Construction of a cryogen‐free thermal desorption gas chromatographic system with off‐the‐shelf components for monitoring ambient volatile organic compounds

An automated gas chromatographic system aimed at performing unattended measurements of ambient volatile organic compounds was configured and tested. By exploiting various off‐the‐shelf components, the thermal desorption unit was easily assembled and can be connected with any existing commercial gas chromatograph in the laboratory to minimize cost. The performance of the complete thermal desorption gas chromatographic system was assessed by analyzing a standard mixture containing 56 target nonmethane hydrocarbons from C₂–C₁₂ at sub‐ppb levels. Particular attention was given to the enrichment efficiency of the C₂ compounds, such as ethane (b.p. = –88.6°C) and ethylene (b.p. = –104.2°C), due to their extremely high volatilities. Quality assurance was performed in terms of the linearity, precision and limits of detection of the target compounds. To further validate the system, field measurements of target compounds in ambient air were compared with those of a commercial total hydrocarbon analyzer and a carbon monoxide analyzer. Highly coherent results from the three instruments were observed during a two‐month period of synchronized measurements. Moreover, the phenomenon of opposite diurnal variations between the biogenic isoprene and anthropogenic species was exploited to help support the field applicability of the thermal desorption gas chromatographic method.     

Effect of the ultrasonic emitter on the distortion performance of the parametric array loudspeaker

The parametric array loudspeaker (PAL) is a type of directional loudspeaker that utilizes the nonlinear acoustic effect to create the audible sound in an ultrasonic beam. Due to this unusual sound principle, it is inevitable that nonlinear distortion is incurred in the sound transmission of the PAL. Numerous modulation methods aiming to reduce the nonlinear distortion have been developed on the basis of the Berktay’s far-field solution, but they often perform in an unexpected manner. The degraded practical performance has been credited to the inaccuracy of the Berktay’s far-field solution. In this paper, we demonstrate the effect of the ultrasonic emitter on the distortion performance of the PAL and suggest that the Berktay’s far-field solution remains to be a good model equation.     

Simultaneous determination of Repaglinide and Irbesartan in biological plasmas using micellar enhanced excitation-emission matrix fluorescence coupled with ATLD method

A highly sensitive and selective 3D excitation-emission fluorescence method has been proposed to rapidly quantify the combined antidiabetics Repaglinide(Re) and Irbesartan(Ir) in rat and human plasmas with the aid of second-order calibration method based on alternating trilinear decomposition(ATLD) method. Re and Ir with weak fluorescence can be endowed with strong fluorescent property by changing the microenvironment in samples and improving the fluorescence quantum yield by using an appropriate micellar enhanced surfactant. The enhanced excitation-emission matrix fluorescence of Re and Ir can be accurately resolved and can simultaneously attain the optimal concentration even in the presence of a potentially strong intrinsic fluorescence from complex biological matrices, such as rat and human plasmas, by using the ATLD method, which completely exploits the "second-order advantage". The average recoveries of Re and Ir obtained from ATLD with the factor number of 3(N=3) were 101.0%±4.3% and 99.1%±4.1% for rat plasma and 100.5%±5.4% and 97.1%±3.6% for human plasma. Several statistical methods, including Student's t-test, figures of merit, and elliptical joint confidence region, have been utilized to evaluate the accuracy of the proposed method. Results show that the developed method can maintain second-order advantage in simultaneous determinations of the weak fluorescent analytes of interest in different biological plasma matrices.     

In situ synchrotron PXRD investigation of fresh and aged Equisetum ramosissimum Desf. (horsetail grass)

As one of the oldest species, horsetail grass (Equisetum ramosissimum Desf.) is known as a living fossil plant, dating back to the Mesozoic era. Horsetail grass is also considered one of the most important sources of bio-silica due to its ability to accumulate high amounts of silica in all parts of the plant; various minerals can also be isolated by heat treatment. Fresh and aged horsetail grass stored for 2 years under ambient conditions was investigated by synchrotron powder X-ray diffraction (PXRD). Clear crystallites were not observed in a fresh sample stored at room temperature; surprisingly, high amounts of gypsum (CaSO₄·2H₂O) and syngenite (K₂Ca[SO₄]₂·H₂O) were observed in the 2-day dried and 2-year aged samples, respectively. However, crystalline silica materials were not observed. In addition, in situ thermal treatment of up to 700°C was applied to investigate the crystals and phase transitions by focusing the X-ray beam onto a single stem. In situ synchrotron PXRD revealed that dehydration occurred in gypsum in the 2-day dried sample with an increase in temperature to hemihydrate (CaSO₄·xH₂O, 0.5 ≤ x ≤ 0.8) and anhydrite (CaSO₄). On the other hand, syngenite was transformed to calciolangbeinite (K₂Ca₂[SO₄]₃) at high temperatures in 2-year aged horsetail grass.     

疑似蛇毒液样品的纳升级超高效液相色谱-高分辨质谱分析鉴定

针对5个疑似蛇毒毒液及其沾染样品,基于纳升级超高效液相色谱-四极杆-静电场轨道阱高分辨质谱（Nano LC-MS/HRMS）技术,结合尺寸排阻色谱分离,建立了一种蛋白质种类及物种归属的严格鉴定方法。5个样品经尺寸排阻色谱分离后均得到3个洗脱峰,分别冻干后以胰蛋白酶进行溶液内酶解处理并进行液相色谱-高分辨质谱分析鉴定。首先采用全扫描-数据依赖型MS/MS（Full MS/dd MS²）采集模式对样品中的肽段信息进行非靶向采集,依次与Swiss-Prot、蛇亚目（Serpentes）、游蛇科（Colubroidea）、眼镜蛇科（Elapidae）、眼镜蛇亚科（Elapinae）、眼镜蛇属（Naja）蛋白质数据库逐级收缩比对;再筛选符合肽谱匹配度、肽段错误发现率小于1%和特征肽段数目大于等于2的蛋白质,共鉴定到32种蛋白质均来自中华眼镜蛇（Naja atra）,可归属于Naja atra的10个家族,主要为三指毒素、金属蛋白酶、磷脂酶A2等。最后,采用平行反应监测模式选取每种蛋白质的两条特征肽段进行靶向验证,当两条特征肽段均满足“至少75%的y⁺和b⁺离子的Δm/z小于5 ppm”时,方认为鉴定到了样品中的某一蛋白质。最终鉴定出5个样品均含有Naja atra蛇毒。此鉴定方法研究系统、严格,可为蛇毒中毒司法鉴定以及毒药物研究等提供有效的技术支持。     

Organic Photovoltaic Catalyst with σ-π Anchor for High-Performance Solar Hydrogen Evolution

Efficient in situ deposition of metallic cocatalyst, like zero-valent platinum (Pt), on organic photovoltaic catalysts (OPCs) is the prerequisite for their high catalytic activities. Here we develop the OPC (Y6CO), by introducing carbonyl in the core, which is available to σ-π coordinate with transition metals, due to the high-energy empty π* orbital of carbonyl. Y6CO exhibits a stronger capability to anchor Pt species and reduce them to metallic state, resulting in more Pt⁰ deposition, relative to the control OPC without the central σ-π anchor. Single-component and heterojunction nanoparticles (NPs) employing Y6CO show enhanced average hydrogen evolution rates of 230.98 and 323.22 mmol h⁻¹ g_[OPC]⁻¹, respectively, under AM 1.5G, 100 mW cm⁻² for 10 h, and heterojunction NPs yield the external quantum efficiencies of ca. 10 % in 500–800 nm. This work demonstrates that σ-π anchoring is one efficient strategy for integrating metallic cocatalyst and OPC for high-performance photocatalysis.     

Strong stacking between FH--N hydrogen-bonded foldamers and fullerenes: formation of supramolecular nano networks

The stacking interactions between FH--N hydrogen-bonded foldamers 1-3, bis-foldamer 4, and tris-foldamer 5 and C(60) and C(70) are described. Compound 4 contains two folded units, which are connected by an isophthalamide linker, whereas 5 has a C(3)-symmetrical discotic structure, in which three folded units are connected by a benzene-1,3,5-tricarboxamide unit. UV/Vis, fluorescence, and NMR experiments have revealed that the foldamers or folded units strongly stack with fullerenes in chloroform. The (apparent) association constants of the respective complexes have been determined by a fluorescence titration method. The strong association is tentatively attributed to intermolecular cooperative fluorophenylpi and solvophobic interactions. A similar but weaker interaction has also been observed between an MeOH--N hydrogen-bonded foldamer and fullerenes. AFM studies have revealed that the surfaces of 3 and 4 show fibrous networks, while the surface of 5 shows particles. In sharp contrast, mixtures of 3 and 4 with C(60) have been shown to generate thinner separated fibrils, whereas a mixture of 5 and C(60) produces honeycomb-like nano networks, for which a columnar cooperative stacking pattern is proposed. The results demonstrate the usefulness of FH--N hydrogen-bonded folded structures in the construction of nanoscaled materials.     

The zeta potential of surface-functionalized metallic nanorod particles in aqueous solution

Metallic nanoparticles suspended in aqueous solutions and functionalized with chemical and biological surface coatings are important elements in basic and applied nanoscience research. Many applications require an understanding of the electrokinetic or colloidal properties of such particles. We describe the results of experiments to measure the zeta potential of metallic nanorod particles in aqueous saline solutions, including the effects of pH, ionic strength, metallic composition, and surface functionalization state. Particle substrates tested include gold, silver, and palladium monometallic particles as well as gold/silver bimetallic particles. Surface functionalization conditions included 11-mercaptoundecanoic acid (MUA), mercaptoethanol (ME), and mercaptoethanesulfonic acid (MESA) self-assembled monolayers (SAMs), as well as MUA layers subsequently derivatized with proteins. For comparison, we present zeta potential data for typical charge-stabilized polystyrene particles. We compare experimental zeta potential data with theoretically predicted values for SAM-coated and bimetallic particles. The results of these studies are useful in predicting and controlling the aggregation, adhesion, and transport of functionalized metallic nanoparticles within microfluidic devices and other systems.     

Base controlled polydiazeniumdiolation of 4-heptanone and a new water layer structure

In a stoichiometry-controlled reaction, nitric oxide adds to the enolate of 4-heptanone at ca. -23 degrees C to give mono-, bis-, or tris-diazeniumdiolate (-N2O2(-)) products: potassium 4-heptanone-3,3,5-tris(diazeniumdiolate) (1), potassium butanoate 2,2-bis(diazeniumdiolate) (2), and potassium butanoate 2-diazeniumdiolate (3). The diazeniumdiolate products are stable crystalline solids under ambient conditions and as solids exothermally decompose at high temperatures. Single-crystal X-ray data measured for the dihydrate 3 reveal a new layer aggregation, L4(4)8(8), as octameric water aggregates in a stair conformation which interacts minimally with the cation of the salt.     

Ag4L2 nanocage as a building unit toward the construction of silver metal strings

Self-assembly of AgNO 3 with the semirigid tetratopic ligands 1,2,4,5-tetrakis(benzoimidazol-1-ylmethyl)benzene (TBim) and 1,2,4,5-tetrakis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene (TDMBim) afforded compounds [Ag 4(mu 4-TBim) 2(mu 2-eta (2)-NO 3) 2](NO 3) 2. (1)/ 2CH 2Cl 2.2CH 3OH ( 1mu (1)/ 2CH 2Cl 2.2CH 3OH) and [(NO 3 (-)) subset{Ag 4(mu 4-TDMBim) 2}][Ag(NO 3) 2](NO 3) 2.CH 2Cl 2.CH 3OH.4H 2O ( 2.CH 2Cl 2.CH 3OH.4H 2O), respectively. The structures of 1 and 2 were characterized by single-crystal X-ray diffraction analysis. Both compounds adopt a M 4L 2-type tetragonal metalloprismatic cage structure, [Ag 4(mu 4-L) 2] (4+), with strong intramolecular silver-silver contacts. Compound 1 is a discrete species, while compound 2 is a novel infinite chainlike supramolecular array involving silver metal strings assembled from a [Ag 4(mu 4-L) 2] (4+) nanocage and silver linkages. Thermogravimetric analyses of 1. (1)/ 2CH 2Cl 2.2CH 3OH and 2.CH 3OH.4H 2O indicate that the Ag 4L 2-cage structures of 1 and 2 both are thermally stable up to 330 degrees C. Results from an in situ (1)H NMR study of AgNO 3 and TDMBim in different molar ratios unambiguously revealed the successive self-organization process, in which self-organization of the molecular cage takes place initially followed by crystallization of the corresponding supramolecular arrays with silver metal strings.