Broad Light Research Articles

The use of LEDs as a light source for fluorescence pressure measurements

ABSTRACT We discuss the use of commercial high power light emitting diodes (LEDs) as a light source for fluorescence pressure measurements. The relatively broad light emitting spectra of single color LEDs (in comparison with lasers) do not prevent producing narrow fluorescence lines at least for two widely used pressure indicator materials, namely ruby () and strontium tetraborate (). Strongest responses of both pressure gauges were detected for the green color LEDs with the average wavelength . LEDs might be easily implemented for producing fiber-coupled, as well as the parallel light sources. LEDs were found to be efficient to replace laser sources in piston-cylinder cell and diamond anvil cell fluorescence pressure measurement setups.

Plasmonic enhanced branched Ag sensitized Cu2O–CuO/TiO2 heterojunction with unprecedented photocatalytic degradation under visible light

A novel plasmonic Ag assisted Cu2O–CuO/TiO2 heterojunction photocatalyst was prepared using a facile sol-gel technique, and its MB degradation efficiency was explored. The physicochemical, morphostructural, and spectroscopic analyses using XRD, UV–vis-DRS, SEM, TEM, Raman, ESR, PL and XPS showed the formation of Ag@Cu2O–CuO/TiO2 hybrid photocatalyst, exhibiting surface plasmon resonance (SPR) and interfacial ternary heterojunctions. The SPR exhibited by the bulbous branched Ag nanostructures resulted in broad visible light absorption that extended into the near-infrared region. This plasmonic-heterojunction hybrid photocatalyst has shown excellent photocatalytic degradation, far surpassing the performance of its pristine counterparts under visible light illumination. The improved photocatalytic degradation of MB is attributable to the synergistic impact of reduced electron-hole pair recombination owing to Cu2O–CuO/TiO2 ternary junction, broad visible light absorption and near-field enhancement through the surface plasmon resonance effect. The current study demonstrates an integrated plasmonic-heterojunction photocatalytic system that offers a promising avenue for enhancing photocatalytic performance in dye-contaminated water treatment.

Far-Red Light Mediated Carbohydrate Concentration Changes in Leaves of Sweet Basil, a Stachyose Translocating Plant.

Photosynthetic active radiation (PAR) refers to photons between 400 and 700 nm. These photons drive photosynthesis, providing carbohydrates for plant metabolism and development. Far-red radiation (FR, 701-750 nm) is excluded in this definition because no FR is absorbed by the plant photosynthetic pigments. However, including FR in the light spectrum provides substantial benefits for biomass production and resource-use efficiency. We investigated the effects of continuous FR addition and end-of-day additional FR to a broad white light spectrum (BW) on carbohydrate concentrations in the top and bottom leaves of sweet basil (Ocimum basilicum L.), a species that produces the raffinose family oligosaccharides raffinose and stachyose and preferentially uses the latter as transport sugar. Glucose, fructose, sucrose, raffinose, and starch concentrations increased significantly in top and bottom leaves with the addition of FR light. The increased carbohydrate pools under FR light treatments are associated with more efficient stachyose production and potentially improved phloem loading through increased sucrose homeostasis in intermediary cells. The combination of a high biomass yield, increased resource-use efficiency, and increased carbohydrate concentration in leaves in response to the addition of FR light offers opportunities for commercial plant production in controlled growth environments.

The efficient photothermal performance of organic polymeric material poly3-hexylthiophene for solar driven water evaporation and thermoelectric power generation

Photothermal materials for solar evaporators need to have broad light absorption ability and be able to convert into heat efficiently. At present, organic photothermal materials mainly have the problems of narrow absorption spectrum range and low photothermal conversion efficiency. In recent years, the development of photovoltaic materials has attracted the attention of researchers. However, the application of photovoltaic materials to the field of solar driven water evaporation is still rare. Poly(3-hexylthiophene), P3HT, is a typical p-type conjugated polymer that can achieve high power conversion efficiency. P3HT powder has a solar-thermal conversion efficiency of 11.26%. Its absorption range at 300–900 nm provides effective utilization of sunlight and has the potential as an excellent photothermal conversion material. We loaded P3HT into non-woven fabric to obtain an integrated device for simultaneous water evaporation and thermoelectric power generation, with evaporation rate of 1.04 kg m−2 h−1 and output voltage of 58 mV under 1 kW m−2 simulated solar irradiation. This study enriches the application of traditional photovoltaic materials in the field of solar-heat technique and provides guidance in the construction of solar evaporation devices for water-electricity co-generation.

Gradient Alloyed Quantum Dots for Photocatalytic Lignin Valorization via Proton Coupled Electron Transfer

In the field of photocatalytic lignin valorization, simultaneously fulfilling the requirements of broad light harvesting and strong redox ability has been a key challenge for single binary quantum dot (QD) photocatalyst systems. In order to address the problem, gradient alloyed QDs with funnel-shaped energy structures have been developed. The gradient energy level increases the photon absorption range, while the periphery energy bands at the funnel edge are sufficiently wide to preserve effective redox capacity. In this work, the gradient alloyed QD photocatalyst along with proton donors have been employed in enhancing the efficiency and selectivity of β-O-4 bond cleavage in lignin, realizing yields of target aromatic products phenol and acetophenone to increase up to 70% and 65%, respectively. The mechanism of conversion from the ketone intermediate to target products and how to choose suitable proton donors have been systematically investigated. We propose a proton-coupled electron transfer (PCET) photocatalytic strategy through producing a Cα radical from ketone with the help of acid possessing appropriate bond dissociation free energy (BDFE) and strong electronic transmission facilitating ability. The knowledge acquired in this work is useful for designing photocatalysts and proton donors that can effectively cleave bonds in lignin via the PCET mechanism.

Selective oxidation of amines powered with green light and oxygen over an anthraquinone covalent organic framework

The exploration of emerging photocatalysts like covalent organic frameworks (COFs) is an essential but challenging endeavor to find sustainable solutions for selective organic transformations. Anthraquinones are envisaged to construct COFs for visible light photocatalysis because their derivatives are employed industrially as oxidation catalysts or organic dyes. Herein, an anthraquinone COF, TpAQ-COF, is successfully constructed with 1,3,5-triformylphloroglucinol (Tp) and 2,6-diaminoanthraquinone (AQ). Then, the selective oxidation of amines over TpAQ-COF is implemented. Amines can be effectively converted into corresponding imines over TpAQ-COF powered with green light and oxygen, during which superoxide radical anion is discerned as the pivotal reactive oxygen species. This work suggests that COFs could inherit the advantages of molecular building blocks for selective reactions powered with broad visible light.

Oxygen vacancy-rich MoO 3 nanorods as photocatalysts for photo-assisted Li–O 2 batteries

Photo-assisted lithium–oxygen (Li–O₂) batteries have been developed as a new system to reduce a large overpotential in the Li–O₂ batteries. However, constructing an optimized photocatalyst is still a challenge to achieve broad light absorption and a low recombined rate of photoexcited electrons and holes. Herein, oxygen vacancy-rich molybdenum trioxide (MoO_3−<i>x</i>) nanorods are employed as photocatalysts to accelerate kinetics of cathode reactions in the photo-assisted Li–O₂ batteries. Oxygen vacancies on the MoO_3−<i>x</i> nanorods can not only increase light-harvesting capability but also improve electrochemical activity for the cathode reactions. Under illumination, the photoexcited electrons and holes are effectively separated on the MoO_3−<i>x</i> nanorods. During discharging, activated O₂ is reduced to Li₂O₂ by the photoexcited electrons from the MoO_3−<i>x</i> nanorods. The photoexcited holes can promote the decomposition of Li₂O₂ during subsequent charging. Accordingly, the photo-assisted Li–O₂ batteries with the MoO_3−<i>x</i> nanorods deliver an ultralow overpotential of 0.22 V, considerable rate capability, and good reversibility. We think that this work could give a reference for the exploitation and application of the photocatalysts in the photo-assisted Li–O₂ batteries.

Solvent engineering for triple cationic ITO-based mesoscopic tin perovskite solar cells

Besides negligible toxicity, tin-based perovskite solar cells (TPSCs) hold bright prospects in light of broad light harvesting beyond ∼850 nm rendering theoretical efficiencies higher than lead-based counterparts. However, tin perovskites which are as thin as ∼200 nm (cf., ∼500 nm or beyond for lead analogs) and populate tin defects (i.e., Sn4+ defects) especially on a top surface do not suffice to absorb all the incoming light and to convert it into electricity. Herein, we explore triple mesoscopic TPSCs and develop suitable tin perovskites via cation and solvent engineering. The predetermined body frame of TiO2 (ETM) / Al2O3 (insulator) / ITO (HTM and electrode) mesoporous scaffolds enables thickness control of tin perovskites with ease over micrometers (∼2 µm herein), where ETM stands for the electron transport material and HTM stands for the hole transport material. In mesoscopic TPSCs, ITO is partly buried in tin perovskites so that the Sn4+ defects-enriched surface is least influential to charge transfer. By leveraging a Cs cation and a N,N′-dimethylpropyleneurea solvent, demanding quality of tin perovskites for efficient conversion of light-to-electricity is satisfied such as relaxed and passivated crystals and Sn4+-lean defects. The resulting perovskites are well-suited in performance and stability to the mesoscopic TPSCs. Importantly, they are highly reproducible and attain high quantum efficiency of >90% over a broad range of light absorption from 400 to 700 nm. This remarkable quantum efficiency translates to photocurrent higher than >27 mA cm−2 (cf., theoretical limit: ∼31 mA cm−2). We herein enlighten the future of TPSCs by proposing a route for maximal light harvesting and its conversion.

Ab Initio Site‐Selective Occupancy and Luminescence Enhancement in Broadband NIR Emitting Phosphor Mg7Ga2GeO12:Cr3+

AbstractCr3+ activated near‐infrared (NIR) phosphors are getting unprecedented attention to fabricate the broad band NIR light emitting diodes (NIR‐LEDs) for nondestructive detection, bio‐imaging, and night vision. However, it remains a major challenge to obtain ultrabroadband NIR emitting phosphor with excellent quantum yield (QY). Here, a broadband NIR emitting phosphor Mg7Ga2GeO12:Cr3+ (MGGO: Cr3+) ranging from 600 to 1300 nm with an outstanding QY (93%) and large full width of half maximum (FWHM = 226 nm) is developed, in which the site occupancy tendency of Cr3+ in MGGO host is discussed in detail through combining the structure optimization and the first‐principles theory calculation with luminescent properties at low temperature. After that, the emission intensity of MGGO:Cr3+ is improved through partial substitution of Mg2+ by alkaline‐earth ions Ca2+, Sr2+, or Ba2+, and the luminescence enhancement mechanism is also investigated. Furthermore, the NIR pc‐LED device is fabricated by combining 450 nm blue LED chip with the brightest phosphor MGGO:Cr3+/Ba2+, and its potential applications are evaluated in the field of nondestructive detection, night vision, and bio‐imaging.

Exposure to cyan or red light inhibits the axial growth of zebrafish eyes

Myopia, or nearsightedness, is the most common type of refractive error and is characterized by a mismatch between the optical power and ocular axial length. Light, and more specifically the spectral composition of light, has been known to influence myopic axial growth. In this pilot study, we exposed zebrafish to illuminations that vary in spectral composition and screened for changes in axial length. The illumination spectra included narrow band ultra-violet A (UVA) (peak wavelength 369 nm), violet (425 nm), cyan (483 nm), green/yellow (557 nm), and red (633 nm) light, as well as broad band white light (2700 K and 6500 K), dim white light and broad spectrum (day) light. We found that rearing zebrafish in cyan or red light leads to a reduction of the ocular axial length. The results of this pilot study may contribute to new perspectives on the role of light and lighting as an intervention strategy for myopia control.

Niche Applications of MXene Materials in Photothermal Catalysis

MXene materials have found emerging applications as catalysts for chemical reactions due to their intriguing physical and chemical applications. In particular, their broad light response and strong photothermal conversion capabilities are likely to render MXenes promising candidates for photothermal catalysis, which is drawing increasing attention in both academic research and industrial applications. MXenes are likely to satisfy all three criteria of a desirable photothermal catalyst: strong light absorption, effective heat management, and versatile surface reactivity. However, their specific functionalities are largely dependent on their structure and composition, which makes understandings of the structure–function relationship of crucial significance. In this review, we mainly focus on the recent progress of MXene–based photothermal catalysts, emphasizing the functionalities and potential applications of MXene materials in fields of photothermal catalysis, and provide insights on design principles of highly efficient MXene–based photothermal catalysts from the atomic scale. This review provides a relatively thorough understanding of MXene–based materials for photothermal catalysis, as well as an in–depth investigation of emerging high-prospect applications in photothermal catalysis.

Rapid Synthesis of Oxygen-Deficient MoO3–x-rGO Composites for Synergistic Photothermal Seawater Desalination and Photocatalytic Sterilization

The development of efficient photothermal desalination devices is of great significance in solving the problem of freshwater shortage. The design and preparation of efficient photothermal materials with a broad light absorption range have been extensively studied. However, the performance of photothermal catalysts for synergistic purification of complex seawater is still facing significant challenges. Therefore, we report the rapid preparation of MoO3–x-rGO composites with synergistic photothermal and photocatalytic performance by the solid-phase microwave thermal shock method. The superhot spots created on the surface of microwave-reduced rGO induce the formation of MoO3–x with oxygen vacancies. Due to the localized surface plasmon resonance (LSPR) effect, the near-infrared photothermal and photocatalytic properties of MoO3–x-rGO catalysts are greatly improved. When the optimal composite catalyst (GMW-3) is illuminated by one sunlight, the seawater evaporation rate and photothermal conversion efficiency can reach 1.58 kg m–2 h–1 and 87.2%, respectively. Meanwhile, the GMW-3 composite evaporator shows excellent antibacterial performance under the synergistic effect of photothermal and photocatalysis during the evaporation process. These findings expand a new insight and platform to design efficient catalysts for large-scale seawater desalination and purification.

Porous and Water Stable 2D Hybrid Metal Halide with Broad Light Emission and Selective H2 O Vapor Sorption.

In this work we report a strategy for generating porosity in hybrid metal halide materials using molecular cages that serve as both structure-directing agents and counter-cations. Reaction of the [2.2.2] cryptand (DHS) linker with PbII in acidic media gave rise to the first porous and water-stable 2D metal halide semiconductor (DHS)2 Pb5 Br14 . The corresponding material is stable in water for a year, while gas and vapor-sorption studies revealed that it can selectively and reversibly adsorb H2 O and D2 O at room temperature (RT). Solid-state NMR measurements and DFT calculations verified the incorporation of H2 O and D2 O in the organic linker cavities and shed light on their molecular configuration. In addition to porosity, the material exhibits broad light emission centered at 617 nm with a full width at half-maximum (FWHM) of 284 nm (0.96 eV). The recorded water stability is unparalleled for hybrid metal halide and perovskite materials, while the generation of porosity opens new pathways towards unexplored applications (e.g. solid-state batteries) for this class of hybrid semiconductors.

Porous and Water Stable 2D Hybrid Metal Halide with Broad Light Emission and Selective H2O Vapor Sorption

AbstractIn this work we report a strategy for generating porosity in hybrid metal halide materials using molecular cages that serve as both structure‐directing agents and counter‐cations. Reaction of the [2.2.2] cryptand (DHS) linker with PbII in acidic media gave rise to the first porous and water‐stable 2D metal halide semiconductor (DHS)2Pb5Br14. The corresponding material is stable in water for a year, while gas and vapor‐sorption studies revealed that it can selectively and reversibly adsorb H2O and D2O at room temperature (RT). Solid‐state NMR measurements and DFT calculations verified the incorporation of H2O and D2O in the organic linker cavities and shed light on their molecular configuration. In addition to porosity, the material exhibits broad light emission centered at 617 nm with a full width at half‐maximum (FWHM) of 284 nm (0.96 eV). The recorded water stability is unparalleled for hybrid metal halide and perovskite materials, while the generation of porosity opens new pathways towards unexplored applications (e.g. solid‐state batteries) for this class of hybrid semiconductors.

Inside Cover: Porous and Water Stable 2D Hybrid Metal Halide with Broad Light Emission and Selective H2O Vapor Sorption (Angew. Chem. Int. Ed. 12/2023)

Inside Cover: Porous and Water Stable 2D Hybrid Metal Halide with Broad Light Emission and Selective H₂O Vapor Sorption (Angew. Chem. Int. Ed. 12/2023)

Innentitelbild: Porous and Water Stable 2D Hybrid Metal Halide with Broad Light Emission and Selective H2O Vapor Sorption (Angew. Chem. 12/2023)

Innentitelbild: Porous and Water Stable 2D Hybrid Metal Halide with Broad Light Emission and Selective H₂O Vapor Sorption (Angew. Chem. 12/2023)

Stabilization of Perovskite Lattice and Suppression of Sn2+/Sn4+ Oxidation via Formamidine Acetate for High Efficiency Tin Perovskite Solar Cells

AbstractTin halide lead‐free perovskite solar cells (TPSCs) have received tremendous research interest recently due to their nearly ideal bandgap, broad light absorption, non‐toxicity, and environmental friendliness. However, the uncontrollable crystallization process and the facile oxidation of Sn2+ limit the further increase of power conversion efficiency (PCE). To solve these problems, a series of acetates are introduced into the perovskite precursor solution to regulate the crystallization process. It is revealed that formamidine acetate (FAAc) has strong COSn coordination with Sn2+ compared with acetic acid (HAc) and methylammonium acetate (MAAc), which can stabilize the lattice structure, minimize defect states and suppress the oxidation of Sn2+. Meanwhile, benefiting from this coordination ability, it not only leads to large‐size colloidal clusters in precursor but also slows down the crystallization process and improves the crystallinity of tin halide perovskite films. The device with FAAc achieved an increased PCE from initially 9.84% to 12.43%, and it could maintain 94% of its initial value for 2000 h in N2 atmosphere. This work provides a feasible strategy for depositing high‐quality tin perovskite films with low defect density and lattice distortion, which will be crucial for related photovoltaics and other optoelectronic devices.

Organic Conjugated Trimers with Donor–Acceptor–Donor Structures for Photocatalytic Hydrogen Generation Application

AbstractOrganic donor–acceptor–donor (D–A–D) polymers or small molecules are widely investigated in organic solar cells due to their broad light absorption, narrow band gap, excellent charge mobility, and exciton seperation at the interface. However, studies of conjugated small molecules with D–A–D molecule structures as photocatalytically active materials are still rare. In this study, an unprecedented demonstration that photocatalytic activity can in fact be affected by tuning the D and A is given. Especially, the EBE trimer, comprising 3,4‐ethylenedioxythiophene (E) and benzothiadiazole (B) units, exhibits the best photophysical, chemical, and photocatalytic properties compared to other D–A–D combinations of D and A. Detailed kinetic studies show that all trimers in organic solution present relatively long‐lived and highly emissive photogenerated singlet excitons (τ = 4–13 ns; ϕem = 0.5–0.9) as judged by photoluminescence and transient absorption measurements, while in specific cases formation of long‐lived triplet states can be identified. Organic microparticles of the trimers are efficiently formed in aqueous solution by nanoprecipitation, and rapid photoinduced electron release/injection to the solvent is evidenced spectroscopically. The results indicate that organic small molecule structures with D–A–D structures pave a new pathway for photocatalytic solar‐to‐chemical energy conversion of novel small organic molecules.

Multi-Prismatic Hollow Cube CeVO4 with Adjustable Wall Thickness Directed towards Photocatalytic CO2 Reduction to CO.

Ternary orthovanadate compounds have received increasing attention due to their broad light absorption and diverse crystal structure. However, their multi-assembled crystal morphologies are limited mainly due to their initially polyatomic VO4 groups. In this study, multi-prismatic hollow cubic CeVO4 microstructures were fabricated by a one-step solvothermal method without any organic agents. The increase in wall thickness is in accordance with the radial direction of the quadrangular prism. Moreover, the overdose of the V precursor is favorable for the formation of hollow micro-cubic CeVO4, and the wall thickness changes from 200 to 700 nm. Furthermore, these CeVO4 microstructures were applied to photocatalytic CO2 reduction with a maximum CO generation rate of up to 78.12 μmol g-1 h-1 under visible light irradiation, which was several times higher than that of the other samples. This superior photocatalytic activity might be attributed to its good crystallinity and unique exposed interior structure. This study provides guidelines for the multi-assembled structure fabrication of ternary compounds and expands upon the exploration of the spatial structure of multivariate compounds.

S-scheme enhanced photocatalysis on graphitic carbon nitride functionalized with perylene tetracarboxylic diimide

It is a challenge to realize the catalytic conversion of ammonia by photocatalysis under mild conditions, because it is limited by the high photoinduced carrier recombination rate and low photo-absorption efficiency. Herein, we perform the condensation reaction of 3,4,9,10-perylenetetracarboxylic diimide (PTCDA) with graphitic carbon nitride (g-C3N4) nanosheets to obtain a novel organic semiconductor perylene tetracarboxylic diimide (PTCDI) modified g-C3N4 S-scheme heterostructure (named PTCDI@g-C3N4) via thermal-etching and bath process. The obtained PTCDI@g-C3N4 composite shows an obvious improvement in photocatalytic nitrogen reduction rate of 7308.9 μmol L−1 g−1h−1 with methanol under the Xe lamp irradiation, higher than g-C3N4 nanosheets (1215.3 μmol L−1 g−1 h−1). The excellent photocatalytic performance of PTCDI@g-C3N4 heterostructure is ascribed to two advantages: (1) The S-scheme heterojunction between organic semiconductor PTCDI and g-C3N4 nanosheets is profit to suppress carrier recombination and enhance electron utilization efficiency; (2) The utilization rate of g-C3N4 nanosheets to light was promoted due to the existence of PTCDI with broad visible light absorption. This work may help to provide a possibility to realize efficient photocatalytic nitrogen fixation by preparing organic-nonmetallic heterostructure through facile methods.