Long-wavelength Light Research Articles

Rise and Decay of Photoluminescence in Upconverting Lanthanide-Doped Nanocrystals.

Nanocrystals (NCs) doped with lanthanides are capable of efficient photon upconversion, i.e., absorbing long-wavelength light and emitting shorter-wavelength light. The internal processes that enable upconversion are a complex network of electronic transitions within and energy transfer between dopant centers. In this work, we study the rise and decay dynamics of upconversion emission from β-NaYF4 NCs codoped with Er3+ and Yb3+. The rise dynamics of the red and green upconverted emissions are nonlinear, reflecting the nonlinear nature of upconversion and revealing the mechanisms that populate the emitting states. The excited-state decay dynamics are nonexponential. We unravel the underlying decay pathways using photonic experiments. These reveal the contributions of different upconversion pathways visually, as each pathway exhibits a distinct response to systematic variation of the local density of optical states. Moreover, the effect of the local density of optical states on core-only NCs is qualitatively different from core-shell NCs. This is due to the different balance between feeding and decay of the electronic levels that produce upconverted emission. The understanding of the upconversion dynamics provided here could lead to better imaging and sensing methods relying on upconversion lifetimes or guide the rational optimization of the dopant concentrations for brighter upconversion.

Resolving the Trap Distribution of Chalcogenide-Based Heterojunctions via Optical Injection Deep Level Transient Spectroscopy.

Chalcogenide semiconductors have emerged as promising candidates for next-generation optoelectronics, mainly benefiting from their cost-effective processability, chemical versatility, and excellent stability. However, the device performance is limited by the complex defect characteristics, necessitating a detailed understanding of the defect density, types, and distribution. This study employs optical injection deep level transient spectroscopy to characterize the trap features of antimony bismuth sulfide-based heterojunctions. Photoexcitation offers the possibility to determine the spatial distribution of traps. It reveals distinct distributions of hole and electron traps. Short-wavelength light (570 nm) detects hole traps near the hole transport layer, while long-wavelength light (830 nm) identifies electron traps near the electron transport layer. Additional intermediate-wavelength tests (670 and 755 nm) and light field distribution simulation further elucidate the trap distribution. Transient absorption and transient photocurrent also support the non-uniform trap distribution within the chalcogenide-based photodiodes.

Tunable multi-peak emission solid-state fluorescent carbon dots: Luminescence regulation mechanism and application in single-component-based LEDs

The design of solid-state fluorescent carbon dots (CDs) with multi-peak emission has become an urgent challenge to be solved with the in-depth research of CDs in LEDs. Here, one- and two-component solid-state white light CDs are synthesized by microwave-assisted hydrothermal method using the biological pollutant cyanobacteria, respectively. The solid-state fluorescence quantum yield of the one-component CDs was as high as 41.8 %, and the solid-state fluorescence mechanism of CDs is discussed to be mainly attributed to the self-quenching-resistant feature of “core-shell” structure and the reabsorption/RET-induced long-wavelength red light emission, and attenuation of the short emission wavelength. For two-component white light CDs, blue- and red-light CDs are obtained by simple dialysis separation, realizing the fluorescence tunability. The different origins of their multi-peak emission are discussed: core, edge and surface states. The synthesis yields of CDs are up to 62 %, enabling stable gram-scale production. The white- and red-light CDs are used as phosphors to fabricate fluorescent films and cold, pure, and warm white- and red-light LEDs with good resistance to photobleaching and temperature stability and CRI of 84.4, 85.7 and 61.5.

Achieving near-infrared photocatalytic overall water splitting with singular crystalline C3N4 from semi-molten-salt treatment

Developing singular semiconductor photocatalyst for overall water splitting (OWS) is of significance for commercialization of solar-fuel-production technologies but is critically challenging due to the rigorous requirements for band structure and charge-utilization capability, especially under long-wavelength light. Herein, we report the development of a highly crystalline C3N4 photocatalyst for efficient OWS under near-infrared (NIR) irradiation (λ >700 nm). An effective semi-molten-salt approach with solid/liquid medium was used to treat the oxygen-containing precursor and to minimize undesired nitrogen defects that the traditional strategies always suffer from. The fully condensed structure with high crystallinity was therefore achieved for oxygen-incorporated C3N4 with NIR absorption. Benefiting from simultaneous realization of high crystallinity for efficient charge separation/migration and narrowed bandgap for broad light harvesting, synthesized singular C3N4 presented unprecedented OWS performances with hydrogen/oxygen evolution amount of 1.2/0.6 μmol over 30 h under NIR irradiation. This work provides a conceptual strategy for the design of advanced OWS-active photocatalysts.

Restoration of cone-circuit functionality in the regenerating adult zebrafish retina

Unlike humans, teleosts like zebrafish exhibit robust retinal regeneration after injury from endogenous stem cells. However, it is unclear if regenerating cone photoreceptors regain physiological function and integrate correctly into post-synaptic circuits. We used two-photon calcium imaging of living adult retina to examine photoreceptor responses before and after light-induced lesions. To assess functional recovery of cones and downstream outer retinal circuits, we exploited color opponency; UV cones exhibit intrinsic Off-response to blue light, but On-response to green light, which depends on feedback signals from outer retinal circuits. Accordingly, we assessed the presence and quality of Off- vs. On-responses and found that regenerated UV cones regain both Off-responses to short-wavelength and On-responses to long-wavelength light within 3months after lesion. Therefore, physiological circuit functionality is restored in regenerated cone photoreceptors, suggesting that inducing endogenous regeneration is a promising strategy for human retinal repair.

Effects of light colors on the growth, body color changes, and phototactic behaviors of green, purple, and white sea cucumbers, Apostichopus japonicus

The sea cucumber (Apostichopus japonicus) is a high valuable species in Chinese aquaculture. Light significantly impacts the life cycle of sea cucumbers. However, existing studies mainly focus on the effect of light intensity and photoperiod on adult green sea cucumbers, with fewer studies on light color and inconsistent results. Research on the photoreceptive responses of different color morphs is still insufficient. Therefore, this study aims to explore the physiological and behavioral effects of different light colors on various color morphs (green, purple, white) of sea cucumbers. The results showed that short-wavelength light inhibits sea cucumber growth, while long-wavelength light and darkness promote higher growth rates. Green sea cucumbers adapted best to light stress, followed by purple and white morphs. Purple sea cucumbers grew better under long-wavelength light and darkness. Under low light, color changes in sea cucumbers were minimal. Sea cucumbers exhibited negative phototaxis to all light colors, with stronger reactions to blue and purple light, leading to stacking behavior. They aggregated less under red and yellow light, using tentacle contact to reduce light exposure. White sea cucumbers showed the most aggregation under light. The results provide a theoretical basis for further research on sea cucumber photoreception, new insights into environmental adaptation, and information for aquaculture improvement.

Structure of the red-shifted Fittonia albivenis photosystem I

Photosystem I (PSI) from Fittonia albivenis, an Acanthaceae ornamental plant, is notable among green plants for its red-shifted emission spectrum. Here, we solved the structure of a PSI–light harvesting complex I (LHCI) supercomplex from F. albivenis at 2.46-Å resolution using cryo-electron microscopy. The supercomplex contains a core complex of 14 subunits and an LHCI belt with four antenna subunits (Lhca1–4) similar to previously reported angiosperm PSI–LHCI structures; however, Lhca3 differs in three regions surrounding a dimer of low-energy chlorophylls (Chls) termed red Chls, which absorb far-red beyond visible light. The unique amino acid sequences within these regions are exclusively shared by plants with strongly red-shifted fluorescence emission, suggesting candidate structural elements for regulating the energy state of red Chls. These results provide a structural basis for unraveling the mechanisms of light harvest and transfer in PSI–LHCI of under canopy plants and for designing Lhc to harness longer-wavelength light in the far-red spectral range.

A Nanoencapsulated Ir(III)-Phthalocyanine Conjugate as a Promising Photodynamic Therapy Anticancer Agent.

Despite the potential of photodynamic therapy (PDT) in cancer treatment, the development of efficient and photostable photosensitizing molecules that operate at long wavelengths of light has become a major hurdle. Here, we report for the first time an Ir(III)-phthalocyanine conjugate (Ir-ZnPc) as a novel photosensitizer for high-efficiency synergistic PDT treatment that takes advantage of the long-wavelength excitation and near infrared (NIR) emission of the phthalocyanine scaffold and the known photostability and high phototoxicity of cyclometalated Ir(III) complexes. In order to increase water solubility and cell membrane permeability, the conjugate and parent zinc phthalocyanine (ZnPc) were encapsulated in amphoteric redox-responsive polyurethane-polyurea hybrid nanocapsules (Ir-ZnPc-NCs and ZnPc-NCs, respectively). Photobiological evaluations revealed that the encapsulated Ir-ZnPc conjugate achieved high photocytotoxicity in both normoxic and hypoxic conditions under 630 nm light irradiation, which can be attributed to dual Type I and Type II reactive oxygen species (ROS) photogeneration. Interestingly, PDT treatments with Ir-ZnPc-NCs and ZnPc-NCs significantly inhibited the growth of three-dimensional (3D) multicellular tumor spheroids. Overall, the nanoencapsulation of Zn phthalocyanines conjugated to cyclometalated Ir(III) complexes provides a new strategy for obtaining photostable and biocompatible red-light-activated nano-PDT agents with efficient performance under challenging hypoxic environments, thus offering new therapeutic opportunities for cancer treatment.

Exploring the Origins and Evolution of Oxygenic and Anoxygenic Photosynthesis in Deeply Branched Cyanobacteriota.

Cyanobacteriota, the sole prokaryotes capable of oxygenic photosynthesis (OxyP), occupy a unique and pivotal role in Earth's history. While the notion that OxyP may have originated from Cyanobacteriota is widely accepted, its early evolution remains elusive. Here, by using both metagenomics and metatranscriptomics, we explore 36 metagenome-assembled genomes from hot spring ecosystems, belonging to two deep-branching cyanobacterial orders: Thermostichales and Gloeomargaritales. Functional investigation reveals that Thermostichales encode the crucial thylakoid membrane biogenesis protein, vesicle-inducing protein in plastids 1 (Vipp1). Based on the phylogenetic results, we infer that the evolution of the thylakoid membrane predates the divergence of Thermostichales from other cyanobacterial groups and that Thermostichales may be the most ancient lineage known to date to have inherited this feature from their common ancestor. Apart from OxyP, both lineages are potentially capable of sulfide-driven AnoxyP by linking sulfide oxidation to the photosynthetic electron transport chain. Unexpectedly, this AnoxyP capacity appears to be an acquired feature, as the key gene sqr was horizontally transferred from later-evolved cyanobacterial lineages. The presence of two D1 protein variants in Thermostichales suggests the functional flexibility of photosystems, ensuring their survival in fluctuating redox environments. Furthermore, all MAGs feature streamlined phycobilisomes with a preference for capturing longer-wavelength light, implying a unique evolutionary trajectory. Collectively, these results reveal the photosynthetic flexibility in these early-diverging cyanobacterial lineages, shedding new light on the early evolution of Cyanobacteriota and their photosynthetic processes.

Transparent metal-oxide photovoltaics for energy harvesting and storage for sustainable platforms

A transparent photovoltaic (TPV) energy harvesting method would provide more degrees of freedom for deployment on windows, buildings, vehicles, and surfaces with less soil dependency. This study designs a TPV-integrated energy storage system (capacitor charger) as a sustainable energy platform. The TPV device comprises a metal-oxide junction with a thin Si layer to enhance light utilization across a broad spectrum. Wide-bandgap metal-oxide-based materials absorb high-energy ultraviolet (UV) photons, while the Si layer captures longer wavelength lights due to the lower bandgap. The TPV structure (FTO/NiO/p+-Si/a-Si/n+-Si/AZO/ITO) exhibits an average visible transparency of 37 % and a power conversion efficiency of 4.97 % under 405 nm UV light illumination. The excellent electrical characteristics with a short-circuit current density of 10.1 mA/cm2 and open-circuit voltage value of 0.79 V allow TPVs to serve as a power source for rapidly charging capacitor banks in the energy storage unit. This PV-linked capacitor energy system can illuminate LED lamps, suggesting an on-site sustainable energy platform. The proposed Si-embedded TPV demonstrates electric power generation across broad wavelengths, enabling the bi-directional PV utilization of sunlight and indoor light sources for energy harvesting both day and night.

Ti‐Doped ZnO Thin Films‐Based Transparent Photovoltaic for High‐Performance Broadband and Wide‐Field‐of‐View Photocommunication Window

Transparent photovoltaics (TPVs) are crucial for developing next‐generation see‐through electronics. However, TPV devices (TPVDs) require wide‐bandgap materials that are typically only responsive to short wavelength (ultraviolet, UV) lights rather than visible lights. Is it possible to improve the TPV performance by harvesting the longer wavelength lights without degradation of transparency? It may be satisfied with the function of intermediate energy states, which can utilize the lower photon energy (longer wavelength light) by a two‐step transition. To achieve this, co‐sputtered Ti‐doped ZnO (Ti:ZnO) film‐based high‐performance TPVDs have been developed. Density functional theory analysis revealed the formation of intermediate energy states due to the hybridization of O 2p and Ti 3d orbitals in the Ti:ZnO system. The Ti:ZnO‐based TPVDs show 65% average visible transparency with a power production value of 655 μW cm−2. These devices exhibit good photodetection behavior under UV to visible illuminations with high responsivity and detectivity values of 1.85 A W−1 and 2.5 × 1013 Jones, respectively. Finally, a high‐performance UV to visible broadband and wide‐field‐of‐view photocommunication system is designed based on the TPVDs to generate the fast Morse code signal. Therefore, Ti doping in ZnO provides a good way to improve the device's functionality for futuristic applications.

Zinc oxide nanoparticles with catalase-like nanozyme activity and near-infrared light response: A combination of effective photodynamic therapy, autophagy, ferroptosis, and antitumor immunity

We prepared biocompatible and environment-friendly zinc oxide nanoparticles (ZnO NPs) with upconversion properties and catalase-like nanozyme activity. Photodynamic therapy (PDT) application is severely limited by the poor penetration of UV–Visible light and a hypoxic tumor environment. Here, we used ZnO NPs as a carrier for the photosensitizer chlorin e6 (Ce6) to construct zinc oxide–chlorin e6 nanoparticles (ZnO-Ce6 NPs), simultaneously addressing both problems. In terms of penetration, ZnO NPs convert 808 nm near-infrared light into 401 nm visible light to excite Ce6, achieving deep-penetrating photodynamic therapy under long-wavelength light. Interestingly, the ability to emit short-wavelength light under long-wavelength light is usually observed in upconversion nanoparticles. As nanozymes, ZnO NPs can catalyze the decomposition of hydrogen peroxide in tumors, providing oxygen for photodynamic action and relieving hypoxia. The enhanced photodynamic action produces a large amount of reactive oxygen species, which overactivate autophagy and trigger immunogenic cell death (ICD), leading to antitumor immunotherapy. In addition, even in the absence of light, ZnO and ZnO-Ce6 NPs can induce ferroptosis of tumor cells and exert antitumor effects.

Development of Two-Photon Super-Resolution Microscopy

Two-photon excitation microscopy enables in vivo deep-tissue imaging within organisms. This technique is based on two-photon excitation, a nonlinear optical process that uses near-infrared light for excitation, resulting in high tissue permeability. Notably, two-photon excitation occurs only near the focal plane; therefore, minimally invasive tomographic images can be obtained. Owing to these features, two-photon excitation microscopy is currently widely used in medical and life-science research, particularly in the domain of neuroscience for in vivo visualization of deep tissues. However, the use of long-wavelength excitation light in two-photon excitation microscopy has resulted in a larger focused spot size and relatively low spatial resolution, which is a limitation of this technique for further applications. Recent studies have described super-resolution microscopy techniques applied to two-photon excitation microscopy in an attempt to observe living organisms "as they are in their natural state" with high spatial resolution. We have also addressed this topic using an optical approach (two-photon stimulated emission depletion microscopy) and an image analysis approach (two-photon super-resolution radial fluctuation). Here, we describe these approaches together with a discussion of our recent accomplishments.

In-situ growth of Cs0·33WO3@ATO composite material with enhanced NIR shielding rate for energy-saving coating

Driven by the global goal of “carbon neutrality”, energy conservation, emission reduction and low-carbon development have become important research directions. Transparent thermal insulation materials can effectively shield near-infrared radiation while maintaining high visible light transmittance, making them widely applicable in building energy conservation. In this paper, antimony-doped tin oxide (ATO) and cesium tungsten bronze (CsxWO3, or CWO) are chosen to be composited in order to solve the problems of the poor shielding effect of ATO for short-wavelength near-infrared (NIR) light and the unsatisfactory shielding effect of CWO for long-wavelength NIR light. Therefore, in this study, we employed a one-step hydrothermal method to form a novel CWO@ATO core-shell structure to combine the advantages of both ATO and CWO. By adjusting the composite ratio of ATO and CWO, both the physical and electronic stucutres are effectively tuned to promote the optical modulation in a broad bandwidth. Enventually, the core-shell structured composite exhibit an excellent near-infrared blocking property, surpassing the pure ATO by 27.8 % in the wavelength region of 780∼1500 nm while improving by 14.9 % compared to CWO in the long wavelength between 1500 and 2500 nm. Furthermore, the prepared CWO@ATO core-shell structure repesents near-infrared shielding rate as high as 93.1 % in the full NIR spectrum, and possesses an overall thermal insulation coefficiency (THI) of 9.33 in the full range from 780 nm to 2500 nm, which is substantially larger than that of pure ATO and CWO by a factor of 2.37 and 3.05, respectively. This core-shell structure engineering realizes the utilization of complementary advantages of ATO and Cs0·33WO3 materials, providing a new method to improve the near-infrared performance of energy-saving glass coating, and having broad application prospects in the field of low-carbon buildings.

Cs-Doped WO3 with Enhanced Conduction Band for Efficient Photocatalytic Oxygen Evolution Reaction Driven by Long-Wavelength Visible Light.

Cesium doped WO3 (Cs-WO3) photocatalyst with high and stable oxidation activity was successfully synthesized by a one-step hydrothermal method using Cs2CO3 as the doped metal ion source and tungstic acid (H2WO4) as the tungsten source. A series of analytical characterization tools and oxygen precipitation activity tests were used to compare the effects of different additions of Cs2CO3 on the crystal structure and microscopic morphologies. The UV-visible diffuse reflectance spectra (DRS) of Cs-doped material exhibited a significant red shift in the absorption edge with new shoulders appearing at 440-520 nm. The formation of an oxygen vacancy was confirmed in Cs-WO3 by the EPR signal, which can effectively regulate the electronic structure of the catalyst surface and contribute to improving the activity of the oxygen evolution reaction (OER). The photocatalytic OER results showed that the Cs-WO3-0.1 exhibited the optimal oxygen precipitation activity, reaching 58.28 µmol at 6 h, which was greater than six times higher than that of WO3-0 (9.76 μmol). It can be attributed to the synergistic effect of the increase in the conduction band position of Cs-WO3-0.1 (0.11 V) and oxygen vacancies compared to WO3-0, which accelerate the electron conduction rate and slow down the rapid compounding of photogenerated electrons-holes, improving the water-catalytic oxygen precipitation activity of WO3.

Filter-Less Color-Selective Photodetector Derived from Integration of Parallel Perovskite Photoelectric Response Units.

Color-selective photodetectors (PDs) play an indispensable role in spectral recognition, image sensing, and other fields. Nevertheless, complex filters and delicate optical paths in such devices significantly increase their complexity and size, which subsequently impede their integration in smart optoelectronic chips for universal applications. This work demonstrates the successful fabrication of filter-less color-selective perovskite PDs by integrating three perovskite units with different photoresponse on a single chip. The variation in photoresponse is attributed to different quantities of SnO2 nanoparticles, synthesized through controlled ultrasonic treatment on the surface of the electron transportation layer SnS2, which selectively absorb short-wavelength light, thus increasing the relative transmittance of long-wavelength light and enhancing the photoresponse of the units to long wavelengths. By integrating any two units and deriving the formula for the wavelength to the responsivity ratio, a wavelength sensor is developed which can accurately identify incident light in the range of 400-700nm with a minimum error <3nm. Furthermore, the device integrating three units with different photoresponse can identify red, green and blue in polychromatic light to achieve color imaging with a relative error <6%. This work provides valuable insights into wavelength identification and color imaging of perovskite PDs.

Cu-doped KTN crystal with controllable, reversible, and fast photochromic properties: A superior electro-optical material for improving beam deflection performance

Improving the deflection performance of a beam deflector is urgently required to acquire optical signals for space laser communication and change the attitude and position of space targets and spacecraft. In this work, a Cu-doped potassium tantalate niobate (Cu-KTN) single crystal with fast photochromic and increased beam deflection properties is synthesized using the top-seeded solution growth method. When a Cu-KTN single crystal is irradiated with 405 nm light or ultraviolet (UV) light, the color changes from pale green to reddish brown. After light irradiation, the color gradually returns to yellowish green. Decolorization is accelerated under irradiation with green light or long-wavelength light, and the color changes to pale green. The origin of reversible photochromism reveals the fast valence change of Cu ions. In addition, ion doping improves the beam deflection angle of the secondary electro-optical effect of Cu-KTN (4.3 mrad, 1000 V) crystal compared with pure KTN (3.2 mrad, 1000 V). This study successfully synthesizes Cu-KTN single crystals with photochromic uses and establishes a new route for beam deflectors with significant deflection angles.

Red-Light-Driven Bifunctionalization of Styrene Derivatives.

A red-light-activated phthalocyanine ruthenium complex has been designed as a catalyst for the bifunctionalization of styrene derivatives. The combination of a trifluoromethylation agent resistant to nucleophiles and various nucleophiles facilitates the concurrent incorporation of a trifluoromethyl group and various functional groups onto the double bond of the substrate. This reaction demonstrates the utility of mild, low-energy, and highly transmissive long-wavelength light for intricate molecular transformations in a one-pot procedure.

Investigating the Influence of Varied Light-Emitting Diode (LED) Wavelengths on Phototactic Behavior and Opsin Genes in Vespinae.

The phototactic behavior of insects is commonly used to manage pest populations in practical production. However, this elusive behavior is not yet fully understood. Investigating whether the opsin genes play a crucial role in phototaxis is an intriguing topic. Vespinae (Hymenoptera: Vespidae) are a common group of social wasps that are closely associated with human activities. Efficiently controlling wasp populations while maintaining ecological balance is a pressing global challenge that still has to be resolved. This research aims to explore the phototactic behavior and key opsin genes associated with Vespinae. We found significant differences in the photophilic rates of Vespula germanica and Vespa analis under 14 different light conditions, indicating that their phototactic behavior is rhythmic. The results also showed that the two species exhibited varying photophilic rates under different wavelengths of light, suggesting that light wavelength significantly affects their phototactic behavior. Additionally, the opsin genes of the most aggressive hornet, Vespa basalis, have been sequenced. There are only two opsin genes, one for UV light and the other for blue light, and Vespa basalis lacks long-wavelength visual proteins. However, they exhibit peak phototaxis for long-wavelength light and instead have the lowest phototaxis for UV light. This suggests that the visual protein genes have a complex regulatory mechanism for phototactic behavior in Vespinae. Additionally, visual protein sequences have a high degree of homology among Hymenoptera. Despite the hypotheses put forward by some scholars regarding phototaxis, a clear and complete explanation of insect phototaxis is still lacking to date. Our findings provide a strong theoretical basis for further investigation of visual expression patterns and phototactic mechanisms in Vespinae.

Discovery of a novel photosensitizer based on the enediyne antibiotic N1999A2 and its application as a glutathione-activatable theranostic agent

Abstract The 2-naphthol derivative 2, which corresponds to the aromatic moiety of the enediyne antibiotic N1999A2, was found to degrade protein under irradiation with long-wavelength UV light in the absence of any additives. Structure–activity relationship studies of 2 indicated that 3, in which the primary hydroxyl group at the C5 position of 2 is modified with a t-butyldiphenylsilyl group, has strong protein photodegradation ability. Furthermore, the theranostic molecule 5 was designed and synthesized. Compound 5 comprises a disulfide moiety linked to the hydroxyl group at the C2 position of 3 and to the fluorescent molecule dicyanomethylene-4H-pyran (DCM) chromophore derivative 6. The disulfide moiety is cleaved in the presence of glutathione (GSH), 5 showed significantly reduced photolytic activity and fluorescence compared to 3 and 6, but produced 3 and 6 when reacted with GSH. 5 showed selective fluorescence and photocytotoxicity against cancer cells that highly express GSH.