Facile and Controlled Fabrication of Functional Gold Nanoparticle‐coated Polystyrene Composite Particle

Gold nanoparticles‐coated polystyrene (AuNPs‐coated PS) composite particles with raspberry‐like morphology are successfully prepared with the aid of a unique thermodynamically driving effect. It is of considerable interest that the AuNPs generate and self‐assemble with raw, ordinary PS microspheres that preexist in the oxidation–reduction systems. The synthesized AuNPs‐coated PS composite particles have been extensively characterized using scanning electron microscope, transmission electron microscope, and UV–Vis‐NIR spectroscopy. The results indicate that the morphology of the resultant composite particles is governed by simply changing the amount and type of reductants and the concentration of PS microspheres. The AuNPs‐coated PS composite particles also exhibit the good surface‐enhanced Raman scattering and catalytic performances.

     

A Facile One‐Pot Synthesis of Layered Protonated Titanate Nanosheets Loaded with Silver Nanoparticles with Enhanced Visible‐Light Photocatalytic Performance

Layered protonated titanate nanosheets (LPTNs) loaded with silver nanoparticles are prepared by a simple one‐pot hydrothermal route in silver‐ammonia solution. The as‐synthesized Ag‐loaded LPTNs possess large specific surface area. The Ag nanoparticles are highly dispersed on the surface of the LPTNs. They have negligible effects on the crystal structure, crystallinity, and surface area of the LPTNs but result in considerable enhancement of visible‐light absorption and in a red‐shift of the band gap for the LPTNs. The Ag‐loaded LPTNs show enhanced photocatalytic activity for both liquid‐ and gas‐phase reactions under visible‐light irradiation. Moreover, the photocatalytic activity first increases gradually with increasing Ag loading content, and then decreases after maximizing at an optimal Ag content. At the Ag loading content of 2.87 mol % and 1.57 mol %, the Ag‐loaded LPTNs exhibit the highest visible‐light photocatalytic activity for degradation of rhodamine B in water and mineralization of benzene in air, respectively. An alternative possible mechanism for the enhancement of the visible‐light photocatalytic activity is also proposed.     

Polysiloxane‐Backbone Block Copolymers in a One‐Pot Synthesis: A Silicone Platform for Facile Functionalization

Block copolymers consisting exclusively of a silicon–oxygen backbone are synthesized by sequential anionic ring‐opening polymerization of different cyclic siloxane monomers. After formation of a poly(dimethylsiloxane) (PDMS) block by butyllithium‐initiated polymerization of D3, a functional second block is generated by subsequent addition of tetramethyl tetravinyl cyclotetrasiloxane (D4^V), resulting in diblock copolymers comprised a simple PDMS block and a functional poly(methylvinylsiloxane) (PMVS) block. Polymers of varying block length ratios were obtained and characterized. The vinyl groups of the second block can be easily modified with a variety of side chains using hydrosilylation chemistry to attach compounds with Si—H bond. Conversion of the hydrosilylation used for polymer modification was investigated.     

A Cascade‐Reaction Nanoreactor Composed of a Bifunctional Molecularly Imprinted Polymer that Contains Pt Nanoparticles

This study was aimed at addressing the present challenge of cascade reactions, namely, how to furnish the catalysts with desired and hierarchical catalytic ability. This issue was addressed by constructing a cascade‐reaction nanoreactor made of a bifunctional molecularly imprinted polymer containing acidic catalytic sites and Pt nanoparticles. The acidic catalytic sites within the imprinted polymer allowed one specified reaction, whereas the encapsulated Pt nanoparticles were responsible for another coupled reaction. To that end, the unique imprinted polymer was fabricated by using two well‐coupled templates, that is, 4‐nitrophenyl acetate and 4‐nitrophenol. The catalytic hydrolysis of the former compound at the acidic catalytic sites led to the formation of the latter compound, which was further reduced by the encapsulated Pt nanoparticles to 4‐aminophenol. Therefore, this nanoreactor demonstrated a catalytic‐cascade ability. This protocol opens up the opportunity to develop functional catalysts for complicated chemical processes.     

Tailored Synthesis of Various Nanomaterials by Using a Graphene‐Oxide‐Based Gel as a Nanoreactor and Nanohybrid‐Catalyzed CC Bond Formation

New graphene oxide (GO)‐based hydrogels that contain vitamin B₂/B₁₂ and vitamin C (ascorbic acid) have been synthesized in water (at neutral pH value). These gel‐based soft materials have been used to synthesize various metal nanoparticles, including Au, Ag, and Pd nanoparticles, as well as nanoparticle‐containing reduced graphene oxide (RGO)‐based nanohybrid systems. This result indicates that GO‐based gels can be used as versatile reactors for the synthesis of different nanomaterials and hybrid systems on the nanoscale. Moreover, the RGO‐based nanohybrid hydrogel with Pd nanoparticles was used as an efficient catalyst for C? C bond‐formation reactions with good yields and showed high recyclability in Suzuki–Miyaura coupling reactions.     

Iron(III)‐Quantity‐Dependent Aggregation–Dispersion Conversion of Functionalized Gold Nanoparticles

Developing gold nanoparticles (AuNPs) with well‐designed functionality is highly desirable for boosting the performance and versatility of inorganic–organic hybrid materials. In an attempt to achieve ion recognition with specific signal expressions, we present here 4‐piperazinyl‐1,8‐naphthalimide‐functionalized AuNPs for the realization of quantitative recognition of Fe^III ions with dual (colorimetric and fluorescent) output. The research takes advantage of 1) quantity‐controlled chelation‐mode transformation of the piperazinyl moiety on the AuNPs towards Fe^III, thereby resulting in an aggregation–dispersion conversion of the AuNPs in solution, and 2) photoinduced electron transfer of a naphthaimide fluorophore on the AuNPs, thus leading to reversible absorption and emission changes. The functional AuNPs are also responsive to pH variations. This strategy for realizing the aggregation–dispersion conversion of AuNPs with returnable signal output might exhibit application potential for advanced nanoscale chemosensors.     

Electrocatalytic Oxidation of Tryptophan at Gold Nanoparticle‐Modified Carbon Ionic Liquid Electrode

The electrochemical behavior of tryptophan was studied at the carbon ionic liquid electrode (CILE) modified with gold nanoparticle (GNP). This electrode has a stable and excellent response toward tryptophan. Under optimum experimental conditions, the calibration curve was linear in the tryptophan concentration range of 5 to 900 µM with an excellent correlation coefficient (0.995). The experimental limit of detection was 4 µM. Contrary to many other electrodes, the oxidation of tryptophan on GNP/CILE does not result in electrode fouling. GNP/CILE has been effectively applied to the determination of tryptophan in composite amino acid injection.     

Gold Nanoparticles Supported on a Layered Double Hydroxide as Efficient Catalysts for the One‐Pot Synthesis of Flavones

Flavones are a class of natural products with diverse biological activities and have frequently been synthesized by step‐by‐step procedures using stoichiometric amounts of reagents. Herein, a catalytic one‐pot procedure for the synthesis of flavone and its derivatives is developed. In the presence of gold nanoparticles supported on a Mg‐Al layered double hydroxide (Au/LDH), various kinds of flavones can be synthesized starting from 2′‐hydroxyacetophenones and benzaldehydes (or benzyl alcohols). The present one‐pot procedure consists of a sequence of several reactions, and Au/LDH can catalyze all these different types of reactions. The catalysis is shown to be truly heterogeneous, and Au/LDH can be readily recovered and reused.     

Synthesis of Nipagin Esters Using Acidic Functional Ionic Liquids as Catalysts

Several Brønsted acidic functional ionic liquids (FILs) with an alkane sulfonic acid group were synthesized. These FILs as dual solvent-catalysts for Nipagin esterification reactions were investigated. The results indicated that [HSO₃-pMIM]HSO₄ has the best catalytic activity and recyclability among the various kinds of FILs investigated, and its structure was characterized by infrared and NMR. The [HSO₃-pMIM]HSO₄ could be easily separated from the reaction mixture and reused without noticeably decreasing the catalytic activity.

Microwave Irradiation for the Facile Synthesis of Transition‐Metal Nanoparticles (NPs) in Ionic Liquids (ILs) from Metal–Carbonyl Precursors and Ru‐, Rh‐, and Ir‐NP/IL Dispersions as Biphasic Liquid–Liquid Hydrogenation Nanocatalysts for Cyclohexene

Stable chromium, molybdenum, tungsten, manganese, rhenium, ruthenium, osmium, cobalt, rhodium, and iridium metal nanoparticles (M‐NPs) have been reproducibly obtained by facile, rapid (3 min), and energy‐saving 10 W microwave irradiation (MWI) under an argon atmosphere from their metal–carbonyl precursors [M_x(CO)_y] in the ionic liquid (IL) 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIm][BF₄]). This MWI synthesis is compared to UV‐photolytic (1000 W, 15 min) or conventional thermal decomposition (180–250 °C, 6–12 h) of [M_x(CO)_y] in ILs. The MWI‐obtained nanoparticles have a very small (<5 nm) and uniform size and are prepared without any additional stabilizers or capping molecules as long‐term stable M‐NP/IL dispersions (characterization by transmission electron microscopy (TEM), transmission electron diffraction (TED), and dynamic light scattering (DLS)). The ruthenium, rhodium, or iridium nanoparticle/IL dispersions are highly active and easily recyclable catalysts for the biphasic liquid–liquid hydrogenation of cyclohexene to cyclohexane with activities of up to 522 (mol product) (mol Ru)^?1 h^?1 and 884 (mol product) (mol Rh)^?1 h^?1 and give almost quantitative conversion within 2 h at 10 bar H₂ and 90 °C. Catalyst poisoning experiments with CS₂ (0.05 equiv per Ru) suggest a heterogeneous surface catalysis of Ru‐NPs.     

Facile One‐Pot Fabrication of Hollow Porous Silica Nanoparticles

A method for the fabrication of hollow silica nanospheres, a facile one‐pot hydrothermal route, is described. Heating of an aqueous solution of water glass and D ‐glucose to 180 °C for 24 h affords—as indicated by transmission electron microscopy—a nanospherical composite consisting of a silica shell sheathing a carbonaceous core. Subsequent removal of the carbonaceous interior through oxidation in air produces hollow silica structures. Variation of the concentration of the two jointly dissolved chemicals enables a variation of the thickness of the silica shell. The hollow silica particles were characterized by means of SEM, TEM, XRD, IR spectroscopy, thermogravimetrical analysis (TGA), and sorption measurements.     

One‐Pot Sequence‐Controlled Synthesis of Oligosiloxanes

Silicones (organopolysiloxanes) have found applications in a wide range of research areas, and their unique and valuable properties have rendered these materials virtually irreplaceable. Despite the fact that silicones have been employed industrially for more than 70 years, synthetic routes to generate silicones remain limited, and the sequence‐controlled synthesis of oligo‐ and polysiloxanes still represents a major challenge in silicone chemistry. Described here is a highly selective sequence‐controlled synthesis of linear, branched, and cyclic oligosiloxanes by simple iteration of two reactions, specifically, a B(C₆F₅)₃‐catalyzed dehydrocarbonative cross‐coupling of alkoxysilanes with hydrosilanes and a B(C₆F₅)₃‐catalyzed hydrosilylation of carbonyl compounds, in a single flask. The sequence of the resulting oligosiloxanes can be controlled precisely by the order of addition of the hydrosilane monomers.     

Nanotexaphyrin: One‐Pot Synthesis of a Manganese Texaphyrin‐Phospholipid Nanoparticle for Magnetic Resonance Imaging

The discovery and synthesis of novel multifunctional organic building blocks for nanoparticles is challenging. Texaphyrin macrocycles are capable and multifunctional chelators. However, they remain elusive as building blocks for nanoparticles because of the difficulty associated with synthesis of texaphyrin constructs capable of self‐assembly. A novel manganese (Mn)‐texaphyrin‐phospholipid building block is described, along with its one‐pot synthesis and self‐assembly into a Mn‐nanotexaphyrin. This nanoparticle possesses strong resilience to manganese dissociation, structural stability, in vivo bio‐safety, and structure‐dependent T₁ and T₂ relaxivities. Magnetic resonance imaging (MRI) contrast enhanced visualization of lymphatic drainage is demonstrated with respect to proximal lymph nodes on the head and neck VX‐2 tumors of a rabbit. Synthesis of 17 additional metallo‐texaphyrin building blocks suggests that this novel one‐pot synthetic procedure for nanotexaphyrins may lead to a wide range of applications in the field of nanomedicines.     

Facile One‐Pot Synthesis of Functional Giant Polymeric Vesicles Controlled by Oscillatory Chemistry

We introduce a novel application of an oscillatory chemical reaction to the synthesis of block copolymers. The Belousov–Zhabotinsky (B‐Z) reaction is coupled with the polymerization of an amphiphilic block copolymer. Radicals generated in the B‐Z reaction initiate the polymerization between a polyethylene glycol (PEG) macroreversible addition‐fragmentation chain‐transfer agent and butyl acrylate monomers. The attachment of a hydrophobic block on PEG leads to self‐assembly and formation of spherical micelles. The nanoscale micelles transform into submicrometer vesicles and grow to giant vesicles as a consequence of the oscillatory behavior of the B‐Z reaction. The one‐pot synthesis of an amphiphilic di‐block copolymer and retention of oscillatory behavior for the B‐Z reaction with the formation of giant vesicles bring a new insight into possible pathways for the synthesis of active functional microreactors in the range from hundreds of nanometers to tens of micrometers.     

Visible‐Light‐Induced Electron Transport from Small to Large Nanoparticles in Bimodal Gold Nanoparticle‐Loaded Titanium(IV) Oxide

A key to realizing the sustainable society is to develop highly active photocatalysts for selective organic synthesis effectively using sunlight as the energy source. Recently, metal‐oxide‐supported gold nanoparticles (NPs) have emerged as a new type of visible‐light photocatalysts driven by the excitation of localized surface plasmon resonance of Au NPs. Here we show that visible‐light irradiation (λ>430 nm) of TiO₂‐supported Au NPs with a bimodal size distribution (BM‐Au/TiO₂) gives rise to the long‐range (>40 nm) electron transport from about 14 small (ca. 2 nm) Au NPs to one large (ca. 9 nm) Au NP through the conduction band of TiO₂. As a result of the enhancement of charge separation, BM‐Au/TiO₂ exhibits a high level of visible‐light activity for the one‐step synthesis of azobenzenes from nitrobenzenes at 25 °C with a yield greater than 95 % and a selectivity greater than 99 %, whereas unimodal Au/TiO₂ (UM‐Au/TiO₂) is photocatalytically inactive.