Towards Organic Zeolites and Inclusion Catalysts: Heptazine Imide Salts Can Exchange Metal Cations in the Solid State

Highly crystalline potassium (heptazine imides) were prepared by the thermal condensation of substituted 1,2,4- triazoles in eutectic salt melts. These semiconducting salts are already known to be highly active photocatalysts, e.g. for the visible light driven generation of hydrogen from water. Herein, we show that within the solid state structure, potassium ions can be exchanged to other metal ions while the crystal habitus is essentially preserved

Triazoles : a new class of precursors for the synthesis of negatively charged carbon nitride derivatives

Carbon nitride polymers were prepared for the first time by the pyrolysis of 3,5-disubstituted-1,2,4-triazole derivatives, namely 3,5-diamino-1,2,4-triazole [1] and 3-amino-1,2,4-triazole-5-thiol [2], in bulk as well as in LiCl/KCl salt melts. The reaction of [1] and [2] in bulk yields condensed heptazine-based polymers, while in LiCl/KCl eutectics it leads to the formation of well-defined potassium poly(heptazine imides), according to the results of 13C NMR and XPS investi-gations, whose formation resembles that of emeraldine salts of polyaniline. The density functional calculations supported the structural model suggested for potassium poly(heptazine imide) polymer. Owing to the specific reaction path, the products obtained from triazoles therefore show electronic properties rather different to known carbon nitrides, such as band gap and conduction and valence bands positions. With the degree of crystallinity of the reference materials, triazole-derived carbon nitrides are characterized by almost complete absence of steady photoluminescence, charge separation and localization upon excitation seems to be improved. As a consequence, photocatalysts prepared from [2] outperform classical carbon nitrides in a model dye degradation reaction and mesoporous graphitic carbon nitride in hydrogen evolution reaction under visible light irradiation. On its turn, [1] can be conveniently used as a co-monomer in order to prepare carbon nitrides with improved visible light absorption

Nanohybrid biosensor based on mussel-inspired electro-cross-linking of tannic acid capped gold nanoparticles and enzymes

Complementary tools to classical analytical methods, enzymatic biosensors are widely applied in medical diagnosis due to their high sensitivity, potential selectivity, and their possibility of miniaturization/automation. Among the different protocols of enzyme immobilization, the covalent binding and cross-linking of enzymes ensure the great stability of the developed biosensor. Obtained manually by drop-casting using a specific cross-linker, this immobilization process is not suitable for the specific functionalization of a single electrode out of a microelectrode array. In the present work, we developed a nanohybrid enzymatic biosensor with high sensitivity by a mussel-inspired electro-cross-linking process using a cheap and abundant natural molecule (tannic acid, TA), gold salt, and native enzymes. Based on the use of a cheap natural compound and gold salt, this electro-cross-linking process based on catechol/amine reaction (i) is versatile, likely to be applied on any kind of enzymes, (ii) does not require the synthesis of a specific cross-linker, (ii) gives enzymatic biosensors with high and very stable sensitivity over two weeks upon storage at room temperature and (iv) is temporally and spatially controlled, allowing the specific functionalization of a single electrode out of a microelectrode array. Besides the development of microbiosensors, this process can also be used for the design of enzymatic biofuel cells

Tridimensional few-layer graphene-like structures from sugar-salt mixtures as high-performance supercapacitor electrodes

© 2018 Elsevier Ltd This work describes a straightforward approach to the production of highly-performing and cost-effective C-based materials for energy storage application while proposing an original and effective method to the control of the final material morphology. Indeed, robust few-layer graphene-like and highly open-cell structures have been prepared by a modified chemical activation procedure starting from costless sugar/salt mixtures. The as-prepared C-samples ensure high ion-accessible surface area and low ion transport resistance, two key features for the fabrication of effective electrochemical double layer supercapacitors. A selected sample from this series exhibits high specific capacitance (Cg) (312 and 234 F g−1 at 0.5 and 50 A g−1, respectively, in 0.5 M H2SO4), particularly at high current density values, along with excellent cycling stability and Cg retention for increasing charge–discharge rates

Biochemical applications of surface-enhanced infrared absorption spectroscopy

An overview is presented on the application of surface-enhanced infrared absorption (SEIRA) spectroscopy to biochemical problems. Use of SEIRA results in high surface sensitivity by enhancing the signal of the adsorbed molecule by approximately two orders of magnitude and has the potential to enable new studies, from fundamental aspects to applied sciences. This report surveys studies of DNA and nucleic acid adsorption to gold surfaces, development of immunoassays, electron transfer between metal electrodes and proteins, and protein–protein interactions. Because signal enhancement in SEIRA uses surface properties of the nano-structured metal, the biomaterial must be tethered to the metal without hampering its functionality. Because many biochemical reactions proceed vectorially, their functionality depends on proper orientation of the biomaterial. Thus, surface-modification techniques are addressed that enable control of the proper orientation of proteins on the metal surface. [Figure: see text