Mechanical Properties of Single-Crystal Calcite and Their Temperature and Strain-Rate Effects.

Calcite is the most stable crystalline phase of calcium carbonate. It is applied or found in composite products, the food industry, biomineralization, archaeology, and geology, and its mechanical properties have attracted more and more attention. In this paper, the mechanical behaviors of single-crystal calcite under uniaxial tension in different directions were simulated with the molecular dynamics method. The obtained elastic moduli are in good agreement with the experimental results. It has been found from further research that single-crystal calcite has typical quasi-brittle failure characteristics, and its elastic modulus, fracture strength, and fracture strain are all strongly anisotropic. The tensile failure is caused by dislocation emission, void formation, and phase transition along the [010] and [421] directions, but by continuous dislocation glide and multiplication along the [421¯] direction. The fracture strength, fracture strain, and elastic modulus are all sensitive to temperature, but only elastic modulus is not sensitive to strain rate. The effects of temperature and logarithmic strain rate on fracture strength are in good agreement with the predictions of fracture dynamics.

Facile synthesis of Ag-niobium ditelluride nanocomposites for the molecular fingerprint analysis of muscle tissues.

The surface-enhanced Raman scattering (SERS) technique has attracted increasing attention in biomedicine due to the capability of providing the molecular fingerprint information of biosamples. Two-dimensional (2D) metal nanohybrids have proven to be efficient SERS substrates for bioanalysis due to the cooperative Raman enhancement mechanism. Herein, a facile strategy for the fabrication of a novel transition metal telluride-based 2D-metal SERS substrate is proposed. Ag-niobium ditelluride (NbTe2) nanocomposites are synthesized through in situ reduction of Ag nanoparticles on NbTe2 nanosheets (NSs). The excellent SERS performance of Ag-NbTe2 NSs probably originates from the coupling effect of enhanced electromagnetic field distribution around the plasmonic nanostructure (hot spots) and the charge transfer caused by the semiconductor material after numerical simulations. Using Ag-NbTe2 NSs as an ultrasensitive SERS probe, the molecular components of three types of muscle tissues are clearly identified. An effective classification of skeletal, cardiac and smooth muscles is also realized according to their SERS data plus principal component analysis. In addition, the monitoring of the skeletal muscle stretching process is achieved by the Ag-NbTe2 NS-based SERS analysis, which represents a powerful tool for molecular exercise physiology.