Tip‐enhanced Raman spectroscopy – an interlaboratory reproducibility and comparison study

Since its first experimental realization, tip‐enhanced Raman spectroscopy (TERS) has emerged as a potentially powerful nanochemical analysis tool. However, questions about the comparability and reproducibility of TERS data have emerged. This interlaboratory comparison study addresses these issues by bringing together different TERS groups to perform TERS measurements on nominally identical samples. Based on the spectra obtained, the absolute and relative peak positions, number of bands, peak intensity ratios, and comparability to reference Raman and surface‐enhanced Raman spectroscopy (SERS) data are discussed. Our general findings are that all research groups obtained similar spectral patterns, irrespective of the setup or tip that was used. The TERS (and SERS) spectra consistently showed fewer bands than the conventional Raman spectrum. When comparing these three methods, the spectral pattern match and substance identification is readily possible. Absolute and relative peak positions of the three major signals of thiophenol scattered by 19 and 9 cm⁻¹, respectively, which can probably be attributed to different spectrometer calibrations. However, within the same group (but between different tips), the signals only scattered by 3 cm⁻¹ on average. This study demonstrated the suitability of TERS as an analytical tool and brings TERS a big step forward to becoming a routine technique. Copyright © 2014 John Wiley & Sons, Ltd.     

Facile and Convenient Synthesis of 5-Arylalkylidenerhodanines by Electrocatalytic Crossed Aldol Condensation

Abstract

An electrochemically induced catalytic crossed Aldol condensation of one equivalent of rhodanine with various aromatic aldehydes and ketones in ethanol in an undivided cell in the presence of sodium bromide as an electrolyte results in the formation of the corresponding 5-arylalkylidenerhodanines in 80–96% yield with reactions in 40 min.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Hydrothermal Synthesis of Bismuth Sulfide (Bi2S3) Nanorods: Bismuth(III) Monosalicylate Precursor in the Presence of Thioglycolic Acid

Well-segregated bismuth sulfide (Bi₂S₃) nanorods with a high order of crystallinity have been successfully prepared from bismuth(III) monosalicylate [BiO(C₇H₅O₃)] by a simple hydrothermal reaction in H₂O at 180 °C. Bismuth(III) monosalicylate and thioglycolic acid act as the starting materials. The products were characterized by powder X-ray diffraction, Ultraviolet–Visible (UV–Vis) spectroscopy, transmission electron microscopy photoluminescence spectroscopy, and Fourier transform infrared spectra. The powder X-ray diffraction pattern shows the product belongs to the orthorhombic Bi₂S₃ phase. Their UV–Vis spectrum shows the absorbance at 328 nm, with its direct energy band gap of 2.6 eV. Bismuth salicylate, which is known to be a complex, may play a critical role as a precursor and a template for the growth of linear bismuth sulfide nanorods. Finally the influences of the reaction conditions are discussed and a possible mechanism for the formation of Bi₂S₃ nanorods is proposed.     

Zinc–aluminum layered double hydroxide as a nano-sorbent for removal of Reactive Yellow 84 dye from textile wastewater effluents

In this research, the zinc–aluminum layered double hydroxide (Zn–Al LDH) was synthesized and structurally and morphologically characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and N₂ adsorption–desorption techniques. The obtained nano-structured inorganic material was employed as an innovative nano-sorbent for separation of Reactive Yellow 84 (RY84) dye from aqueous solutions, which can be spectrophotometrically monitored at λ = 359 nm. The effect of several parameters such as type of interlayer anion in Zn–Al LDH structure, pH, sample flow rate, elution conditions, amount of nano-sorbent, sample volume and co-existing ions on the retention efficiency was investigated and optimized. The results showed that trace amounts of the RY84 could be retained using a column packed with 300 mg of the Zn–Al(NO₃ ^?) LDH at pH 8 and stripped by 2.5 mL of 3.0 mol L^?1 NaOH. Under the optimum experimental conditions, the limit of detection and the relative standard deviation were 0.04 μg mL^?1 and 1.8 %, respectively. The calibration graph using the presented solid phase extraction system was linear in the range of 0.15–1.5 μg mL^?1 with a correlation coefficient of 0.9982. The method was successfully applied to removal of RY84 from several textile wastewater effluents.     

Synthesis of Imidazo[1,2‐a]pyridines Using Fe3O4@SiO2 as an Efficient Nanomagnetic Catalyst via a One‐Pot Multicomponent Reaction

A one‐pot multicomponent synthesis of imidazo[1,2‐a]pyridine derivatives by using pyridin‐2‐amines, aldehydes, and terminal alkynes in the presence of a catalytic amount of silica‐supported iron oxide (Fe₃O₄@SiO₂) nanoparticles in refluxing EtOH in good‐to‐excellent yields is reported.     

Synthesis and evaluation of antiproliferative activity of substituted N-(9-oxo-9H-xanthen-4-yl)benzenesulfonamides

Several novel N-(9-oxo-9H-xanthen-4-yl)benzenesulfonamide derivatives were prepared as potential antiproliferative agents. The in vitro antiproliferative activity of the synthesized compounds was investigated against a panel of tumor cell lines including breast cancer cell lines (MDA-MB-231, T-47D) and neuroblastoma cell line (SK-N-MC) using MTT colorimetric assay. Etoposide, a well-known anticancer drug, was used as a positive standard drug. Among synthesized compounds, 4-methoxy-N-(9-oxo-9H-xanthen-4-yl)benzenesulfonamide (5i) showed the highest antiproliferative activity against MDA-MB-231, T-47D, and SK-N-MC cells. Furthermore, pentafluoro derivatives 5a and 6a exhibited higher antiproliferative activity than doxorubicin against human leukemia cell line (CCRF-CEM) and breast adenocarcinoma (MDA-MB-468) cells. Structure–activity relationship studies revealed that xanthone benzenesulfonamide hybrid compounds can be used for the development of new lead anticancer agents.     

Preparation of a trihydrazinotriazine-functionalized core-shell nanocatalyst as an extremely efficient catalyst for the synthesis of benzoxanthenes

In recent years, there is a high demand on utilizing heterogeneous nanocatalysts in organic synthetic routes because of their green approach, facile purification of the products, and reusability of the catalyst. Herein, we introduced trihydrazinotriazine (THDT)-coated Fe₃O₄@SiO₂ as a novel amino-functionalized magnetic nanocompostie. We fully characterized the nanocatalyst and proved the morphology and magnetic property of the nanoparticles by using essential analyses. The basic attribute of the amino-rich porous surface of the nanocomposite provides a desirable environment for enhancing various reaction conditions. To examine the applicability of the nanocatalyst in organic reactions, we synthesized several benzoxanthenes using Fe₃O₄@SiO₂-THDT nanocatalysts. The nanocomposite successfully improved the reaction conditions and provided the benzoxanthenes in an environmentally friendly procedure, which afforded product in excellent yields (80–96%) and reduced time. The nanomagnetic catalyst was easily recovered after each trial by using an external magnet. After six successive runs, the loss of catalytic activity of the nanocomposite was negligible. Finally, we propounded a plausible mechanism for the preparation of the benzoxanthenes derivatives using the THDT-functionalized core-shell magnetic nanocatalyst.     

Combining Ion Mobility Spectrometry with Hydrogen-Deuterium Exchange and Top-Down MS for Peptide Ion Structure Analysis

The gas-phase conformations of electrosprayed ions of the model peptide KKDDDDIIKIIK have been examined by ion mobility spectrometry (IMS) and hydrogen deuterium exchange (HDX)-tandem mass spectrometry (MS/MS) techniques. [M+4H]⁴⁺ ions exhibit two conformers with collision cross sections of 418 Ų and 471 Ų. [M+3H]³⁺ ions exhibit a predominant conformer with a collision cross section of 340 Ų as well as an unresolved conformer (shoulder) with a collision cross section of ~367 Ų. Maximum HDX levels for the more compact [M+4H]⁴⁺ ions and the compact and partially-folded [M+3H]³⁺ ions are ~12.9, ~15.5, and ~14.9, respectively. Ion structures obtained from molecular dynamics simulations (MDS) suggest that this ordering of HDX level results from increased charge-site/exchange-site density for the more compact ions of lower charge. Additionally, a new model that includes two distance calculations (charge site to carbonyl group and carbonyl group to exchange site) for the computer-generated structures is shown to better correlate to the experimentally determined per-residue deuterium uptake. Future comparisons of IMS-HDX-MS data with structures obtained from MDS are discussed with respect to novel experiments that will reveal the HDX rates of individual residues. Graphical Abstract

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Rapid Synthesis of 3‐Aminoimidazo[1,2‐a]Pyridines and Pyrazines

p‐Toluenesulfonic acid catalyzed the one‐pot, three‐component synthesis of 3‐aminoimidazo[1,2‐a]pyridines and pyrazines through a condensation reaction of a 2‐aminoazine, an aldehyde, and an isocyanide at room temperature. This methodology affords a number of 3‐aminoimidazo[1,2‐a]pyridines in reasonable yields and short reaction times without any significant optimization of the reaction conditions.     

Microwave‐Assisted Aromatization of 1,3,5‐Trisubstituted 2‐Pyrazolines by Bi(NO3)3 · 5H2O,as a Novel and Convenient Oxidizing Agent

Abstract

Bismuth(III) nitrate pentahydrate, Bi(NO₃)₃?·?5H₂O, has been used as a mild, efficient, and inexpensive oxidant for the oxidative aromatization of several 1,3,5‐trisubstituted 2‐pyrazolines to pyrazoles in acetic acid under microwave irradiation with good to excellent yields.