctions, and slot waveguides. A 1550-nm light is guided and confined in a nano slot of p-silicon rib, which is filled with semimetal n-ITO. The graphene sheet is used for modulation due to its unique properties, such as absorption turned off due to state filling or Pauli-blocking, to minimize the insertion loss to 0.07 dB/µm with the tuning of Fermi levels in an extensive range of wavelengths at different voltages. The device has shown dual characteristics at different sets of voltages. It works as an absorptive modulator (amplitude modulator) between 0 and 2 V and as an electro-optic modulator from 2 to 5 V. An outstanding π shift at only 32 µm for a voltage of 3 V and a very high extinction ratio of 25 dB for 20 µm of the waveguide is observed. The electrical characteristic of the device shows low power consumption active device length product of VπL = 64 Vµm. A study of TE polarization of light using graphene sheets is also presented in this paper. The device has applications for phase and amplitude modulations in silicon on-chip communication and interconnects.

A series of N‐substituted iminopyridine ligand‐based arene–RuIIcomplexes with general formula [(η6‐arene)Ru(C5H4N‐2‐CH=NR)Cl]+was synthesized and characterized by NMR spectroscopy, mass spectrometry, and single‐crystal X‐ray diffraction studies. The synthesized arene–RuIIcomplexes showed high activity in the regioselective Markovnikov hydration of a range of aromatic and aliphatic terminal alkynes and produced moderate to good yields of the corresponding methyl ketones. Moreover, the RuIIcatalysts studied showed good recyclability. The mechanism of the RuII‐catalyzed hydration reaction was investigated in detail by performing mass experiments and control experiments, followed by the identification of crucial RuII–alkyne and RuII–vinyl organometallic species. Add water: Half‐sandwich arene–RuIIcomplexes of bidentate N‐substituted iminopyridine ligands were synthesized as catalysts for the regioselective Markovnikov hydration of terminal alkynes to methyl ketones. The complexes catalyzed the reaction of a variety of aromatic, aliphatic and bulkier substrates, and were readily recycled. Mechanistic studies revealed important organometallic RuII–η2‐alkyne and RuII–vinyl intermediates, which favorably drive the reaction.

A series of water-soluble troponate/aminotroponate ruthenium(II)–arene complexes were synthesized, where O,O and N,O chelating troponate/aminotroponate ligands stabilized the piano-stoolmononuclear ruthenium–arene complexes. Structural identities for two of the representating complexes were also established by single-crystal X-ray diffraction studies. These newly synthesized troponate/aminotroponate ruthenium–arene complexes enable efficient C–H bond arylation of arylpyridine in water. The unique structure–activity relationship in these complexes is the key to achieve efficient direct C–H bond arylation of arylpyridine. Moreover, the steric bulkiness of the carboxylate additives systematically directs the selectivity toward mono- versus diarylation of arylpyridines. Detailed mechanistic studies were performed using mass-spectral studies including identification of several key cyclometalated intermediates. These studies provided strong support for an initial cycloruthenation driven by carbonate-assisted deprotonation of 2-phenylpyridine, where the relative strength of η6-arene and the troponate/aminotroponate ligand drives the formation of cyclometalated 2-phenylpyridine Ru–arene species, [(η6-arene)Ru(κ2-C,N-phenylpyridine) (OH2)]+by elimination of troponate/aminotroponate ligands and retaining η6-arene, while cyclometalated 2-phenylpyridine Ru–troponate/aminotroponate species [(κ 2-troponate/aminotroponate)Ru(κ2-C,N-phenylpyridine)(OH2)2] was generated by decoordination of η6-arene ring during initial C–H bond activation of 2-phenylpyridine. Along with the experimental mass-spectral evidence, density functional theory calculation also supports the formation of such species for these complexes. Subsequently, these cycloruthenated products activate aryl chloride by facile oxidative addition to generate C–H arylated products.

Molecular catalysts based on water-soluble arene-Ru(II) complexes ([Ru]-1–[Ru]-5) containing aniline (L1), 2-methylaniline (L2), 2,6-dimethylaniline (L3), 4-methylaniline (L4), and 4-chloroaniline (L5) were designed for the homocoupling of arylboronic acids in water. These complexes were fully characterized by 1H, 13C NMR, mass spectrometry, and elemental analyses. Structural geometry for two of the representative arene-Ru(II) complexes [Ru]-3and [Ru]-4was established by single-crystal X-ray diffraction studies. Our studies showed that the selectivity toward biaryls products is influenced by the position and the electronic behavior of various substituents of aniline ligand coordinated to ruthenium. Extensive investigations using 1H NMR, 19F NMR, and mass spectral studies provided insights into the mechanistic pathway of homocoupling of arylboronic acids, where the identification of important organometallic intermediates, such as σ-aryl/di(σ-aryl) coordinated arene-Ru(II) species, suggested that the reaction proceeds through the formation of crucial di(σ-aryl)-Ru intermediates by the interaction of arylboronic acid with Ru-catalyst to yield biaryl products.

Catalysts based on bimetallic nanoparticles have received tremendous scientific and industrial attention and are established as an important class of active catalysts. These catalysts displayed improved catalytic activities compared to their monometallic counterparts for several reactions, which is attributed to their highly modified surface structures (electronic and geometrical) due to the synergic cooperation between the two metals of the bimetallic nanoparticle catalyst. Moreover, such synergic interactions are more prominent in alloy nanoparticle catalysts, where the probability of metal-to-metal interactions is higher in comparison with other systems (such as core–shell nanoparticles). This minireviewhighlights the recent progress made in the last decade towards the development of activated bimetallic alloy nanoparticle catalysts for C–C coupling reactions, including asymmetric C–C bond coupling reactions. Herein, the influence of the modified electronic structures of the newly formed bimetallic alloy nanoparticle catalysts on their activated catalytic performance is also discussed extensively.

Bimetallic Ni–Pd alloy nanoparticles with high Ni to Pd atomic ratios (99 : 1 or 95 : 5) were prepared, and the catalytic performances of these nanoparticle catalysts were explored for C–C coupling reactions (Suzuki–Miyaura, Heck and Sonogashira reactions) under moderate reaction conditions. In contrast to their monometallic counterparts, significantly enhanced catalytic activity was achieved with the studied Ni–Pd nanoparticle catalysts for the C–C coupling reactions, and products were obtained in moderate to high yields. The turnover number (TON) increases with the increase in the Ni to Pd atomic ratio for Ni–Pd nanoparticle catalysts and can reach 3.6 × 103for Ni0.99Pd0.01nanoparticle catalysed Suzuki–Miyaura reaction of aryl bromides with arylboronic acid at 50 °C. Advantageously, such Ni–Pd nanoparticle catalysts with high Ni to Pd atomic ratios not only show significantly enhanced catalytic activity but are also stable (ICP-AES analysis showed only marginal or no Pd leaching) and retain their catalytic activities for several catalytic runs (>90% conversion even at the 7th catalytic run). Experimental and relevant theoretical calculations (net charge localization using first principles calculations) suggested a substantial Ni to Pd charge transfer which resulted in a highly negatively charged Pd centre, a favourable site for facile oxidative addition of aryl halides, and hence enhanced catalytic activity for Ni–Pd nanoparticle catalysts.