Abstract
The right balance between photo‐absorption and electronic‐ionic conductivity is needed for photo‐rechargeable bifunctional devices for off‐grid energy applications. Recently halide ...perovskites have been utilized for photo‐rechargeable supercapacitors, but the mechanism of photo‐capacitance enhancement is not known. Herein, we have fabricated mixed halide perovskites‐based photo‐rechargeable supercapacitors in two ways and examined the energy harvesting and storage capabilities of these devices. The porous electrode prepared from the mixed halide perovskites (CH
3
NH
3
PbBr
2
I) shows photo‐capacitance enhancement up to 15 F/g, while the electrode prepared from the blend of CH
3
NH
3
PbBr
3
and CH
3
NH
3
PbI
3
(2 : 1 by molar ratio) shows the photo‐capacitance diminution up to 12 F/g. Despite higher specific capacitance (~38 F/g in dark) in blend perovskites due to increased ion diffusion, the photo‐generated charge trapping at nanoscale phase segregation is responsible for the diminution in photo‐capacitance of these bifunctional devices, while a uniform mixing of halide ions in mixed halide perovskites nanocrystals leads to increased photo‐capacitance.
A remarkable PL enhancement by 12 fold is achieved using pressure to modulate the structure of a recently developed 2D perovskite (HA)2(GA)Pb2I7 (HA=n‐hexylammonium, GA=guanidinium). This structure ...features a previously unattainable, extremely large cage. In situ structural, spectroscopic, and theoretical analyses reveal that lattice compression under a mild pressure within 1.6 GPa considerably suppresses the carrier trapping, leading to significantly enhanced emission. Further pressurization induces a non‐luminescent amorphous yellow phase, which is retained and exhibits a continuously increasing band gap during decompression. When the pressure is released to 1.5 GPa, emission can be triggered by above‐band gap laser irradiation, accompanied by a color change from yellow to orange. The obtained orange phase could be retained at ambient conditions and exhibits two‐fold higher PL emission compared with the pristine (HA)2(GA)Pb2I7.
A remarkably enhanced emission (by 12‐fold) is achieved using pressure to modulate the structure of a highly distorted 2D halide perovskite (HA)2(GA)Pb2I7. In situ structural, spectroscopic, and theoretical analyses reveal that lattice compression under a mild pressure within 1.6 GPa considerably suppresses the carrier trapping, leading to the significantly improved performance.
Halide‐perovskite‐based mechanical energy harvesters display excellent electrical output due to their unique ferroelectricity and dielectricity. However, their high toxicity and moisture sensitivity ...impede their practical applications. Herein, a stretchable, breathable, and stable nanofiber composite (LPPS‐NFC) is fabricated through electrospinning of lead‐free perovskite/poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) and styrene–ethylene–butylene–styrene (SEBS). The Cs3Bi2Br9 perovskites serve as efficient electron acceptors and local nucleating agents for the crystallization of polymer chains, thereby enhancing the electron‐trapping capacity and polar crystalline phase in LPPS‐NFC. The excellent energy level matching between Cs3Bi2Br9 and PVDF‐HFP boosts the electron transfer efficiency and reduces the charge loss, thereby promoting the electron‐trapping process. Consequently, this LPPS‐NFC‐based energy harvester displays an excellent electrical output (400 V, 1.63 µA cm−2, and 2.34 W m−2), setting a record of the output voltage among halide‐perovskite‐based nanogenerators. The LPPS‐NFC also exhibits excellent stretchability, waterproofness, and breathability, enabling the fabrication of robust wearable devices that convert mechanical energy from different biomechanical motions into electrical power to drive common electronic devices. The LPPS‐NFC‐based energy harvesters also endure extreme mechanical deformations (washing, folding, and crumpling) without performance degradation, and maintain stable electrical output up to 5 months, demonstrating their promising potential for use as smart textiles and wearable power sources.
A stretchable, breathable, and stable nanofiber composite (LPPS‐NFC) through electrospinning of lead‐free perovskite/poly(vinylidene fluoride‐co‐hexafluoropropylene (PVDF‐HFP) and styrene–ethylene–butylene–styrene (SEBS) is reported. The Cs3Bi2Br9 perovskites exhibit great charge trapping capacity and energy level matching with PVDF‐HFP. As a result, the LPPS‐NFC‐based energy harvester displays excellent electrical output (400 V, 2.34 W m−2), setting a record of the output voltage among halide‐perovskite‐based nanogenerators.
Microscopically controlled neutral atoms in optical tweezers and lattices have led to exciting advances in the study of quantum information and quantum many-body systems. The light shifts of atomic ...levels from the trapping potential in these systems can result in detrimental effects such as fluctuating dipole force heating, inhomogeneous detunings, and inhibition of laser cooling, which limits the atomic species that can be manipulated. In particular, these light shifts can be large enough to prevent loading into optical tweezers directly from a magneto-optical trap. We implement a general solution to these limitations by loading, as well as cooling and imaging the atoms with temporally alternating beams, and present an analysis of the role of heating and required cooling for single atom tweezer loading. Because this technique does not depend on any specific spectral properties, it should enable the optical tweezer platform to be extended to nearly any atomic or molecular species that can be laser cooled and optically trapped.
A new class of lanthanide‐doped upconversion nanoparticles are presented that are without Yb3+ or Nd3+ sensitizers in the host lattice. In erbium‐enriched core–shell NaErF4:Tm (0.5 mol %)@NaYF4 ...nanoparticles, a high degree of energy migration between Er3+ ions occurs to suppress the effect of concentration quenching upon surface coating. Unlike the conventional Yb3+‐Er3+ system, the Er3+ ion can serve as both the sensitizer and activator to enable an effective upconversion process. Importantly, an appropriate doping of Tm3+ has been demonstrated to further enhance upconversion luminescence through energy trapping. This endows the resultant nanoparticles with bright red (about 700‐fold enhancement) and near‐infrared luminescence that is achievable under multiple excitation wavelengths. This is a fundamental new pathway to mitigate the concentration quenching effect, thus offering a convenient method for red‐emitting upconversion nanoprobes for biological applications.
Contain your excitement: Core–shell design strategies are usually unable to prevent luminescence quenching caused by energy losses at lattice defects residing inside a nanocrystal. Through Tm3+‐mediated transient energy trapping, Er3+‐sensitized nanocrystals (NaErF4:Tm@NaYF4) displaying highly efficient upconversion emission are presented. These nanomaterials are capable of generating red and NIR emissions under multiple excitation wavelengths.
•Numerical study of dissolution and local capillary trapping in heterogeneous reservoir.•We have simulated ScCO2 spread and solutal fingering, and calculated plume moments.•Plume moments show ...restricted lateral ScCO2 spread for higher capillary heterogeneity.•Tortious diffusive boundary layer causes faster finger growth for permeability heterogeneity.•Patchy CO2 saturation is negatively correlated to heterogeneous capillary entry pressure.
Deep CO2 storage reservoirs show a wide range of heterogeneous structures across different scales. Here, we show how high-resolution heterogeneity in both permeability and capillary entry pressure control dissolution and local capillary trapping of supercritical CO2 (ScCO2). Prior works mainly considered homogeneous reservoirs or simplified heterogeneity with horizontal and fixed capillary transition zones. Most of those studies ignored simultaneous free-phase ScCO2 spreading and solutal fingering. To advance understanding of heterogeneity effects, we have performed two-dimensional numerical simulations for ScCO2 injection into the middle of a storage reservoir. We have computed metrics including the spatial plume moments to compare the dissolution trapping and spreading of ScCO2 during the injection and post-injection period for different variances and correlation lengths of log-normal permeability and capillary entry pressure fields. The results show that the second-order spatial moment of the ScCO2 saturation field in the horizontal direction decreases by 10% as the permeability variance increases from 0.1 to 3.0. But it decreases by 50% as the capillary entry pressure variance becomes 1.1. For higher capillary entry pressure variance, the ratio of dissolved CO2 mass to free-phase ScCO2 mass decreases, showing higher local capillary trapping. The vertical distance between the centers of mass of the ScCO2 and dissolved CO2 plumes (representing the downward flow of dissolved CO2 through solutal fingering) is greater for heterogeneous reservoirs.
Display omitted
► Strong water contact angle increase with pressure increase. ► Strong water contact angle decrease with increasing temperature. ► Minor influence of salinity on the water contact ...angle. ► Brine–CO2 interfacial tension γ computed with high precision with molecular dynamics for subcritical CO2 pressures.
In the context of carbon geo-sequestration projects, brine–CO2 interfacial tension γ and brine–CO2–rock surface water contact angles θ directly impact structural and residual trapping capacities. While γ is fairly well understood there is still large uncertainty associated with θ. We present here an investigation of γ and θ using a molecular approach based on molecular dynamics computer simulations. We consider a system consisting of CO2/water/NaCl and an α-quartz surface, covering a brine salinity range between 0 and 4molal. The simulation models accurately reproduce the dependence of γ on pressure below the CO2 saturation pressure at 300K, and over predict γ by ∼20% at higher pressures. In addition, in agreement with experimental observations, the simulations predict that γ increases slightly with temperature or salinity. We also demonstrate that for non-hydroxylated quartz surfaces, θ strongly increases with pressure at subcritical and supercritical conditions. An increase in temperature significantly reduces the contact angle, especially at low-intermediate pressures (1–10MPa), this effect is mitigated at higher pressures, 20MPa. We also found that θ only weakly depends on salinity for the systems investigated in this work.
Optical tweezers are a highly versatile tool for exploration of the mesoscopic world, permitting non-contact manipulation of nanoscale objects. However, direct illumination with intense lasers ...restricts their use with live biological specimens, and limits the types of materials that can be trapped. Here we demonstrate an indirect optical trapping platform which circumvents these limitations by using hydrodynamic forces to exert nanoscale-precision control over aqueous particles, without directly illuminating them. Our concept is based on optically actuated micro-robotics: closed-loop control enables highly localised flow-fields to be sculpted by precisely piloting the motion of optically-trapped micro-rotors. We demonstrate 2D trapping of absorbing particles which cannot be directly optically trapped, stabilise the position and orientation of yeast cells, and demonstrate independent control over multiple objects simultaneously. Our work expands the capabilities of optical tweezers platforms, and represents a new paradigm for manipulation of aqueous mesoscopic systems.
The radical intermediates formed upon UVA irradiation of titanium dioxide suspensions in aqueous and non-aqueous environments were investigated applying the EPR spin trapping technique. The results ...showed that the generation of reactive species and their consecutive reactions are influenced by the solvent properties (e.g., polarity, solubility of molecular oxygen, rate constant for the reaction of hydroxyl radicals with the solvent). The formation of hydroxyl radicals, evidenced as the corresponding spin-adducts, dominated in the irradiated TiO2 aqueous suspensions. The addition of 17O-enriched water caused changes in the EPR spectra reflecting the interaction of an unpaired electron with the 17O nucleus. The photoexcitation of TiO2 in non-aqueous solvents (dimethylsulfoxide, acetonitrile, methanol and ethanol) in the presence of 5,5-dimethyl-1-pyrroline N-oxide spin trap displayed a stabilization of the superoxide radical anions generated via electron transfer reaction to molecular oxygen, and various oxygen- and carbon-centered radicals from the solvents were generated. The character and origin of the carbon-centered spin-adducts was confirmed using nitroso spin trapping agents.
PDF
