Plasmonic protein electricity generator.

Interest in acquiring green energy from sunlight is driving research into the incorporation of biological photosynthetic materials into biohybrid devices. A potential way to enhance solar energy conversion by photosynthetic proteins is to couple them to plasmonic nanomaterials to enhance absorption of incident radiation. In this work, a variety of plasmonic nanoparticles were used to boost the photocurrent output of a Protein Electricity Generator (PEG). Mixing gold nanoparticles (NPs) of five different architectures into the photoprotein/electrolyte contents of the cell was found to increase device performance, the most effective being ∼120 nm diameter star-shaped clusters that caused a ∼six-fold increase in photocurrent at the optimum dopant level. In addition, high-resolution electrohydrodynamic printing was used to create parallel line and square lattice patterns of silver nanoparticle ink on the tungsten rear electrode of the cells. Patterns with a 700 nm spacing between lines boosted photocurrents by up to three-fold and the effects of the gold and silver nanoparticles were additive, such that the ideal combination produced a ∼19-fold increase in photocurrent and device efficiency. We attribute the elevated performance to plasmonic enhancement of absorbance and scattering effects that increase the path length for photons in the device. Use of rear electrodes with silver nanoparticle lines and grids at 1100 nm spacing did not increase photocurrents, highlighting the importance of precision printing of nanostructures for the enhancement of device performance.

Liquid-Exfoliated 2D Materials for Optoelectronic Applications.

Two-dimensional (2D) materials have attracted tremendous research attention in recent days due to their extraordinary and unique properties upon exfoliation from the bulk form, which are useful for many applications such as electronics, optoelectronics, catalysis, etc. Liquid exfoliation method of 2D materials offers a facile and low-cost route to produce large quantities of mono- and few-layer 2D nanosheets in a commercially viable way. Optoelectronic devices such as photodetectors fabricated from percolating networks of liquid-exfoliated 2D materials offer advantages compared to conventional devices, including low cost, less complicated process, and higher flexibility, making them more suitable for the next generation wearable devices. This review summarizes the recent progress on metal-semiconductor-metal (MSM) photodetectors fabricated from percolating network of 2D nanosheets obtained from liquid exfoliation methods. In addition, hybrids and mixtures with other photosensitive materials, such as quantum dots, nanowires, nanorods, etc. are also discussed. First, the various methods of liquid exfoliation of 2D materials, size selection methods, and photodetection mechanisms that are responsible for light detection in networks of 2D nanosheets are briefly reviewed. At the end, some potential strategies to further improve the performance the devices are proposed.

Shadow enhanced self-charging power system for wave and solar energy harvesting from the ocean.

Hybrid energy-harvesting systems that capture both wave and solar energy from the oceans using triboelectric nanogenerators and photovoltaic cells are promising renewable energy solutions. However, ubiquitous shadows cast from moving objects in these systems are undesirable as they degrade the performance of the photovoltaic cells. Here we report a shadow-tribo-effect nanogenerator that hybrids tribo-effect and shadow-effect together to overcome this issue. Several fiber-supercapacitors are integrated with the shadow-tribo-effect nanogenerator to form a self-charging power system. To capture and store wave/solar energy from oceans, an energy ball based on the self-charging power system is demonstrated. By harnessing the shadow-effect, i.e. the shadow of the moving object in the energy ball, the charging time shortens to 253.3 s to charge the fiber-supercapacitors to the same voltage (0.3 V) as using pure tribo-effect. This cost-effective method to harvest and store the wave/solar energy from the oceans in this work is expected to inspire next-generation large-scale blue energy harvesting.

Ultrafast Exfoliation of 2D Materials by Solvent Activation and One-Step Fabrication of All-2D-Material Photodetectors by Electrohydrodynamic Printing.

Large-scale liquid exfoliation of two-dimensional materials such as molybdenum disulfide, tungsten disulfide, and graphene for the synthesis of printable inks is still inefficient due to many hours of exfoliation time needed to achieve a highly concentrated dispersion that is useful for printing. Here, we report that soaking the bulk 2D material powders in a variety of solvents (water, ethanol, isopropanol, acetone, methanol, dimethylformamide, N-methyl pyrrolidone, and hexane) briefly as short as 5 min "activates" them to be much more easily exfoliated afterward. The unsoaked powder yielded a negligible concentration of dispersed nanosheets (less than 0.01 mg/mL) even after long hours of sonication, while the powders soaked in water resulted in dispersed nanosheets of 1.21 mg/mL for MoS2 and 1.28 mg/mL for WS2 after 6 and 4 h of sonication, respectively, a more than 100 time increase. For graphene, soaking in methanol for 5 min prior to sonication for 6 h yielded an increase in the dispersed nanosheet concentration to 0.13 mg/mL, a more than 10 time increase in concentration. The enhanced exfoliation is originated not from the intercalated solvent molecules but from the slightly increased d-spacing of the bulk powders during soaking due to the different dielectric environments in the solvents, which assists in the exfoliation afterward. We further fabricated MoS2 and WS2 photodetectors with graphene as electrodes by one-step electrohydrodynamic (EHD) printing using highly concentrated inks (>2 mg/mL) obtained by ultrafast liquid exfoliation, which have light sensitivity down to 0.05 sun. We believe that this ultrafast exfoliation technique combined with the one-step device printing technique enables a big step toward the mass production of functional devices fabricated from solution-processed 2D material inks.

A Hybrid Artificial Photocatalysis System Splits Atmospheric Water for Simultaneous Dehumidification and Power Generation.

A new approach for artificial photocatalysis of electrical generation directly from atmospheric water is reported. A hybrid system comprising a hydrogel incorporated with Cu2 O and BaTiO3 nanoparticles is developed, wherein the Cu2 O is designed to expose two different crystal planes, namely (100) and (111). These planes exhibit different surface potentials and form a polarization electric field of 2.3 kV cm-1 that acts on a ferroelectric dipole. With the help of this electric field, the dipole is redirected for aiding in positive and negative polarizations with (100) and (111) planes, then boosting water reduction and oxidation kinetics separately at (100) and (111) planes. Additonally, zinc-/cobalt-based superhygroscopic hydrogels serve as a water-capturing "hand" to harness humidity from the ambient environment. The integrated hydrogel-Cu2 O@BaTiO3 hybrid is used to dehumidify air, which can split 36.5 mg of water by employing only 150 mg hydrogel and simultaneously generate a photocurrent of 224.3 µA cm-2 under 10 mW cm-2 illumination.