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In practice, the capacitance from the electrochemical double layer formation on porous carbon‐based electrodes is still below preferred values, limiting their use in electrochemical capacitors. The current drive is to innovate ways that generate additional capacitance in the electrochemical double layer capacitive nature of carbon nanomaterials towards both a high specific energy density (Es) and power density (Ps). Herein we report the use of metal‐organic chemical vapor deposition (MOCVD) to coat multiwalled carbon nanotubes (MWCNTs) with anatase titanium dioxide (TiO2) to induce pseudocapacitive charge storage characteristics on a carbon‐based electrode. The study shows that MWCNTs were coated in bundles, and targeted TiO2 loadings were successfully attained, though the TiO2 agglomerates also increased with TiO2 wt.%. The 10 wt.% TiO2 TiO2‐MWCNT material displayed the best capacitive behavior with associated specific discharge capacitance (Cd), Es, and Ps values of 907 F kg−1, 55.56 Wh kg−1, and 2.78 W kg−1 at 0.1 A g−1, respectively, due to the synergistic effect of the two components of the composite. Additionally, the integral capacitance (Cs) of the 20 wt.% TiO2 material was enhanced more than 5000‐fold relative to that of the 5 wt.% TiO2 TiO2‐MWCNT composite at higher scan speeds of 100 and 200 mV s−1. Electrochemical measurements further demonstrated the possible positive tuning of capacitive characteristics (charge/discharge rates, Cd and Cs) with TiO2 wt.% control. The MOCVD synthesis method imparted the TiO2‐MWCNT composites with suitable traits that showed high potential in improving physicochemical processes favorable in electrical energy storage. [ABSTRACT FROM AUTHOR]

Colloidal metal chalcogenide quantum dots (QDs) have excellent quantum efficiency in light–matter interactions and good device stability. However, QDs have been brought to the forefront as viable building blocks in bottom‐up assembling semiconductor devices, the development of QD solar cell (QDSC) is still confronting considerable challenges compared to other QD technologies due to their low performance under natural sunlight, as a consequence of untapped potential from their quantized density‐of‐state and inorganic natures. This report is designed to address this long‐standing challenge by accessing the feasibility of using QDSC for indoor and concentration PV (CPV) applications. This work finds that above bandgap photon energy irradiation of QD solids can generate high densities of excitons via multi‐photon absorption (MPA), and these excitons are not limited to diffuse by Auger recombination up to 1.5 × 1019 cm−3 densities. Based on these findings, a 19.5% (2000 lux indoor light) and an 11.6% efficiency (1.5 Suns) have been facilely realized from ordinary QDSCs (9.55% under 1 Sun). To further illustrate the potential of the MPA in QDSCs, 21.29% efficiency polymer lens CPVs (4.08 Suns) and viable sensor networks powered by indoor QDSCs matrix have been demonstrated. [ABSTRACT FROM AUTHOR]

Soil water repellency, that is, the reduced ability of soils to absorb water, is thought to be caused by organic coatings with predominantly non‐polar properties on soil particle surfaces. Given the important role of particle surface polarity in determining soil water repellency, we explored the use of fluorescent probes as a method for the direct in‐situ determination of the distribution and polarity of organics on bulk soil surfaces, and of their molecular mobility. We used nile red and pyrene, which have both been used successfully as environmental probes in previous studies, but have not been applied before to bulk soils. The probes were either (a) co‐deposited with other organics known to induce water‐repellent behaviour with acid‐washed sand to produce 'model soils' or (b) adsorbed directly onto sandy soils that were naturally water repellent to different degrees, and studied using fluorescence microscopy and steady‐state and time‐resolved fluorescence. Reliable measurements could be made using pyrene as an in‐situ probe on both model and natural soils, and a viscosity/mobility probe on model soils, whereas nile red was found not to be a useful probe. On model soils, made using hexadecane (HEX), octadecane (OCT) or stearic acid (SA) on acid‐washed sand, pyrene excimer formation kinetics showed a decrease in environment mobility as the organic layer changes from a liquid through to a hard wax. Spectra from pyrene adsorbed to natural soils indicated varying environmental polarity and heterogeneity within the soil samples studied. Highlights: Exploration of in‐situ fluorescent probes to study polarity and viscosity of organics on soils.Fluorescent probes have never been used in situ on bulk soils before.Pyrene probe shows variation in mobility, polarity and heterogeneity of organics on soils.Pyrene is a useful in‐situ fluorescent probe of polarity and mobility of organics on soils. [ABSTRACT FROM AUTHOR]

Perovskite solar cells have attracted a great deal of attention thanks to their high efficiency, ease of manufacturing, and potential low cost. However, the stability of these devices is considered their main drawback and needs to be addressed. Mesoporous carbon perovskite solar cells (m‐CPSC), consisting of three mesoporous layers (TiO2/ZrO2/C) infiltrated with CH3NH3PbI3 (MAPI) perovskite, have presented excellent lifetimes of more than 10 000 h when the additive NH2(CH2)4CO2HI (5‐ aminovaleric acid iodide; 5‐AVAI) is used to modify the perovskite structure. Yet, the role of 5‐AVAI in enhancing the stability has yet to be determined. Here, superoxide‐mediated degradation of MAPI m‐CPSC with and without the 5‐AVAI additive is studied using the fluorescence probe dihydroethidium for superoxide detection. In situ X‐ray diffractometry shows that aminovaleric acid methylammonium lead iodide (AVA‐MAPI) perovskite infiltrated in mesoporous layers presents higher stability in an ambient environment under illumination, evidenced by a slower decrease of the MAPI/PbI2 peak ratio. Superoxide yield measurements demonstrate that AVA‐MAPI generates more superoxide than regular MAPI when deposited on glass but generates significantly less when infiltrated in mesoporous layers. It is believed that superoxide formation in m‐CPSC is dependent on a combination of competitive factors including oxygen diffusion, sample morphology, grain size, and defect concentration. [ABSTRACT FROM AUTHOR]