RESUMEN
In this work, the dependence of effective Young's modulus on the thickness of suspended graphene was confirmed through a drop impingement method. Large area suspended graphene (LSG) layers with a diameter of up to 400 µm and a nanometer thickness were prepared through transferring chemical vapor deposition grown graphene from copper substrates. 4, 8, and 12-layer LSG samples were found to be crumpled yet defect-free. The mechanical properties of LSG were first studied by observing its interaction with impinging droplets from an ink-jet nozzle. First, the effective Young's modulus was calculated by fitting the instant deformation captured by high speed photography within microseconds. Next, droplets deposited on LSG caused deformation and generated wrinkles and the effective Young's modulus was calculated from the number of wrinkles. The above methods yielded effective Young's modulus values ranging from 0.3 to 3.4 TPa. The results from these methods all indicated that the effective Young's modulus increases with the decreasing thickness or size of suspended graphene layers. Moreover, the crumpled LSG yields higher effective Young's modulus than ideal flat graphene. These comprehensive results from complementary methodologies with precise LSG thickness control down to the nanometer scale provide good evidence to resolve the debate on the thickness dependence of mechanical strength for LSG.
RESUMEN
In this study, a new preparation method is developed to include thermochromic complex ions in polydimethylsiloxane (PDMS) as a stretchable composite. Ethylene glycol (EG) droplets down to the nanometer scale were dispersed using a reverse micelle method to form a stable suspension in PDMS precursor solution. After curing, the EG nanodroplets were well encapsulated in the cured PDMS elastomer. The EG/PDMS composite exhibited great stability after thermal heating at 100 °C for 2 hours. The deformable liquid droplets helped maintaining the composite structures under severe stretching conditions, and thus the stretched composite exhibited great transparency without any fractures or delamination. Ionic dyes, such as methylene blue and Congo red, can be added in the EG droplets to color the composite. Moreover, complex ions with thermochromic properties can also be used in the composite. Upon thermal heating, the reconfiguration of the complex ions in the liquid dispersed phase led to obvious color changes, and the color remained unchanged up to 50% tensile strain after more than 1000 stretch cycles.
RESUMEN
In this study, a biosensor, based on a glucose oxidase (GOx) immobilized, carbon-coated tin sulfide (SnS) assembled on a glass carbon electrode (GCE) was developed, and its direct electrochemistry was investigated. The carbon coated SnS (C-SnS) nanoparticle was prepared through a simple two-step process, using hydrothermal and chemical vapor deposition methods. The large reactive surface area and unique electrical potential of C-SnS could offer a favorable microenvironment for facilitating electron transfer between enzymes and the electrode surface. The structure and sensor ability of the proposed GOx/C-SnS electrode were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and cyclic voltammetry study (CV).