SuFExable polymers with helical structures derived from thionyl tetrafluoride.

Sulfur(VI) fluoride exchange (SuFEx) is a category of click chemistry that enables covalent linking of modular units through sulfur(VI) connective hubs. The efficiency of SuFEx and the stability of the resulting bonds have led to polymer chemistry applications. Now, we report the SuFEx click chemistry synthesis of several structurally diverse SOF4-derived copolymers based on the polymerization of bis(iminosulfur oxydifluorides) and bis(aryl silyl ethers). This polymer class presents two key characteristics. First, the [-N=S(=O)F-O-] polymer backbone linkages are themselves SuFExable and undergo precise SuFEx-based post-modification with phenols or amines to yield branched functional polymers. Second, studies of individual polymer chains of several of these new materials indicate helical polymer structures. The robust nature of SuFEx click chemistry offers the potential for post-polymerization modification, enabling the synthesis of materials with control over composition and conformation.

Fast room-temperature functionalization of silicon nanoparticles using alkyl silanols.

Silicon nanoparticles (Si NPs) are a good alternative to conventional heavy metal-containing quantum dots in many applications, due to their low toxicity, low cost, and the high natural abundance of the starting material. Recently, much synthetic progress has been made, and crystalline Si NPs can now be prepared in a matter of hours. However, the passivation of these particles is still a time-consuming and difficult process, usually requiring high temperatures and/or harsh reaction conditions. In this paper, we report an easy method for the room-temperature functionalization of hydrogen-terminated Si NPs. Using silanol compounds, a range of functionalized Si NPs could be produced in only 1 h reaction time at room temperature. The coated NPs were fully characterized to determine the efficiency of binding and the effects of coating on the optical properties of the NPs. It was found that Si NPs were effectively functionalized, and that coated NPs could be extracted from the reaction mixture in a straightforward manner. The silanol coating increases the quantum yield of fluorescence, decreases the spectral width and causes a small (∼50 nm) blue-shift in both the excitation and emission spectra of the Si NPs, compared to unfunctionalized particles.

Methanol Synthesis Using CO2 and H2 on Nano Silver-Ceria Zirconia Catalysts: Influence of Preparation Method.

Silver catalysts supported on ceria-zirconia (CZ) mechanically mixed oxide were synthesized by wet impregnation and chelating methods. Nominal loadings of 5 wt.% of Ag was deposited on the CZ support. These catalysts were tested for the CO2 hydrogenation reaction to methanol with feed gas composition of CO2-H2 = 3:1 at 250 °C, 20 bar total pressure and GHSV of 1800 h-1. The calcined and reduced catalysts were characterized using XRD, BET, TPR, SEM-EDS, XPS and FTIR-DRIFTs techniques. Finely deposited silver crystallites sized in the range of 20-50 nm were observed through SEM and HR-TEM analysis. TPR and XRD studies demonstrated the presence of Ag2O and metallic silver (Ag0) on CZ support. About 10% of CO formation was observed on chelating catalyst (5Ag/CZ CHE). However, only, 5% CO was observed on impregnated (5Ag/CZ IMP) catalyst. The greater CO formation was associated with ease reduction of Ag2O to metallic silver in 5Ag/CZ CHE catalyst. Further, 70% of methanol selectivity was observed on 5Ag/CZ IMP due to the presence of Ag2O on CZ. FTIR-DRIFTs results revealed the methanol formation via formate intermediates and CO formation via RWGS reaction on the studied catalysts.

One-Pot Gram-Scale Synthesis of Hydrogen-Terminated Silicon Nanoparticles.

Silicon nanoparticles (Si NPs) are highly attractive materials for typical quantum dots functions, such as in light-emitting and bioimaging applications, owing to silicon's intrinsic merits of minimal toxicity, low cost, high abundance, and easy and highly stable functionalization. Especially nonoxidized Si NPs with a covalently bound coating serve well in these respects, given the minimization of surface defects upon hydrosilylation of H-terminated Si NPs. However, to date, methods to obtain such H-terminated Si NPs are still not easy. Herein, we report a new synthetic method to produce size-tunable robust, highly crystalline H-terminated Si NPs (4-9 nm) using microwave irradiation within 5 min at temperatures between 25 and 200 °C and their further covalent functionalization. The key step to obtain highly fluorescent (quantum yield of 7-16%) green-red Si NPs in one simple step is the reduction of triethoxysilane and (+)-sodium l-ascorbate, yielding routinely ∼1 g of H-Si NPs via a highly scalable route in 5-15 min. Subsequent functionalization via hydrosilylation yielded Si NPs with an emission quantum yield of 12-14%. This approach can be used to easily produce high-quality H-Si NPs in gram-scale quantities, which brings the application of functionalized Si NPs significantly closer.