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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.

Summary Direct utilization of abundantly available solar energy is a promising way to create a sustainable society. Here, we report a ferroelectric-semiconductor (BaTiO3@BiVO4) hybrid that uses an effective strategy to enhance charge separation and transfer during water oxidation. The tetragonal BaTiO3 can induce an outward vector of built-in electric field after positive polarization, which aids in increasing the photovoltage and accelerating holes’ transfer to BiVO4’s surface. A super-hygroscopic metal hydrogel serves as an atmospheric humidity harvester for continuous water supply to the hybrid, where water oxidation takes place. As the hydrogel absorbs moisture from ambient humid air, it functions as a dehumidifying agent and carries water to the photoanode for power generation, being connected in series with a solar cell, further boosting the carrier’s mobility. This photoanode-hydrogel and solar-cell intelligent assembly can generate a photocurrent of 0.4 mA/cm2 with a relative humidity reduction of 12.0% under an illumination of 10 mW/cm2.

Human-machine interfaces in emerging smart-skin technologies tend to be focussed towards high-sensitivity tactile sensing primarily with visual/numerical feedback, and research on e-skin technologies for the visually impaired is sparse. Here we demonstrate a proof-of-concept six-pixel tactile sensor that converts touch stimuli based on Braille codes into an auditory output, and which could potentially be miniaturized as an ‘energy-autonomous on-skin e-Braille reader’ for the visually impaired. By applying the concepts of electric double layer capacitance and bio-photo capacitance, a self-powered sensor is constructed that generates electrical signals as large as 2 V by modulating a bio-electrochemical liquid bridge between electrodes of opposite wetting characteristics. The liquid bridge, composed of photosynthetic pigment-proteins with a redox electrolyte, both augments the sensory response and serves as a standalone solar-capacitor that can generate a photocurrent as high as 140 µA cm-2, and which displays a long discharge time of ~20 mins with just ~3 mins of photo charging.

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., Ubiquitous shadows cast from moving objects in hybrid energy-harvesting systems are undesirable as they degrade the performance of the photovoltaic cells. Here the authors report the shadow of the moving object in a hybrid energy-harvesting system shortens charging time to charge a self-charging power system.

Photosynthetic proteins carry out photochemical charge separation with a near-unity quantum efficiency and provide interesting materials for sustainable solar energy conversion in man-made photoelectrochemical devices. The three-dimensional architectures of natural photosynthesisers on both macroscopic and microscopic length scales contrast strikingly with the essentially two-dimensional architectures of commercial photovoltaic devices. In this work we fabricated flexible and semi-transparent bio-photoelectrochemical cells (BPEC) that showed excellent flexibility and durability in response to repeated mechanical deformation. A three-dimensional stack of five such BPECs connected in parallel produced a peak photocurrent of 2900 nA under simulated sunlight in the laboratory and 2400 nA when tested outdoors. Placement of the BPEC stack within either a regular solid reflective well or a Johnson solid reflective well further boosted these photocurrents, computational analysis indicating that the strongest boost that more than doubled output was the consequence of multiple reflections within the Johnson solid that increased the light intensity incident on the BPEC stack. These design features, inspired by natural structures for absorbing and reflecting sunlight, improved the relative performance of the BPECs under non-peak insolation, such that the photocurrent output under natural sunlight was relatively uniform between 10 a.m. and 5 p.m. We discuss how the flexibility, durability and partial transparency of the individual BPECs enable the fabrication of cell arrays with a range of three-dimensional architectures.

Tridentate, bis-phenolate N-heterocyclic carbenes (NHCs) are among the ligands giving the most selective and active group 4-based catalysts for the copolymerization of cyclohexene oxide (CHO) with CO2. In particular, ligands based on imidazolidin-2-ylidene (saturated NHC) moieties have given catalysts which exclusively form polycarbonate in moderate-to-high yields even under low CO2 pressure and at low copolymerization temperatures. Here, to evaluate the influence of the NHC moiety on the molecular structure of the catalyst and its performance in copolymerization, we extend this chemistry by synthesizing and characterizing titanium complexes bearing tridentate bis-phenolate imidazol-2-ylidene (unsaturated NHC) and benzimidazol-2-ylidene (benzannulated NHC) ligands. The electronic properties of the ligands and the nature of their bonds to titanium are studied using density functional theory (DFT) and natural bond orbital (NBO) analysis. The metal&ndash, NHC bond distances and bond strengths are governed by ligand-to-metal &sigma, and &pi, donation, whereas back-donation directly from the metal to the NHC ligand seems to be less important. The NHC &pi, acceptor orbitals are still involved in bonding, as they interact with THF and isopropoxide oxygen lone-pair donor orbitals. The new complexes are, when combined with [PPN]Cl co-catalyst, selective in polycarbonate formation. The highest activity, albeit lower than that of the previously reported Ti catalysts based on saturated NHC, was obtained with the benzannulated NHC-Ti catalyst. Attempts to synthesize unsaturated and benzannulated NHC analogues based on Hf invariably led, as in earlier work with Zr, to a mixture of products that include zwitterionic and homoleptic complexes. However, the benzannulated NHC-Hf complexes were obtained as the major products, allowing for isolation. Although these complexes selectively form polycarbonate, their catalytic performance is inferior to that of analogues based on saturated NHC.

Summary Dual attributes of UV-photo-responsive organic-ionic conductors are exploited in bio-photoelectrochemical cells based on photosynthetic RC-LH1 proteins from Rhodobacter sphaeroides. These UV enhancer molecules (UVEM) can generate small photocurrents in the absence of protein and are also effective electrolytes for photocurrent generation by RC-LH1 complexes in response to near-infrared excitation. Mixing RC-LH1 and UVEM components strongly enhanced UV photocurrents relative to those obtained with protein or UVEM alone, an effect that is attributed to energy transfer from the hetero-anthracene chromophore of the UVEM to the carotenoids of the RC-LH1 complex. RC-LH1/UVEM bio-photoelectrochemical cells were superior to conventional RC-LH1 cells in terms of UV external quantum efficiency, photo-response sensitivity, and photocurrent rise-decay times. These bio-photodetectors could detect weak UV radiation with intensities as low as 2 μW/cm2. This combination of photosynthetic proteins with dual-function electrolytes is the first attempt to construct fully functional bio-photoelectrochemical UV photodetector based on natural components.

The development of new technologies that use sunlight as an energy source is adding to pressure on finite natural resources and the challenges of recycling and disposal. Looking to nature for material assistance, we describe a proof-of-concept flexible and biodegradable photoelectrochemical cell based almost entirely on pigments, proteins, polysaccharides, and graphene platelets. In addition to being largely environmentally benign, such devices present opportunities for the recovery of valuable components such as, in the present case, the geologically scarce metal indium and the precious metal gold. Recovery is achieved through dissolution in ethanol followed by physical separation of the heavy element, leaving a residue made up from common elements that can be recycled through natural biodegradation. Potential applications for flexible, biomolecule-based photoelectrochemical cells are considered.

Oxo- and imido-vanadium(V) metal complexes supported by bis(phenolate)-functionalized N-heterocyclic carbene (NHC) ligands were synthesized and structurally identified. In the presence of [(Ph3P=)2N]Cl ([PPN]Cl), saturated NHC oxo-vanadium complexes showed activity in the coupling of CO2 and cyclohexene oxide (CHO) into cis-cyclohexene carbonate (cis-CHC). More importantly, the oxo-vanadium complex bearing the less electron-donating benzannulated NHC ligand was found to be more active in CHO conversion to poly(cyclohexene carbonate) (PCHC) in addition to the cis-CHC, highlighting the beneficial effect of the weak electron-donating ability of the latter vs. saturated NHC ligands within such vanadium catalysts. Evaluation of the saturated NHC imido-vanadium catalyst performance led to the same activity and selectivity as the analogous oxo-vanadium catalysts owing to its reactivity with CO2 via a [2+2] cycloaddition reaction forming an oxo-vanadium species. publishedVersion

Natural photosynthetic proteins can convert solar energy into electrical energy with close to 100% quantum efficiency, and there is increasing interest in their use for sustainable photoelectrochemical devices. The primary processes of photosynthesis remain operational and efficient down to extremely low temperatures, and natural photosystems exhibit a variety of self-healing mechanisms. Herein we demonstrate the use of an amphiphilic triblock copolymer, Pluronic F127, to fabricate a self-healing photosynthetic protein photoelectrochemical cell that operates optimally at sub-zero temperatures. A concentration of 30% (w/w) Pluronic F127 depressed the freezing point of an electrolyte comprising 50 mM ubiquinone-0 in aqueous buffer such that optimal device solar energy conversion was seen at -12 °C rather than at room temperature. Fabrication of the protein photoelectrochemical cells with flexible electrodes enabled the demonstration of self-healing of damage caused by repeated mechanical deformation. Multiple bending cycles caused a marked deterioration of the photocurrent response to around a third of initial levels due to damage to the gel phase of the electrolyte, but this could be restored to ~95% by simply cooling and rewarming the device. This self-recoverability of the electrolyte extended the operational life of the protein cell through a process that increased its photoelectrochemical output during the repair. Utility of the cells as components of a touch sensor operational across a wide temperature range, including freezing conditions, is demonstrated.

Introduction: Stress is an important factor of depression that causes the changes in various body systems. The forced swim test is a commonly used stressor test where rats are forced to swim in specially constructed tanks for a particular period where there is behavioral activation characterized by vigorous swimming and diving to search for alternate routes of escape. Animal health including human has been shown to be affected by the stressful events of life inducing situation which alters cognition, learning memory and emotional responses, causing mental disorders like depression and anxiety and stress in rats. Methods: The experiment was carried out with 12 healthy albino Wistar female rats weighing about 150-180gms. The animals were randomly divided into two groups of six animals each. Group – I (control), Group – II (Stressed Group). Group –II rats are placed in plastic tanks for 45minutes for15 days. Temperature of water was maintained at 20˚C. During stress phase, the animals will be trained for forced swim test, behavioral changes observed by open field apparatus for emotions, and eight arm maze for memory & leaning, elevated plus maze for anxiety. Results: Forced swim stress causes to a significant change (p