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101.
We study the nature of the smectic–isotropic phase transition using a mobile 6-state Potts model. Each Potts state represents a molecular orientation. We show that with the choice of an appropriate microscopic Hamiltonian describing the interaction between individual molecules modeled by a mobile 6-state Potts spins, we observe the smectic phase dynamically formed when we cool the molecules from the isotropic phase to low temperatures (T). In order to elucidate the order of the transition and the low-T properties, we use the high-performance Wang–Landau flat energy-histogram technique. We show that the smectic phase goes to the liquid (isotropic) phase by melting/evaporating layer by layer starting from the film surface with increasing T. At a higher T, the whole remaining layers become orientationally disordered. The melting of each layer is characterized by a peak of the specific heat. Such a succession of partial transitions cannot be seen by the Metropolis algorithm. The successive layer meltings/evaporations at low T are found to have a first-order character by examining the energy histogram. These results are in agreement with experiments performed on some smectic liquid crystals. 相似文献
102.
The task of reconstructing the system’s state from the measurements results, known as the Pauli problem, usually requires repetition of two successive steps. Preparation in an initial state to be determined is followed by an accurate measurement of one of the several chosen operators in order to provide the necessary “Pauli data”. We consider a similar yet more general problem of recovering Feynman’s transition (path) amplitudes from the results of at least three consecutive measurements. The three-step histories of a pre- and post-selected quantum system are subjected to a type of interference not available to their two-step counterparts. We show that this interference can be exploited, and if the intermediate measurement is “fuzzy”, the path amplitudes can be successfully recovered. The simplest case of a two-level system is analysed in detail. The “weak measurement” limit and the usefulness of the path amplitudes are also discussed. 相似文献
103.
Novel highly sensitive chiral organic field-effect transistors(COFET)were developed by directly assembling imidazolium3,5-dimethylphenylcabamoylated-β-cyclodextrin(lm^+-Ph-β-CD)and 3,5-dimethylphenylcarbamoylated-β-CD(Ph-β-CD)respectively onto the semiconductor layer as sensing units.The Im+-Ph-β-CD/COFET afforded better enantioselectivity and a lowest detection concentration of10^-18 L/mol as well as the potentiality in quantitative analysis of commercial medicines. 相似文献
104.
Yueyue Li Yanan Ban Ruihui Wang Zheng Wang Zhanxian Li Chenjie Fang Mingming Yu 《中国化学快报》2020,31(2):443-446
A ratiometric fluorescent hybrid nanoprobe CDs-1 for arginine(Arg),exhibiting high sensitivity(the limit of detection,LOD,being 6.5×10^-8 mol/L) and excellent selectivity and anti-interference ability,was fabricated through fluorescence resonance energy transfer(FRET) and the electrostatic attraction between positively-charged hemicyanine molecules and negatively-charged carbon dots(CDs).Arg can be quantitatively detected in the concentration range from 6.0×10^-5 mol/L to 2.7×10^-4 mol/L.Further,due to its ability to target mitochondrion and low cytotoxicity,intracellular Arg was succes s fully tracked through ratiometric fluorescence imaging. 相似文献
105.
Magnetic nature carbon dots (MNCDs) are fast growing materials with extremely unique physico-chemical properties and physiological ability to extend their applications from separation science to detection and bio-/magnetic resonance imaging applications. Recent studies have revealed that the MNCDs are significantly used as promising agents in analytical chemistry for the separation and identification of trace level target analytes. Further, the MNCDs have been used as probes for bioimaging of cells and magnetic resonance imaging (MRI) of tumors. Due to the lack of comprehensive reviews in this emerging field especially MNCDs applications in analytical chemistry, this review may provide quick guide and reference on the MNCDs-based analytical approaches for the separation and detection of trace level analytes, and bio- and MR- imaging of various cells. In this review article, we will summarize the synthetic approaches for the fabrication of MNCDs. The main part of this proposed review is devoted to the tremendous applications of MNCDs (Fe3O4@CDs, metal ion (Fe3+, Mn2+, Co2+ and Gd2+)-doped CDs, MnO2@CDs) in analytical chemistry from separation science to detection and bio- and MR imaging. Finally, we will explore the challenges and future prospects of magneto fluorescent carbon dots in biomedical applications. 相似文献
106.
107.
Dr. Victor de Seauve Dr. Marie-Angélique Languille Dr. Mathieu Kociak Dr. Stéphanie Belin Dr. James Ablett Prof. Christine Andraud Prof. Odile Stéphan Dr. Jean-Pascal Rueff Dr. Emiliano Fonda Prof. Bertrand Lavédrine 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9198-9204
The first colour photographs were created by a process introduced by Edmond Becquerel in 1848. The nature of these photochromatic images colours motivated a debate between scientists during the XIXth century, which is still not settled. We present the results of chemical analysis (EDX, HAXPES and EXAFS) and morphology studies (SEM, STEM) aiming at explaining the optical properties of the photochromatic images (UV-visible spectroscopy and low loss EELS). We rule out the two hypotheses (pigment and interferences) that have prevailed since 1848, respectively based on variations in the oxidation degree of the compound forming the sensitized layer and periodically spaced photolytic silver planes. A study of the silver nanoparticles dispersions contained in the coloured layers showed specific localizations and sizes distributions of the nanoparticles for each colour. These results allow us to formulate a plasmonic hypothesis on the origin of the photochromatic images colours. 相似文献
108.
Xiangtang Li Ruichuan Yin Hang Hu Yingju Li Prof. Xiaofei Sun Prof. Sudhansu K. Dey Prof. Julia Laskin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(50):22574-22577
Ambient ionization based on liquid extraction is widely used in mass spectrometry imaging (MSI) of molecules in biological samples. The development of nanospray desorption electrospray ionization (nano-DESI) has enabled the robust imaging of tissue sections with high spatial resolution. However, the fabrication of the nano-DESI probe is challenging, which limits its dissemination to the broader scientific community. Herein, we describe the design and performance of an integrated microfluidic probe (iMFP) for nano-DESI MSI. The glass iMFP, fabricated using photolithography, wet etching, and polishing, shows comparable performance to the capillary-based nano-DESI MSI in terms of stability and sensitivity; a spatial resolution of better than 25 μm was obtained in these first proof-of-principle experiments. The iMFP is easy to operate and align in front of a mass spectrometer, which will facilitate broader use of liquid-extraction-based MSI in biological research, drug discovery, and clinical studies. 相似文献
109.
Dr. Chenge Li Dr. Alison G. Tebo Marion Thauvin Marie-Aude Plamont Prof. Dr. Michel Volovitch Dr. Xavier Morin Prof. Dr. Sophie Vriz Prof. Dr. Arnaud Gautier 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18073-18079
Far-red emitting fluorescent labels are highly desirable for spectral multiplexing and deep tissue imaging. Here, we describe the generation of frFAST (far-red Fluorescence Activating and absorption Shifting Tag), a 14-kDa monomeric protein that forms a bright far-red fluorescent assembly with (4-hydroxy-3-methoxy-phenyl)allylidene rhodanine (HPAR-3OM). As HPAR-3OM is essentially non-fluorescent in solution and in cells, frFAST can be imaged with high contrast in presence of free HPAR-3OM, which allowed the rapid and efficient imaging of frFAST fusions in live cells, zebrafish embryo/larvae, and chicken embryos. Beyond enabling the genetic encoding of far-red fluorescence, frFAST allowed the design of a far-red chemogenetic reporter of protein–protein interactions, demonstrating its great potential for the design of innovative far-red emitting biosensors. 相似文献
110.
The electronic (energy gap and work function) as well as electrical properties (dipole moment, polarizability, and first hyperpolarizabilities) of the first-row transition metals decorated C24N24 cavernous nitride fullerene were explored using DFT calculations. The transition metals are decorated at N4 cavity of C24N24 fullerene. According to our spin polarized computations, the most stable spin state monotonically increases to sextet for Mn@C24N24 and thereafter dropped off gradually to singlet state for Zn@C24N24 system. The findings demonstrate that transition metals can remarkably decrease the HOMO-LUMO energy gap and work function values up to 63% and 21% of bare C24N24, respectively. As can be seen, when the Sc and Ti metals are located above the N4 cavity of fullerene, systems of enhanced static hyperpolarizabilities (β0) are delivered. These findings might provide an effective strategy to design high performance eletcro-optical materials based on carbon- nitride fullerene. 相似文献