The spectrally and temporally resolved luminescence of three-dimensional (3D) InGaN/GaN microrods and planar light emitting diode (LED) structures is studied for different energy densities of fs-laser excitation pulses and for different sample temperatures. We find an energy density threshold above which irreversible modifications of the structures take place, which leads to a decrease of the luminescence intensity and a change in the intensity ratio of the GaN to the InGaN luminescence. Due to the quantum confined Stark effect, a biexponential decay characteristic is found in the planar structure, while the 3D microrods with nonpolar InGaN quantum wells on their sidewalls show a monoexponential decay of the InGaN luminescence. For both structures, the decay of the luminescence becomes faster with increasing energy density per pulse. However, the luminescence of the planar LED decays faster with increasing temperature, while the opposite trend is found for the 3D sample.

Organic molecular crystals are often noncubic and contain significant steric hindrance within their structure to resist dislocation motion. Plastic deformation in these systems can be imparted during processing (tableting and comminution of powders), and the defect density impacts subsequent properties and performance. This study measured the elastic and plastic properties of representative monoclinic, orthorhombic, and triclinic molecular crystalline structures using nanoindentation of as-grown sub-mm single crystals. The variation in modulus due to in-plane rotational orientation, relative to a Berkovich tip, was approximately equal to the variation of a given crystal at a fixed orientation. The onset of plasticity occurs consistently at shear stresses between 1 and 5% of the elastic modulus in all three crystal systems, and the hardness to modulus ratio suggests conventional Berkovich tips do not generate fully self-similar plastic zones in these materials. This provides guidance for mechanical models of tableting, machining, and property assessment of molecular crystals.

Extremely hard, wear-resistant SiC-bonded diamond materials with diamond contents of approximately 45–60% by volume can be prepared by pressureless infiltration of shaped diamond compacts with silicon. Materials with diamond grain sizes in the range of 10–100 µm can be produced having a free silicon content of less than 5 vol%. Components with large dimensions can be prepared as graded or ungraded materials. Graded components are composed of silicon infiltrated SiC base material with diamond–SiC composite layers of 0.1 mm by dip coating technology to several mm in thickness by doubled die pressing in regions with high loading. This creates the possibility of producing low-cost, wear-resistant components of various geometries and dimensions with bending strengths of 400–500 MPa, hardness values of 48 GPa, and fracture toughness levels of 4.5–5 MPa m1/2 for use in extreme wear conditions. Thermal conductivities of up to 500 W/(m K) were obtained, render these materials interesting for heat sinks.

Cellular elasticity is frequently measured to investigate the biomechanical effects of drug treatment, diseases, and aging. In light of the cellular viscosity property exhibited by filament actin networks, this study investigates the viscoelasticity alterations of the human hepatocellular carcinoma (SMMC-7721) cell subjected to fullerenol treatment by means of creep tests realized by atomic force microscopy indentation. An SMMC-7721 cell was first modeled as a sphere and then as a flattened layer with finite thickness. Both Sneddon’s solutions and the Dimitriadis model have been modified to adapt to the viscoelastic situation, which are used to fit the same indentation depth–time curves obtained by creep tests. We find that the SMMC-7721 cell’s creep behavior is well described by the two modified models and the divergence of parameters determined by the two models is justified. By fullerenol treatment, the SMMC-7721 cell exhibits a significant decrease of elastic modulus and viscosity, which is presumably due to the disruption of actin filaments. This work represents a new attempt to understand the alternation of the viscoelastic properties of cancerous cells under the treatment of fullerenol, which has the significance of comprehensively elucidating the biomechanical effects of anticancer agents (such as fullerenol) on cancer cells.

The thermal expansion behavior of polymer carbon nanotube (CNT) nanocomposites was investigated, and a micromechanical model was proposed to explain the highly nonlinear dependence of the coefficient of thermal expansion of the nanocomposite with CNT content for the CNT/polyimide nanocomposite. The microscopic analysis of CNT/polyimide matrix showed homogeneous dispersion of bundles composed of CNTs. Therefore, the proposed model to predict the thermal expansion behavior of the nanocomposite considered a random, homogeneous distribution of CNT bundles with a hierarchical arrangement of helical CNTs within the polymeric matrix. The CNT bundle morphology influenced the thermal expansion response of the nanocomposite through (i) bundle volume fraction and (ii) degree of helicity, affecting thermo-mechanical properties of the bundle. The effective, homogenized, properties of CNT bundles were determined by the elasticity based solution of the layered cylinder model. Bundle effective properties were used in the micromechanical model implementing the homogenized strain rule of the mixture expression to predict the thermal expansion behavior of nanocomposite in a wide range of CNT volume contents. The proposed micromechanical analytical model was found to correlate closely with the experimental results for polyimide/CNT nanocomposite films as measured using a digital image correlation method.

Two novel porphyrins (5,10,15,20-tetra(3-(carboethoxymethyleneoxy)phenyl)porphyrin, H2TEPp and 5,10,15,20-tetra(3-(carboxymethyleneoxy)phenyl)porphyrin, H2TCPp) and their copper(II) porphyrins (CuTEPp, CuTCPp) were synthesized. With these porphyrins, four new porphyrin-sensitized TiO2 nanorod composites (H2TEPp/TiO2, H2TCPp/TiO2, CuTEPp/TiO2, and CuTCPp/TiO2) were prepared and characterized by methods of XRD, SEM, TEM, FT-IR, UV-vis DRS, nitrogen adsorption–desorption and fluorescence spectra. Besides, the photocatalytic activity and stability of the composites were assessed in the degradation of 4-nitrophenol (4-NP). The results indicate that the morphologies and structures of these composites are less influenced by the loaded porphyrins or copper porphyrins compared with the nanorods TiO2 (anatase). The porphyrin or copper porphyrin molecules are confirmed to bond on the surface of TiO2 through carboxyl group, which is beneficial to the electron transfer between porphyrin and TiO2. All composites exhibit enhanced photoactivities compared with the bare TiO2 nanorods. The possible reason is that the recombination of photoproduced electron–hole has been controlled effectively in these composites, which can be seen from their decreased fluorescence emission. The stability results of composites show that they still hold considerable photocatalytic activities after six cycling experiments.