Energy distributions of CO produced in an acetone-containing discharge

Tunable infrared diode laser absorption (TDLAS) and Fourier transform infrared absorption spectroscopies (FTIR) have been utilized to characterize the translational, rotational and vibrational distributions of CO in an acetone/argon DC plasma at total pressures ranging from 4 to 5 Torr and currents of 0.1–0.3 A. A broad vibrational distribution of CO was observed with gradually decreasing intensities from the fundamental band to v=12←11. When nitrogen was added to the plasma, the distribution is narrower, due to the efficient energy transfer between CO and N₂ molecules. The measured translational temperature in such plasmas ranged from 400–550 K. The rotational distribution can generally be fitted to a Boltzmann distribution within each vibrational level although the rotational temperature is highest for the lowest vibrational quantum number.     

BaIr0,67Be0,33O3: Eine stabilisierte kubische Form von BaIrO3

Inhaltsübersicht. Es ist gelungen, ein durch BeO stabilisiertes Bariumoxoiridat der Zusammensetzung BaIr_0,67Be_0,33O₃ in der Kristallform eines kubischen Perowskits mit kleiner Elementarzelle erstmals darzustellen. Raumgruppe O¹_h–Pm3m, a = 4,1009 Å, Z = 1. Ir⁵⁺ und Be² + besetzen die Oktaederposition des Perowskits statistisch. BaIr_0,67Be_0,33O₃: A Stabilized Cubic Form of BaIrO₃ For the first time it was possible to prepare a new barium-oxoiridate of the formula BaIr_0,67Be_0,33O₃, stabilized by BeO. It crystallizes in a small cubic unit cell of the perovskite type. Space group O¹_h–Pm3m; a = 4.1009 Å; Z = 1. Ir⁵⁺ and Be²⁺ occupy the octahedra positions of the perovskite structure statistically.     

International comparison of the determination of cadmium and lead in herb: the Comité Consultatif pour la Quantité de Matière (CCQM) pilot study CCQM-P97

A Comité Consultatif pour la Quantité de Matière (CCQM) inter-laboratory comparison program, CCQM-P97, for the analysis of cadmium and lead in Herba Demodii Styracifolii was organized by the Hong Kong Government Laboratory. The objective of the program was to establish comparability of trace metals analysis in herbal matrices amongst the participating national metrology institutes. The arithmetic mean values of the 13 participants were 0.3186 mg kg⁻¹ (RSD = 11.3%) and 1.650 mg kg⁻¹ (RSD = 11.0%) for cadmium and lead, respectively. The participants using double-isotope dilution mass spectrometry technique for their quantification were found to provide similar mean values to those of non-isotope dilution mass spectrometry users. The observation indicated that trace metal analysis in herbal matrices was not method-dependent, but the use of the highest metrological IDMS approach gave a better precision than other routine calibration methods.     

Patterning of robust self-assembled n-type hexaazatrinaphthylene-based nanorods and nanowires by microcontact printing

The one-dimensional (1-D) self-assembly property of an n-type hexaazatrinaphthylene (HATNA) discotic pi-conjugated molecule was studied. Structurally robust unimolecular columnar stacks of HATNA with tunable length have been fabricated through a combination of supramolecular self-assembly and post-polymerization approach. Moreover, microcontact printing can be utilized to transfer the self-assembled nanostructures to the surface to create desired functional patterns.     

High-throughput determination of seven trace elements in food samples by inductively coupled plasma-mass spectrometry

A method was developed for high-throughput determinations of 7 elements in food samples, namely antimony (Sb), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), and tin (Sn). The samples were digested by closed-vessel microwave-assisted digestion using concentrated nitric acid (HNO3) as the medium, followed by microwave- assisted evaporation to concentrate the sample solutions before dilution to the desired volume. The microwave-assisted evaporation procedure effectively reduced the final acid concentration to around 8% before analysis by inductively coupled plasma-mass spectrometry (ICP-MS). This reduction allows determination by ICP-MS to proceed without further sample dilution, which would affect the detection limit. The method was validated, and method recoveries for As, Cd, Cr, Pb, and Hg were within the certified ranges of the chosen certified reference materials. Recoveries of the 7 elements from spiked samples ranged from 93.1 to 103.6%. The standard uncertainties of precision for the 7 elements were between 3.1 and 4.3%. Interlaboratory comparison studies for As, Cd, and Pb gave z-scores ranging from -0.2 to 0.3.     

Core-shell and hollow nanocrystal formation via small molecule surface photodissociation; Ag@Ag2Se as an example

Metallic Ag nanoparticles have been converted to Ag2Se nanoparticles at ambient temperature and open atmosphere by UV photodissociation of adsorbed CSe2 on the Ag core surface. The photolysis could be prevented at any stage yielding Ag@Ag2Se core-shell structures of different thickness. Depending on the initial Ag nanoparticle size, either hollow or filled nanocrystals of Ag2Se could be prepared. The Kirkendall effect has been proposed to account for the formation of hollow nanoparticles. A coated-sphere Drude model has been used to explain the redshift of the Ag plasmon band as a function of the Ag2Se shell thickness as well as to provide the first estimates of the wavelength-dependent dielectric function of Ag2Se. This photochemical method might be especially promising for carrying out a direct room-temperature phototransformation of metallic into semiconductor nanostructures already assembled on surface templates.     

FTIR studies on the gas phase laser-induced decomposition of CF3CH2ONO

The unimolecular decomposition of CF₃CH₂O (2,2,2-trifluoroethoxy) radical generated from 355 nm pulsed nanosecond laser photolysis of CF₃CH₂ONO (2,2,2-trifluoroethylnitrite) in the gas phase has been studied using Fourier transform infrared absorption spectroscopy. The radical preferentially dissociates via its C–H bond cleavage to yield CF₃CHO (trifluoroacetaldehyde) as the major product. The infrared spectrum of formaldehyde, one of the products of C–C bond dissociation of CF₃CH₂O was not observed under a range of nitrite and argon buffer gas pressures. Similar results were obtained when thermal heating and broadband xenon lamp irradiation of the nitrite were carried out. The addition of high pressures of NO further decreased the production of CF₃CHO since recombination of NO with the trifluoroethoxy radical competes with the unimolecular dissociation process. Surprisingly, CF₃CDO was also the only product observed when the deuterated species CF₃CD₂ONO was photolysed by the 355 nm laser. These observations contradicted MP2/aug-cc-pVTZ calculations which were found to favour the C–C bond dissociation channel. However, 355 nm photolysis of CF₃CH₂ONO in the presence of O₂ yielded trifluoroethylnitrate, CF₃CH₂ONO₂ as the main product while CF₃CHO and CF₂O were also observable at much lower yields.     

Synthesis of indole based novel small molecules and their in vitro anti-proliferative effects on various cancer cell lines

Indole based novel small molecules were designed as potential anticancer agents. Multi step synthesis of these compounds was carried out by using Pd/C–Cu mediated coupling–cyclization strategy as a key step. The single crystal X-ray diffraction study was used to confirm the molecular structure of a representative compound unambiguously. Many of these compounds were evaluated for their anti-proliferative properties in vitro against six cancer cell lines as well as noncancerous cells. All these compounds showed selective growth inhibition of cancer cells and several of them were found to be promising with IC₅₀ values in the range of 0.1–1.2 μM, comparable to the known anticancer drug doxorubicin.     

聚{11-[(4'-正庚氧基-4-联苯基)羰基]氧-1-十一炔}的相结构与相转变

采用示差扫描量热法(DSC)、一维(1D)、二维(2D)广角X-射线衍射(WAXD)和偏光显微镜(PLM)等研究手段对聚{11-[(4'-正庚氧基-4-联苯基)羰基]氧-1-十一炔}(PA-9,7)的本体相转变和相结构进行研究,并采用分子动力学方法对相结构进行模拟.结果表明,样品的相转变为近晶B相(SmB)(→)近晶A相(SmA)(→)各向同性态(Iso).在近晶B相中,侧链在层状结构中排列成具有六次对称性的准长程有序结构.     

Coulombic interactions on the deposition and rotational mobility distributions of dyes in polyelectrolyte multilayer thin films

We employed negatively charged fluorescein (FL), positively charged rhodamine 6G (R6G), and neutral Nile Red (NR) as molecular probes to investigate the influence of Coulombic interaction on their deposition into and rotational mobility inside polyelectrolyte multilayer (PEM) films. The entrapment efficiency of the dyes reveals that while Coulombic repulsion has little effect on dye deposition, Coulombic attraction can dramatically enhance the loading efficiency of dyes into a PEM film. By monitoring the emission polarization of single dye molecules in polyethylenimine (PEI) films, the percentages of mobile R6G, NR, and FL were determined to be 87 +/- 4%, 76 +/- 5%, and 68 +/- 3%, respectively. These mobility distributions suggest that cationic R6G enjoys the highest degree of rotational freedom, whereas anionic FL shows the least mobility because of Coulombic attraction toward cationic PEI. Regardless of charges, this high percentage of mobile molecules is in stark contrast to the 5-40% probe mobility reported from spun-cast polymer films, indicating that our PEI films contain more free volume and display richer polymer dynamics. These observations demonstrate the potential of using isolated fluorescent probes to interrogate the internal structure of a PEM film at a microscopic level.