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Register a new userEnhanced solar photothermal effect of PANi fabrics with plasmonic nanostructures
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The photothermal energy conversion in hanging and floating polyaniline (PANi)-cotton fabrics is investigated using a model based on the heat diffusion equation. Perfect absorption and anti-reflection of wet hanging PANi-cotton fabrics cause quick transfer of total incident light into water confining nearly 100 $%$ of the sunlight. As a result, a hanging membrane is found to have more attractive properties than a floating above water fabric. We find, however, that the photothermal properties of a floating PANi-cotton membrane can greatly be enhanced by dispersing TiN nanoparticles in the water below the fabric. The calculated temperature gradients for TiN nanoparticle solutions show that the absorbed energy grows with increasing the nanoparticle density and that the photothermal process occurs mostly near the surface. The collective heating effects depend on the size and density of nanoparticles, which can further be used to modulate the photothermal process.
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We propose a new approach to understand the time-dependent temperature increasing process of gold-silica core-shell nanoparticles injected into chicken tissues under near-infrared laser irradiation. Gold nanoshells strongly absorb near-infrared radiations and efficiently transform absorbed energy into heat. Temperature rise given by experiments and numerical calculations based on bioheat transfer are in good agreement. Our work improves the analysis of a recent study [Richardson et al., Nano Lett. 9, 1139 (2009)] by including effects of the medium perfusion on temperature increase. The theoretical analysis can also be used to estimate the distribution of nanoparticles in experimental samples and provide a relative accuracy prediction for the temperature profile of new systems. This methodology would provide a novel and reliable tool for speeding up photothermal investigations and designing state-of-the-art photothermal devices.
We theoretically investigate equilibrium behaviors and photothermal effects of a flexible plasmonic metamaterial composed of aramid nanofibers and gold nanoparticles. The fiber matrix is considered as an external field to reconfigure a nanoparticle assembly. We find that the heating process tunes particle-particle and fiber-particle interactions, which alter adsorption of nanoparticles on fiber surfaces or clustering in pore spaces. Thus, it is possible to control the nanoparticle self-assembly by laser illumination. Gold nanoparticles strongly absorb radiations and efficiently dissipate absorbed energy into heat. By solving the heat transfer equation associated with an effective medium approximation, we calculate the spatial temperature rise. Remarkably, our theoretical results quantitatively agree with prior experiments. This indicates that we can ignore plasmonic coupling effects induced by particle clustering. Effects of the laser spot size and intensity on the photothermal heating are also discussed.
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Plasmons in graphene nanostructures show great promise for mid-infrared applications ranging from a few to tens of microns. However, mid-infrared plasmonic resonances in graphene nanostructures are usually weak and narrow-banded, limiting their potential in light manipulation and detection. Here we investigate the coupling among graphene plasmonic nanostructures and further show that by engineering the coupling, enhancement of light-graphene interaction strength and broadening of spectral width can be achieved simultaneously. Leveraging the concept of coupling, we demonstrate a hybrid 2-layer graphene nanoribbon array which shows 5 to 7% extinction within the entire 8 to 14 {mu}m (~700 to 1250 cm-1) wavelength range, covering one of the important atmosphere infrared transmission windows. Such coupled hybrid graphene plasmonic nanostructures may find applications in infrared sensing and free-space communications.
Periodic arrays of air nanoholes in thin metal films that support surface plasmon resonances can provide an alternative approach for boosting the light-matter interactions at the nanoscale. Indeed, nanohole arrays have garnered great interest in recent years for their use in biosensing, light emission enhancement and spectroscopy. However, the large-scale use of nanohole arrays in emerging technology requires new low-cost fabrication techniques. Here, we demonstrate a simple technique to fabricate nanohole arrays and examine their photonic applications. In contrast to the complicated and most commonly used electron beam lithography technique, hexagonal arrays of nanoholes are fabricated by using a simple combination of shadowing nanosphere lithography technique and electron beam deposition. These arrays are shown to offer enhancements in the lasing emission of an organic dye liquid gain medium with a quality factor above 150. Additionally, a 7-fold increase in Purcell factor is observed for CdSe quantum dot-integrated nanohole arrays.
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