Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

Semiconductor-based photocatalysis is considered to be an attractive way for solving the worldwide energy shortage and environmental pollution issues. Since the pioneering work in 2009 on graphitic carbon nitride (g-C3N4) for visible-light photocatalytic water splitting, g-C3N4 -based photocatalysis has become a very hot research topic. This review summarizes the recent progress regarding the design and preparation of g-C3N4 -based photocatalysts, including the fabrication and nanostructure design of pristine g-C3N4 , bandgap engineering through atomic-level doping and molecular-level modification, and the preparation of g-C3N4 -based semiconductor composites. Also, the photo-catalytic applications of g-C3N4 -based photocatalysts in the fields of water splitting, CO2 reduction, pollutant degradation, organic syntheses, and bacterial disinfection are reviewed, with emphasis on photocatalysis promoted by carbon materials, non-noble-metal cocatalysts, and Z-scheme heterojunctions. Finally, the concluding remarks are presented and some perspectives regarding the future development of g-C3N4 -based photocatalysts are highlighted.

Polymeric Photocatalysts Based on Graphitic Carbon Nitride

Although homogeneous gold catalysis was known previously, an exponential growth was only induced 12 years ago. The key findings which induce that rise of the field are discussed. This includes early reactions of allenes and furanynes and intermediates of these conversions as well as hydroarylation reactions. Other substrate types addressed are alkynyl epoxides and N-propargyl carboxamides. Important vinylgold intermediates, the transmetalation from gold to other transition metals, the development of new ligands for gold catalysis, and significant contributions from computational chemistry are other crucial points for the field highlighted here.

Gold-Catalyzed Organic Reactions

H 3 PMo 12 O 40 · x H 2 O and H 4 PVMo 11 O 40 · x H 2 O with Keggin structure were supported on SiO 2 –Al 2 O 3 carriers with Si/Al = 0.21 and 0.32 as well as on Al–MCM-41 (Si/Al = 10), characterized and monitored by operando-EPR in the dehydration of glycerol to acrolein at 553 K using feed streams of glycerol/N 2 /H 2 O/O 2  = 1/14.1/36.8/0.68 or 1/14.1/36.8/0. Upon deposition on the supports, the Keggin anions are degraded into fragments containing about 3–6 metal ions. Both the presence of vanadium as well as small amounts of O 2 in the feed keeps the Mo species in a highly oxidized state. This diminishes slightly the acrolein selectivity but also the condensation degree of the carbon deposits which might favour catalyst stability.

Impact of redox properties on dehydration of glycerol to acrolein over heteropolyacids assessed by operando-EPR spectroscopy

Vanadyl pyrophosphate catalysts were generated by dehydrating VOHPO4·(1/2)H2O at different temperatures and duration of the dehydration procedure. The as-synthesised materials were characterised by X-ray diffractometry, FTIR spectroscopy and temperature-programmed reduction. The prolongation of the formation period at higher temperatures led to improved crystallinity and lower BET surface areas of the vanadyl pyrophosphate specimens and, additionally, a significantly impeded reducibility of the vanadyl sites was observed. The catalytic performance of the samples was tested in the partial oxidation of toluene to benzaldehyde. The obtained results revealed an increasing benzaldehyde selectivity with improved catalyst crystallinity. In situ FTIR and ESR spectroscopy were used to throw more light on the interaction of the toluene–air feed with the surface of the catalyst.

Catalytic performance of vanadyl pyrophosphate in the partial oxidation of toluene to benzaldehyde

Differently prepared vanadyl pyrophosphate and potassium-doped vanadia catalysts have been studied during the selective oxidation of toluene and p -methoxy toluene to the corresponding benzaldehydes using a portfolio of various in situ-methods (EPR, UV–VIS–DRS, XRD and XPS). The poor catalytic performance of (VO) 2 P 2 O 7 is mainly due to strong product adsorption which is favoured by surface OH-groups formed under reaction conditions. This process can be partially suppressed by adding competitive adsorbates to the feed. In K-V 2 O 5 catalysts, a potassium vanadate phase is formed on the surface in which about 25% of the vanadium ions are tetravalent. This leads to lower acidity and oxidation potential of the surface and, thus, to improved benzaldehyde selectivities.

A new approach to study the gas-phase oxidation of toluene: probing active sites in vanadia-based catalysts under working conditions

Bimetallic PdAu-KOac/SiO2 catalysts for vinyl acetate monomer (VAM) synthesis : Insights into deactivation under industrial conditions

https://pure.mpg.de/pubman/item/item_736423_2/component/file_736422/429329solid%20state%20sciences%202009.pdf

Angelika Brückner

Papers

Impact of redox properties on dehydration of glycerol to acrolein over heteropolyacids assessed by operando-EPR spectroscopy

Catalytic performance of vanadyl pyrophosphate in the partial oxidation of toluene to benzaldehyde

A new approach to study the gas-phase oxidation of toluene: probing active sites in vanadia-based catalysts under working conditions

Bimetallic PdAu-KOac/SiO2 catalysts for vinyl acetate monomer (VAM) synthesis : Insights into deactivation under industrial conditions

The crystal structure of δ-VOPO4 and its relationship to ω-VOPO4