This report investigates the influence of surface chemistry (or wettability) on the evaporation performance of free-standing double-layered thin film on the surface of water. Such newly developed evaporation system is composed of top plasmonic light-to-heat conversion layer and bottom porous supporting layer. Under solar light illumination, the induced plasmonic heat will be localized within the film. By modulating the wettability of such evaporation system through the control of surface chemistry, the evaporation rates are differentiated between hydrophilized and hydrophobized anodic aluminum oxide membrane-based double layered thin films. Additionally, this work demonstrated that the evaporation rate mainly depends on the wettability of bottom supporting layer rather than that of top light-to-heat conversion layer. The findings in this study not only elucidate the role of surface chemistry of each layer of such double-layered evaporation system, but also provide additional design guidelines for such localized evaporation system in applications including desalination, distillation and power generation.

The plasmonic heating effect of noble nanoparticles has recently received tremendous attention for various important applications. Herein, we report the utilization of interfacial plasmonic heating-assisted evaporation for efficient and facile solar-thermal energy harvest. An airlaid paper-supported gold nanoparticle thin film was placed at the thermal energy conversion region within a sealed chamber to convert solar energy into thermal energy. The generated thermal energy instantly vaporizes the water underneath into hot vapors that quickly diffuse to the thermal energy release region of the chamber to condense into liquids and release the collected thermal energy. The condensed water automatically flows back to the thermal energy conversion region under the capillary force from the hydrophilic copper mesh. Such an approach simultaneously realizes efficient solar-to-thermal energy conversion and rapid transportation of converted thermal energy to target application terminals. Compared to conventional external photothermal conversion design, the solar-thermal harvesting device driven by the internal plasmonic heating effect has reduced the overall thermal resistance by more than 50% and has demonstrated more than 25% improvement of solar water heating efficiency.

This paper presents a new steam sterilization approach that uses a solar-driven evaporation system at the water/air interface. Compared to the conventional solar autoclave, this new steam sterilization approach via interfacial evaporation requires no complex system design to bear high steam pressure. In such a system, a reduced graphene oxide/polytetrafluoroethylene composite membrane floating at the water/air interface serves as a light-to-heat conversion medium to harvest and convert incident solar light into localized heat. Such localized heat raises the temperature of the membrane substantially and helps generate steam with a temperature higher than 120 °C. A sterilization device that takes advantage of the interfacial solar-driven evaporation system was built and its successful sterilization capability was demonstrated through both chemical and biological sterilization tests. The interfacial evaporation-based solar driven sterilization approach offers a potential low cost solution to meet the need for sterilization in undeveloped areas that lack electrical power but have ample solar radiation.

This paper explores a new propulsion mechanism that is based on the ejection of hot vapor jet to propel the motor at the liquid/air interface. For conventional photothermal motors, which mostly are driven by Marangoni effect, it is challenging to propel those motors at the surfaces of liquids with low surface tension due to the reduced Marangoni effect. With this new vapor-enabled propulsion mechanism, the motors can move rapidly at the liquid/air interface of liquids with a broad range of surface tensions. A design that can accumulate the hot vapor is further demonstrated to enhance both the propulsion force as well as the applicable range of liquids for such motors. This new propulsion mechanism will help open up new opportunities for the photothermal motors with desired motion controls at a wide range of liquid/air interfaces where hot vapor can be generated.

Articles you may be interested inEnhancement of thermal conductivity of silver nanofluid synthesized by a one-step method with the effect of polyvinylpyrrolidone on thermal behavior Appl. Phys. Lett. 102, 231907 (2013); 10.1063/1.4809998 Effect of particle size on the thermoluminescence properties of Ba 0.97 Ca 0.03 SO 4 : Cu AIP Conf. Proc. 1512, 446 (2013); 10.1063/1.4791103 Unusual metallic behavior in nanostructured cobalt ferrite at superparamagnetic regime J. Appl. Phys. 112, 063926 (2012); 10.1063/1.4754855Thermal conductivity of polyethylene glycol nanofluids containing carbon coated metal nanoparticles Nanofluids consist of nanoparticles dispersed in heat transfer carrier fluid and are typically used for enhancing thermal conductivity in devices and systems. This study investigated the synthesis of iron and copper nanoparticle-based thermal fluids prepared using a two-step process. Chemical precipitation was used for the synthesis of the powders, and ultrasonic irradiation was used to disperse the nanoparticles in the carrier fluid ͑ethylene glycol͒. The size distributions of the nanopowders in the carrier fluid were determined using dynamic light scattering resulting in average particle sizes of around 500 nm. The crystallite sizes of the powders were below 20 nm. Thus, both types of nanofluids are comparable with regard to crystallite size, particle size, and morphology resulting in a direct comparison of material properties and their effect on thermal conductivity of the nanofluids. A guarded hot parallel-plate method and dynamic tests were used to compare the thermal conductivities of the nanofluids. It was shown that thermal conductivity can be enhanced by up to 70% for copper nanofluids. It was also demonstrated that for a given particle concentration, copper nanofluids are superior in thermal conductivity compared to iron nanofluids.

This paper reports the highly efficient pyroelectric nanomaterial-based catalytic degradation of waste dye under rapid temperature oscillation, which was achieved by periodical solar irradiation on a porous pyroelectric membrane that was floating at the liquid/air interface. Such a membrane consists of the light-to-heat conversion carbon black film as the top layer and the porous poly(vinylidene difluoride) (PVDF) film embedded with pyroelectric barium titanate (BaTiO) nanoparticles (BTO NPs) as the bottom layer. By using an optical chopper, solar light can be modulated to periodically irradiate on the floating membrane. Because of the photothermal effect and low thermal conductivity of the PVDF polymer, the generated heat is localized at the surface of the membrane and substantially increases the surface temperature within a short period of time. When the solar light is blocked by the chopper, interfacial evaporation through the porous membrane along with convective air cooling and radiative cooling leads to heat dissipation, and then the temperature of the membrane is rapidly decreased. Such an efficient thermal cycle results in a substantial rate of temperature change of the membrane, which enhances its pyroelectric capability and subsequent pyro-catalysis. In contrast, the efficiency of pyro-catalysis through the dispersed BTO NP solution is about 4 times lower than that of the BTO composite membrane. With the large heat capacity of the aqueous solution and inevitable thermal loss because of bulk heating, the rate of temperature change of the BTO NP solution is much smaller than that of the BTO composite membrane and thus results in a relatively small pyro-catalytic capability. Furthermore, the reusability and transferability of this newly developed composite membrane make it amenable to practical use in treating contaminated water. The findings in our report not only offer a new design strategy for efficient solar-enabled pyro-catalysis but also pave a new way to rationally harvest solar-thermal energy in nature for various applications that involve pyroelectric materials.

Solar-driven interfacial evaporation, as one of the most effective ways to convert and utilize solar energy, has attracted lot of interest recently. Most of the previous research studies, however, mainly focused on nonpatterned solar absorbers by improving the structural and chemical characteristics of the solar absorbers used in the interfacial evaporation systems. In this work, we investigated the influence of patterned surface on the evaporation performance of solar absorbers. The patterned surfaces studied, which include black patterns and white patterns, were achieved by selectively printing carbon black on the air-laid paper. Such a design leads to the lateral temperature differences between adjacent patterns of the solar absorber under solar illumination. The temperature differences result in the lateral heat and mass transfer between those patterns, which can effectively accelerate solar-driven vapor generation. With similar patterns and same coverage of carbon black, the increase in the circumference of the surface patterns leads to the increase in the evaporation performance. Additionally, we found that the evaporation performance can be optimized through the design of surface patterns, which demonstrates the potential in reducing the usage of the light-absorbing materials in the solar absorber. The findings in this work not only expand the understanding of the interfacial evaporation systems but also offer additional guidelines in designing interfacial evaporation systems.

This paper presents a pyroelectric approach for the synthesis of metal−BaTiO 3 hybrid nanoparticles (NPs) and demonstrates the enhanced performance on the degradation of dye solution using such hybrid NPs. During the synthesis process, rapid temperature oscillation accelerated the electron generation at the surface of pyroelectric barium titanate (BTO) NPs that were dispersed in either aqueous or nonaqueous solutions. These generated electrons were used to reduce the metal salts on the surface of BTO NPs without the need for a reducing reagent. The Au− BTO hybrid NPs synthesized by such approach showed higher pyrocatalytic degradation efficiency for dye solution than the physically mixed solutions of Au NPs and BTO NPs. Compared to conventional processes, this pyrocatalytic approach without the need for additional reducing reagents not only offers an alternative strategy for the synthesis of metal−pyroelectric hybrid materials but also opens a new way to harvest thermal energy for efficient pyrocatalysis process.