A Metal-Based Receptor for Selective Coordination and Fluorescent Sensing of Chloride

A scorpionate Zn²⁺ complex, constituted by a macrocyclic pyridinophane core attached to a pendant arm containing a fluorescent pyridyl-oxadiazole-phenyl unit (PyPD), has been shown to selectively recognize chloride anions, giving rise to changes in fluorescence emission that are clearly visible under a 365 nm UV lamp. This recognition event has been studied by means of absorption, fluorescence, and NMR spectroscopy, and it involves the intramolecular displacement of the PyPD unit by chloride anions. Moreover, since the chromophore is not removed from the system after the recognition event, the fluorescence can readily be restored by elimination of the bound chloride anion.     

Application of ion-in-conjugation molecules in resistive memories and gas sensors: The role of conjugation

Ion-in-conjugation(IIC) materials are eme rging as an important class of organic electronic materials with wide applications in energy storage,resistive memories and gas sensors.Many IIC materials were designed and investigated,however the role of conjugation in IIC materials' performance is yet investigated.Here we designed two molecules obtained by condensation of 4-butylaniline and oxocarbon acid.Squaric acid derivatives squaraine named SA-Bu and a croconamide named CA-Bu which only differ in their oxocarbon cores.While employing SA-Bu and CA-Bu as resistive memory and gas sensory materials,SA-Bu has attained promising performance in ternary memo ry and detection of NO_2 as low as 10 parts-per-billion whereas CA-Bu show mainly binary memory behavior and negligible NO_2 response.Theoretical calculations reveal that conjugation of CA-Bu was distorted by the increased steric hindrance,frustrating the charge transport and suppressing the conductivity.Our work demonstrates that the conjugation plays a crucial role in ion-in-materials promoting ternary RRAM devices and highperformance gas sensors manufacture.     

Chromatographic behavior of selected dyes on silica and cellulose micro-TLC plates: Potential application as target substances for extraction,chromatographic, and/or microfluidic systems

ABSTRACT

The main goal of this research communication focuses on screening of chromatographic behavior of 18 colorants including amaranth, black PN, bromophenol blue, bromocresol green, bromocresol purple, bromothymol blue, carmine, dimethyl yellow, erythrosine, fluorescein, methyl red, naphthalene black, patent blue, phenol red, Sudan II, Sudan III, Sudan IV, and p-xylenol blue. They are commonly used as food and industrial colorants or sensing molecules for analytical and biomedical applications. We studied retention (R_F), peak base width (W_b), and peak asymmetry factor (A_S) data collected under thermostatic conditions (303?K) using silica and cellulose-coated microplates (5?×?5?cm) and simple as possible mono/binary eluents. Presented retention database may help to select the proper conditions for, for example, chromatographic separation, extraction to solid phase (e.g. bar-type extraction devices) or application of such chemicals as the internal standard substances for planar/column chromatography and/or microfluidic devices (e.g., microfluidic paper-based analytical devices—μPADs). Furthermore, the microplates peak capacity (maximum number of resolvable spots, n) was calculated and discussed. As the second goal, we presented results of literature concerning dyes quantification in complex samples. We compared latest methodologies involving simple spectrophotometric analysis and more sophisticated protocols like high-throughput separation/detection procedures based on high-performance planar/liquid chromatography, capillary electrophoresis and microfluidic devices.     

The effect of the chemical,biological, and physical environment on quorum sensing in structured microbial communities

As researchers attempt to study quorum sensing in relevant clinical or environmental settings, it is apparent that many factors have the potential to affect signaling. These factors span a range of physical, chemical, and biological variables that can impact signal production, stability and distribution. Optimizing experimental systems to natural or clinical environments may be crucial for defining when and where quorum sensing occurs. These points are illustrated in our case study of S. aureus signaling in biofilms, where signal stability may be affected by the host environment. The basic signaling schemes have been worked out at the molecular level for a few of the major quorum-sensing systems. As these studies continue to refine our understanding of these mechanisms, an emerging challenge is to identify if and when the local environment can affect signaling.     

A sensitive fluorescence turn-on assay of bleomycin and nuclease using WS2 nanosheet as an effective sensing platform

As an important antitumor drug, bleomycin (BLM) is widely used in the treatment of a variety of cancers. In addition, nucleases play a crucial role in DNA replication, recombination and repair which are associated with cancer development. Thus, the development of BLM and nuclease detection methods is of great significance in cancer therapy and related biological mechanism research. Here, a WS₂ nanosheet-based turn-on fluorescent sensing platform for simple, fast and sensitive detection of BLM and nuclease was reported. WS₂ nanosheet exhibits different affinity toward ssDNA with different length and excellent fluorescence quenching ability. A fluorescein (FAM)-labeled long ssDNA could be adsorbed on the surface of WS₂ nanosheet and the fluorescence was therefore quenched. In the presence of BLM·Fe(II) or S1 nuclease (a ssDNA-specific nuclease which was used as a model enzyme), an irreversible scission of long ssDNA was underwent through the BLM-induced oxidation cleavage or S1 nuclease-induced enzymatic hydrolysis. Short FAM-linked oligonucleotide fragments which could not be adsorbed on the nanosheet surface were then produced, resulting in a weak fluorescence quenching after mixing WS₂ nanosheets. Thus, the fluorescence signal was restored. The proposed sensor displays a wide linear range and a high sensitivity with a detection limit of 0.3 nM for BLM and 0.01 U mL⁻¹ for S1 nuclease. It also exhibits a good performance in complex biological samples. This method not only provides a strategy for BLM or S1 nuclease assay but also offers a potential application in biomedical and clinical study.     

Large‐Area Alignment of Tungsten Oxide Nanowires over Flat and Patterned Substrates for Room‐Temperature Gas Sensing

Alignment of nanowires over a large area of flat and patterned substrates is a prerequisite to use their collective properties in devices such as gas sensors. In this work, uniform single‐crystalline ultrathin W₁₈O₄₉ nanowires with diameters less than 2 nm and aspect ratios larger than 100 have been synthesized, and, despite their flexibility, assembled into thin films with high orientational order over a macroscopic area by the Langmuir–Blodgett technique. Alignment of the tungsten oxide nanowires was also possible on top of sensor substrates equipped with electrodes. Such sensor devices were found to exhibit outstanding sensitivity to H₂ at room temperature.     

Non-Stationary Complementary Non-Uniform Sampling (NOSCO NUS) for Fast Acquisition of Serial 2D NMR Titration Data

NMR spectroscopy offers unique benefits for ligand binding studies on isotopically labelled target proteins. These benefits include atomic resolution, direct distinction of binding sites and modes, a lowest detectable affinity limit, and function independent setup. Yet, retracing protein signal assignments from apo to holo states to derive exact dissociation constants and chemical shift perturbation amplitudes (for ligand docking and structure-based optimization) requires lengthy titration series of 2D heteronuclear correlation spectra at variable ligand concentration that may exceed the protein's lifetime and available spectrometer time. We present a novel method to overcome this critical limitation, based on non-stationary complementary non-uniform sampling (NOSCO NUS) combined with a robust particle swarm optimization algorithm. We illustrate its potential in two challenging studies with very distinct protein sizes and binding affinities, showing that NOSCO NUS can reduce measurement times by an order of magnitude to make such highly informative NMR titration studies more broadly feasible.     

Structural Diversity in Luminescent MOFs Containing a Bent Electron‐rich Dicarboxylate Linker and a Flexible Capping Ligand: Selective Detection of 4‐Nitroaniline in Water

A combination of a bent bis(naphthalene) and hydroxy‐based dicarboxylate linker and a flexible bis(tridentate)polypyridyl ligand has been employed to self‐assemble with two different d¹⁰ metal centers, Zn^II and Cd^II, to form structurally diversified luminescent metal–organic frameworks, [Zn₂(tpbn)(mbhna)₂(H₂O)₂]?4 H₂O?1.5DMF ( 1 ) and {[Cd₂(tpbn)(mbhna)₂]?2DMF}_n ( 2 ), respectively (where, tpbn=N,N′,N′′,N′′′‐tetrakis(pyridine‐2‐ylmethyl)butane‐1,4‐diamine and H₂mbhna=4,4′‐methylene‐bis[3‐hydroxy‐2‐naphthalene carboxylic acid]). Both 1 and 2 are characterized and analyzed by various analytical techniques including single‐crystal X‐ray diffractometry. Their excellent emissive nature is studied in different solvents and further utilized to selectively detect aromatic amines, particularly 4‐nitroaniline in water with detection limits at sub‐ppm level. The difference in sensing activity of 1 and 2 toward 4‐NA is corroborated well with their structures. The mechanism of action has been established through Stern–Volmer plot, spectral overlap, time‐resolved lifetime studies and HOMO–LUMO energy calculations. In addition, 1 and 2 are found to be recyclable and display good stability after sensing experiments.     

Tailoring Coordination Polymers by Substituent Effect: A Bifunctional CoII‐Doped 1D‐Coordination Network with Electrochemical Water Oxidation and Nitroaromatics Sensing

Three Cd^II coordination polymers (CPs) were synthesized with a tripodal ligand N,N‘,N‘ ‘‐tris(4‐pyridinylmethyl)‐1,3,5‐benzenetricarboxamide in combination with three different substituted isophthalic acids with general formulas {[Cd₂( L )(NIP)₂(H₂O)₂].4H₂O}_n, (CP‐ 1 ), {[Cd₂( L )(AIP)₂(H₂O)₂].4H₂O}_n, (CP‐ 2 ) and {[Cd( L )(BIP) (H₂O)].4H₂O}_n, (CP‐ 3 ). The substituent groups on the co‐ligand had profound effect on the network topologies of the corresponding CPs as well as their properties. Out of the three, CP‐ 1 and 2 were found to form 3D networks whereas CP‐ 3 was a 1D linear chain with uncoordinated pyridyl sites. Due to its structural features CP‐ 3 was found to show interesting properties. The 1D CP containing uncoordinated pyridyl site exhibited an excellent ability for doping with Co^II which in turn acts as an efficient water oxidation electrocatalyst with required overpotential of 380 mV for an anodic current density of 1 mA cm^?2. The CP also exhibited luminescence‐based detection of nitroaromatics (LOD: 0.003 mm ) without any significant interference in presence of other organic compounds.