Effects of hectorite content on the temperature-sensitivity of PNIPAM microgels

A new method, adopting inorganic clay (synthetic hectorite) as a physical cross-linker, was used to prepare poly(N-isopropylacrylamide) (PNIPAM) microgels via surfactant-free emulsion polymerization. The effect of hectorite content on the temperature-sensitivity of PNIPAM microgels was investigated by means of DLS, UV/Vis and DSC. It was found that, in the absence of surfactant, with increasing hectorite content, the particle size tends to decrease to 300 nm at room temperature, while increases as weight ratio (WR) of hectorite and N-isopropylacrylamide (NIPAM) exceeds 21%. Furthermore, with increasing WR from 7% to 21%, the volume phase transition temperature of PNIPAM microgels has little shift, while decreases slightly when WR increases up to 28%.     

Parallel demodulation system and signal-processing method for extrinsic Fabry-Perot interferometer and fiber Bragg grating sensors

A parallel demodulation system for extrinsic Fabry-Perot interferometer (EFPI) and fiber Bragg grating (FBG) sensors is presented that is based on a Michelson interferometer and combines the methods of low-coherence interference and Fourier transform spectrum. Signals from EFPI and FBG sensors are obtained simultaneously by scanning one arm of a Michelson interferometer, and an algorithm model is established to process the signals and retrieve both the wavelength of the FBG and the cavity length of the EFPI at the same time, which are then used to determine the strain and temperature.     

Direct Formation of C−C Triple‐Bonded Structural Motifs by On‐Surface Dehalogenative Homocouplings of Tribromomethyl‐Substituted Arenes

On‐surface synthesis shows significant potential in constructing novel nanostructures/nanomaterials, which has been intensely studied in recent years. The formation of acetylenic scaffolds provides an important route to the fabrication of emerging carbon nanostructures, including carbyne, graphyne, and graphdiyne, which feature chemically vulnerable sp‐hybridized carbon atoms. Herein, we designed and synthesized a tribromomethyl‐substituted compound. By using a combination of high‐resolution scanning tunneling microscopy, non‐contact atomic force microscopy, and density functional theory calculations, we demonstrated that it is feasible to convert these compounds directly into C?C triple‐bonded structural motifs by on‐surface dehalogenative homocoupling reactions. Concurrently, sp³‐hybridized carbon atoms are converted into sp‐hybridized ones, that is, an alkyl group is transformed into an alkynyl moiety. Moreover, we achieved the formation of dimer structures, one‐dimensional molecular wires, and two‐dimensional molecular networks on Au(111) surfaces, which should inspire further studies towards two‐dimensional graphyne structures.     

Electrochemical quartz crystal microbalance characterization of I(-) and its amperometric detection by microelectrode

The electrochemical redox mechanism of I(-) ion under different concentrations on gold electrodes was studied in detail using the EQCM technique (a combination of the QCM technique and cyclic voltammetry). The redox behavior of the I(-) ion on a gold microelectrode when no supporting electrolyte was added was compared with a conventional gold microelectrode. Due to the small current and the very low solution iR drop of the microelectrode, the actual oxidation potential of I(-) on the microelectrode was much more negative than that of the conventional electrode and its anodic peak was better defined. Therefore the gold microelectode was employed for the determination of I(-). A linear range of 1.0x10(-5)-0.1 mol l(-1) with a detection limit of 1.0x10(-6) mol l(-1) was obtained on the microelectrode in pure KI aqueous solution. Two samples were measured using this method and the results were in good agreement with those indicated or calculated..     

A Spectroscopic Study of an Anhydrous Tetraethyl Orthosilicate-Boric Acid-Ethanol System

Hydrolysis and condensation reactions in an anhydrous sol-gel system comprising tetraethyl orthosilicate (TEOS, Si(OC2H5)4), boric acid (H3BO3) and ethanol have been studied using X-ray diffraction and NMR spectroscopy, and similarities and differences with the more traditional aqueous system are discussed. Boric acid is able to hydrolyse TEOS directly, and subsequent condensation reactions form borosiloxane (=B–O–Si) and siloxane (Si–O–Si) linkages. In an aqueous system, borosiloxanes are unstable to hydrolysis and are formed only upon heat treatment of the gel, a restriction avoided with anhydrous conditions. The anhydrous mixture is stable indefinitely against gelation, but can be readily gelled by addition of NaOH in ethanol. This system may be useful for preparing borosilicate glasses at lower temperatures with good homogeneity.     

Boron oxide encapsulated Bridgman growth of high-purity high-resistivity cadmium telluride crystals

High-purity semi-insulating CdTe crystals have been successfully grown by encapsulated (B₂O₃) Bridgman technique. The procedure strongly limits component losses allowing the achievement of stoichiometry control material and keeps a low level of impurity contamination as shown by mass spectroscopy analysis data. When strictly stoichiometry-controlled and high-purity polycrystalline source material has been used, high-resistivity crystals have been obtained without any intentional doping. EPD values in the range of 1–3×10⁴ cm⁻² have been observed in a wide region of the crystals. Luminescence spectroscopy confirms the purity and good structural quality of the material. The proposed method avoids the technical problems posed by the High Pressure Bridgman technique and fits the requirements for CdTe/CdZnTe crystals large-scale production.     

An Efficient and Facile Synthesis of 5‐(Thiophene‐2‐carbonyl)‐6‐(trifluoromethyl)‐tetrahydro‐pyrimidin‐2(1H)‐one and 6‐(Thiophen‐2‐yl)‐4,5‐dihydropyrimidin‐2(1H)‐one from Same Substrates Under Different Conditions

A series of 5‐(thiophene‐2‐carbonyl)‐6‐(trifluoromethyl)‐tetrahydropyrimidin‐2(1H)‐one and 6‐(thiophen‐2‐yl)‐4,5‐dihydropyrimidin‐2(1H)‐one derivatives have been synthesized from the reactions of aromatic aldehydes, 4,4,4‐trifluoro‐1‐(thien‐2‐yl)butane‐1,3‐dione and urea under the different conditions with high yields. In this research, it was found that the p‐toluenesulfonic acid was an efficient catalyst for obtaining 5‐(thiophene‐2‐carbonyl)‐6‐(trifluoromethyl)‐tetrahydropyrimidin‐2(1H)‐one derivative. At the same time, solvent‐free and NaOH were the preferred conditions for the synthesis of 6‐(thiophen‐2‐yl)‐4,5‐dihydropyrimidin‐2(1H)‐one derivative. Moreover, because of short reaction time, excellent yields, simple setup, this research offered an efficient process for preparing these kind compounds.     

Lead‐Free,Blue Emitting Bismuth Halide Perovskite Quantum Dots

Lead halide perovskite quantum dots (QDs) are promising candidates for future lighting applications, due to their high quantum yield, narrow full width at half maximum (FWHM), and wide color gamut. However, the toxicity of lead represents a potential obstacle to their utilization. Although tin(II) has been used to replace lead in films and QDs, the high intrinsic defect density and oxidation vulnerability typically leads to unsatisfactory material properties. Bismuth, with much lower toxicity than lead, is promising to constitute lead‐free perovskite materials because Bi³⁺ is isoelectronic to Pb²⁺ and more stable than Sn²⁺. Herein we report, for the first time, the synthesis and optical characterization of MA₃Bi₂Br₉ perovskite QDs with photoluminescence quantum yield (PLQY) up to 12 %, which is much higher than Sn‐based perovskite nanocrystals. Furthermore, the photoluminescence (PL) peaks of MA₃Bi₂X₉ QDs could be easily tuned from 360 to 540 nm through anion exchange.