Effect of spatial configuration on adhesion of 1,2-disubstituted cyclohexane derivatives

Spatial configuration has a significant effect on chemical self-assembly. However, the importance of spatial configuration in supramolecular adhesive materials has been frequently ignored. In this study, the effects of the spatial configuration on cohesion and adhesion were investigated. Owing to the diversities of the chemical structures and assembly patterns, 1,2-disubstituted cyclohexane derivatives were used in this combined experimental and theoretical investigation. The self-sorting assembly of enantiopure isomers improved cohesion but had a negative effect on adhesion. In contrast, racemic mixtures displayed stronger adhesion effects. Moreover, it was proven that the cis-configuration was more favorable for supramolecular adhesion than the trans-counterpart. In addition, the influence of the spatial configuration of 1,2-disubstituted cyclohexane derivatives could be effectively mitigated by hydrogen bond donors or acceptors. The addition of natural acids yielded three-dimensional polymeric networks, in which the spatial configuration was not the decisive factor for supramolecular adhesion.     

Immunosensor for α-fetoprotein based on a glassy carbon electrode modified with electrochemically deposited N-doped graphene,gold nanoparticles and chitosan

The authors describe a voltammetric immunosensor with antibody immobilized on a glassy carbon electrode (GCE) modified with N-doped graphene (N-GS), electrodeposited gold nanoparticles (AuNPs) and chitosan (Chit). The preparation is simple and the thickness of the electrodeposited films can be well controlled. Due to the specific advantages of N-GS, AuNPs and Chit, the electrode has a large specific surface, improved conductivity, high stability. A new label-free immunosensor for the model antigen (alpha fetoprotein, AFP) detection was then designed by employing N-GS-AuNP-Chit as the antibody immobilization and signal amplification platform. Differential pulse voltammetry and electrochemical impedance spectroscopy were used for the characterization of the stepwise assembly process. Under the optimized conditions, at a typical working potential of +0.20 V (vs. SCE), and by using hexacyanoferrate as an electrochemical probe, the immunosensor has a detection limit as low as 1.6 pg mL^?1 and a linear analytical range that extends from 5 pg mL^?1 to 50 ng mL^?1. AFP was quantified in spiked human serum samples with acceptable precision.

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Graphical Abstract Schematic of sensitive and effective label-free electrochemical immunosensor for the detection of AFP based on N-GS-AuNP-Chit as signal amplification matrix.

     

Preparation and magnetic property of the composite of nitrogen-doped carbon nanotubes decorated with nickel nanoparticles

A magnetic composite of nitrogen-doped carbon nanotubes (CN_x) decorated with nickel nanoparticles was synthesized by a chemical precipitation and deoxidization method. The decorated CN_x were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The XRD pattern showed that CN_x, nickel nanoparticles and little nickel oxides coexisted in the composite, TEM observation indicated that nickel nanoparticles were highly dispersed on the outer walls of CN_x, Magnetic measurements by VSM demonstrated that the saturated magnetization and remanence of CN_x were improved, while the coercivity was lowered after decorating with nickel nanoparticles.     

An extension of the mean free path approach to X-ray absorption spectroscopy

In the partial electron yield (PEY) acquisition mode commonly used in X-ray absorption spectroscopy (XAS) both elastically and inelastically scattered electrons are acquired, the latter contribution dominating the detector signal. Hence, the majority of the inelastic scattering events will not result in signal attenuation as happens in the case of X-ray photoelectron spectroscopy (XPS). To determine the respective changes in the effective mean free paths (MFP) we have performed XPS and near edge X-ray absorption fine structure (NEXAFS) spectroscopy measurements for a series of self-assembled monolayers of alkanethiols on gold substrates. The length of the alkyl chain and, therefore, the film thickness was varied. In agreement with expectations, the obtained MFPs for the Au 4f photoelectrons and C_KLL Auger electrons in the PEY acquisition mode (with the respective inelastic contributions) exceed the corresponding values for the Au 4f and C_KLL electrons of the same kinetic energies in the constant final state acquisition mode. Furthermore, the effective PEY-MFP for the C_KLL Auger electrons increased with decreasing retarding voltage of the PEY detector, which correlates with the enhanced contribution of the inelastically scattered electrons in the acquired signal. The results obtained are of importance for the analysis of XAS spectra of thin organic films and polymers.     

Facile synthesis of blue-emitting carbon dots@mesoporous silica composite spheres

This paper reported a facile and effective approach towards high-efficient composite luminophores by embedding blue-emitting N-doped carbon dots into spherical SiO₂ matrix (CDs@SiO₂). Mesoporous silica microspheres (r-CDs@MSN) with strong luminescence were synthesized by removing CTAB templates in CDs@SiO₂ using reflux with acetone. The r-CDs@MSN possess a spherical morphology with smooth surface and a diameter of 130 nm, while it exhibits an excitation-independent blue emission peak at 440 nm with an internal quantum yield of 21.5%. BET result shows that the corresponding surface area and adsorption total pore volume are 156.27 m²/g and 0.682 cm³/g, which is suitable for the drugs loading and release. The results indicate that r-CDs@MSN might act as a potential fluorescent drug carrier.     

Analysis of surface and guided wave plasmon polariton modes in insulator–metal–insulator planar plasmonic waveguides

Theoretical and experimental study of the surface plasmon–polariton and guided wave plasmon polariton modes is presented for the Sapphire/Ag/Polycarbonate/Air structure. Theoretical results are obtained by solving complex multilayer eigenvalue equations as well as the reflectivity equation for this structure. It is proposed that the mode attenuation can be significantly reduced by inserting a low index dielectric buffer between the metal and the guiding dielectric layer. The dispersion and attenuation curves are generated. Both the surface plasmon and guided wave plasmon polariton modes are studied experimentally. The experimental values of the effective refractive indices agree well with the theoretical values. The electric field profiles are generated and used to examine the nature of modes. After optimization of various parameters the condition for low loss single mode guiding is obtained for the proposed structure. Effect of metal thickness on surface plasmon mode is also discussed. It is inferred that in a properly optimized plasmonic waveguide, the losses can be reduced by a factor of 4.     

Critical review of bio/nano sensors for arsenic detection

Detection of arsenic is a long-standing challenge in environmental analytical chemistry. In recent years, using biomolecules and nanomaterials for sensing arsenic has been growingly reported. In this article, this field is critically reviewed based on some recent fundamental understandings including interactions between arsenic and gold, thiol, and DNA aptamers. First, taking advantage of the adsorption of As(III) on noble metal surfaces such as silver and gold, sensors were developed based on surface enhanced Raman spectroscopy, electrochemistry and colorimetry. In addition, by functionalizing metal nanoparticles with thiol containing molecules, As(III) induced aggregation of the particles based on As(III)/thiol interactions. As(V) interacts with metal oxides strongly and competitive sensors were developed by displacing pre-adsorbed DNA oligonucleotides. A DNA aptamer was selected for As(III) and many sensors were reported based on this aptamer, although careful binding measurements indicated that the sequence has no affinity towards As(III). Overall, bio/nano systems are promising for the detection of arsenic. Future work on fundamental studies, searching for more specific arsenic binding materials and aptamers, incorporation of sensors into portable devices, and more systematic test of sensors in real samples could be interesting and useful research topics.     

Inhibition of mycotoxin deoxynivalenol generation by using selenized glucose

Selenized glucose can be easily prepared via the selenization reaction of glucose using in situ generated NaHSe as the selenization reagent. The technique has been industrialized to produce the chemical in kilogram scale, making it an easily available material in laboratory presently. The selenized glucose may be widely used as the starting material for the preparation of selenium-containing catalysts, as the organoselenium additive for feeds, and as the efficient selenium-enriched foliar fertilizers. In this work, we found that treating Fusarium graminearum, a fungal pathogen inciting wheat scab disease, with selenium glucose could significantly inhibit the generation of the deoxynivalenol (DON) toxin, which might be a breakthrough for reducing the detriment of the wheat scab disease.     

Two-photon dual-channel fluorogenic probe for in situ imaging the mitochondrial H2S/viscosity in the brain of drosophila Parkinson’s disease model

H₂S is an essential gas signal molecule in cells, and viscosity is a key internal environmental parameter. Recent studies have shown that H₂S acts as a cytoarchitecture agent and gas transmitter in many tissues, e.g., as a regulator of neuroendocrine in the brain for mediating vascular tone in blood vessels. Mitochondrial viscosity is an important parameter for judging whether mitochondrial function is normal. It has been reported that oxidative stress and mitochondrial dysfunction are connected with Parkinson’s disease (PD), and the protective role of H₂S in PD models has been extensively demonstrated. Herein, Mito-HS, a new two-photon fluorescent probe was demonstrated to detect cross-talk between the two channels of mitochondrial viscosity and H₂S content. Moreover, this probe could detect the relative amount of and changes in mitochondrial H₂S in situ due to the reduced mitochondrial targeting ability after reaction with H₂S. The results show that H₂S in mitochondria is inversely related to viscosity. The PD model has a lower H₂S in mitochondria and a higher mitochondrial viscosity than did the normal. This result is important for our deep understanding of PD and its causes.     

A highly stable black phosphorene nanocomposite for voltammetric detection of clenbuterol

A nanocomposite was prepared from graphene-like two-dimensional black phosphorene (BP, an allotrope of phosphorus) and nafion (Nf) treated with isopropanol (IP). A glassy carbon electrode (GCE) modified with this nanocomposite was found to be a viable sensor for voltammetric determination of clenbuterol (CLB). Unlike previously reported pure BP, the BP nanocomposite was stable towards water and oxygen. Its morphology, structure, electrochemically active surface area and electrochemical stability were investigated. The BP-Nf (IP) modified GCE displayed good electrochemical stability and electrocatalytic capacity with a low working potential of 0.94 V (vs. SCE), excellent peak current response for CLB in a linear concentration range of 0.06–24 μM with a detection limit of 3.7 nM (3σ/m) and a sensitivity of 0.14 μA·μM^?1·cm^?2 under optimal conditions. A sensing mechanism for the electro-oxidation of CLB was suggested and verified by density functional theory calculations under imitation of aqueous solution conditions. The sensor was successfully applied to the determination of CLB in bovine meat and bovine serum samples.

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Graphical abstract Highly-stable black phosphorene (BP) nanocomposite based on Nafion (Nf) was used to modify a glassy carbon electrode (GCE). It is shonw to be a viable electrochemical platform for sensitive voltammetric determination of trace clenbuterol (CLB) in bovine beef and bovine serum.