Low-energy Light Research Articles

Tuning Co-Operative Energy Transfer in Copper(I) Complexes Using Two-Photon Absorbing Diimine-Based Ligand Sensitizers.

Photocatalysis mediated by low energy light wavelengths has potential to enable safer, sustainable synthetic methods. A phenanthroline-derived ligand bathocupSani, with a large two-photon absorption (TPA) cross section was used to construct a heteroleptic complex [Cu(bathocupSani)(DPEPhos)]BF4 and a homoleptic complex [Cu(bathocupSani)2]BF4. The ligand and the respective homoleptic complex with copper exhibit two-photon upconversion with an anti-Stokes shift of 1.2 eV using red light. The complex [Cu(bathocupSani)2]BF4 promoted energy transfer photocatalysis enabling oxidative dimerization of benzylic amines, sulfide oxidation, phosphine oxidation, boronic acid oxidation and atom-transfer radical addition.

Metal-Free Oxidation of Acceptor-Donor Acylhydrazones into Diazo Compounds Using Phenyl Iododiacetate.

Aryl-ester acylhydrazones readily react with phenyl iododiacetate (PIDA) in methanol to produce the corresponding α-diazoesters with good to excellent yields (30 examples). The conditions have also been proven to be efficient in the synthesis of triazolopyridines. The crude mixture containing the diazo compound and acetic acid was also irradiated with low-energy blue LED light for a subsequent one-pot insertion of the in situ-generated carbene with AcOH to afford the respective acetates in high yields.

Optimizing Upconversion Quantum Yield via Structural Tuning of Dipyrrolonaphthyridinedione Annihilators.

Triplet-triplet annihilation upconversion (TTA-UC) is a photophysical process in which two low-energy photons are converted into one higher-energy photon. This type of upconversion requires two species: a sensitizer that absorbs low-energy light and transfers its energy to an annihilator, which emits higher-energy light after TTA. In spite of the multitude of applications of TTA-UC, few families of annihilators have been explored. In this work, we show dipyrrolonaphthyridinediones (DPNDs) can act as annihilators in TTA-UC. We found that structural changes to DPND dramatically increase its upconversion quantum yield (UCQY). Our optimized DPND annihilator demonstrates a high maximum internal UCQY of 9.4 %, outperforming the UCQY of commonly used near-infrared-to-visible annihilator rubrene by almost double.

Enhancing the Sensitivity and Spatial Imaging Resolution of a Hybrid X-Ray Imaging Screen via Energy Transfer at the ZnS (Ag) and a Thermally Activated Delayed Fluorescence Interface.

Novel scintillation materials have played an indispensable role in the recent remarkable progress witnessed for X-ray imaging technology. Herein, a high-performance X-ray scintillation screen was developed based on a highly efficient hybrid system combining inorganic ZnS (Ag) with thermally activated delayed fluorescence (TADF) scintillator materials via an interfacial energy transfer (EnT) mechanism. ZnS (Ag) has a high X-ray absorption capacity and functions as the initial layer for efficiently converting high-energy X-ray photons into low-energy visible light (acting as a sensitizer) while also serving as an energy donor. The TADF component, on the contrary, is an energy acceptor and forms an active scintillating layer. By harnessing TADF chromophores that can efficiently capture both singlet and triplet excitons, our composite material offers a remarkable spatial imaging resolution of 24 line pairs per millimeter, surpassing those of the majority of existing organic and inorganic scintillators. Further, our interfacial energy transfer strategy effectively amplifies the radioluminescence intensity of the TADF scintillator by a factor of 75, offering an outstanding light yield of 38,000 photons/MeV. This advancement represents a remarkable breakthrough in organic X-ray scintillation technology and is a notable achievement within the X-ray imaging field, paving the way for novel applications in medical imaging and security inspection.

Enhanced synergistic catalysis of bisphenol A in river water using an anti-aging photocatalytic membrane

Bisphenol A (BPA), as an endocrine disruptor, poses a potential threat to ecosystems and human health in aquatic environments. Membrane catalytic systems can accelerate the degradation of BPA and facilitate its conversion into harmless compounds. Nevertheless, the complex nature of the water environments and the limited stability of catalysts often result in challenges such as catalyst aging and deactivation. Herein, an anti-aging multifunctional AgFeO2 catalytic material with electron transfer membrane support was prepared for synergistic catalysis of low-energy LED light (12 W) excitation and peroxydisulfate (PDS) activation. The anti-aging photocatalytic membrane completely degraded 10 ppm of BPA within 30 min, and did not show significant aging after the long-term synergistic catalytic process. In addition, actual river water was employed to assess the aging process and catalytic efficiency in a practical environment. A 60.79 cm2 photocatalytic membrane completely purified 10 L of BPA polluted river water, while the total organic carbon content decreased by 50 %. This was mainly due to the synergistic catalytic effect of the membrane, which boosted photoelectron transfer through electron transfer shortcuts, thereby enhancing persulfate activation. Overall, the multifunctional membrane provides an effective strategy for achieving a long-lasting catalytic effect and controlling photocatalyst aging in practice.

Low-energy red light-emitting diode irradiation enhances osteogenic differentiation of periodontal ligament stem cells by regulating miR-146a-5p.

The study aimed to investigate the role of miR-146a-5p in osteogenesis of hPDLSCs irradiated with low-energy red LEDs. After irradiation with 5 J/cm2 red LED, miR-146a-5p expression was detected by real-time quantitative polymerase chain reaction (RT-qPCR), and osteogenic markers expression was determined by RT-qPCR and Western blotting. Alkaline phosphatase (ALP) activity was assessed by ALP staining, and mineralization was assessed by Alizarin Red staining, respectively. Lentiviral vectors were designed to regulate miR-146a-5p expression. Dual-luciferase reporter assay was performed to confirm the targeted relationship between miR-146a-5p and MAPK1. Short hairpin RNA (shRNA) was used to regulate MAPK1 expression. RT-qPCR and western blotting revealed that 5 J/cm2 irradiation elevated the levels of the osteogenic markers osterix (OSX) and bone sialoprotein (BSP) in hPDLSCs. miR-146a-5p is downregulated in hPDLSCs under the low-energy red LED light irradiation. miR-146a-5p underexpression markedly promoted the osteogenic potential of hPDLSCs. miR-146a-5p targeted MAPK1. 5 J/cm2 red LED irradiation rescued the inhibitory effects of upregulated miR-146a-5p on osteogenic differentiation, and the positive influence of red LED irradiation could be reversed by downregulated MAPK1. These findings confirm that miR-146a-5p is involved in the effect of LED irradiation on the osteogenic differentiation of hPDLSCs by targeting MAPK1. Red LED irradiation may be a potential clinical adjunct therapy for periodontal regeneration.

Photobiomodulation in Ophthalmology: A Comprehensive Review of Bench-to-Bedside Research and Clinical Integration.

Photobiomodulation (PBM), also known as low-level laser therapy, is an emerging therapeutic modality in ophthalmology, attracting increasing interest for its potential to manage a variety of ocular conditions. PBM employs low-energy light within the red and near-infrared spectrum to penetrate biological tissues, where it interacts with cellular chromophores. This interaction is believed to enhance mitochondrial function, boost adenosine triphosphate (ATP) production, and reduce oxidative stress, leading to improved cellular repair and tissue regeneration. Recent bench research has demonstrated PBM's efficacy in cellular and animal models, showing its ability to modulate inflammatory processes and promote healing in retinal and corneal diseases. For instance, in retinal models, PBM has been observed to reduce apoptosis and support cell survival under stress conditions. Similarly, studies in corneal models suggest that PBM can accelerate wound healing and reduce scarring. Clinical trials further corroborate these findings, revealing that PBM can enhance treatment outcomes in several ocular diseases, including age-related macular degeneration, diabetic retinopathy, and dry eye disease. Patients undergoing PBM have reported improvements in visual acuity, reduced retinal inflammation, and better tear film stability, highlighting its potential as an adjunctive therapy. This review also explores the integration of PBM into clinical practice, discussing current treatment protocols, safety considerations, and the latest advancements in PBM technology. By offering a holistic overview, the review aims to provide clinicians and researchers with valuable insights into PBM's role in modern ophthalmic care, emphasizing its potential to enhance treatment strategies and improve patient outcomes.

From MAX to MXene: A case study of Sc2TlC MAX phase, Sc2C pristine MXene, and surface-functionalized Sc2CT2 (T=O, F) MXenes

The MXenes-based two-dimensional (2D) materials have become a hotspot of recent research due to their exciting physical behavior. In this first-principles study, we investigate the Sc2TlC MAX phase and its 2D derivatives, focusing on the transformation of Sc2TlC into a Sc2C 2D sheet and the subsequent surface functionalization of Sc2C with oxygen (O) and fluorine (F). Investigations of the electronic structures reveal that the Sc2TlC MAX phase is metallic and nonmagnetic, while the conversion to the Sc2C pristine monolayer and surface functionalized Sc2CO2 induces significant changes in its electronic structure but retains its metallic behavior. On the other hand, functionalization of the Sc2C monolayer with F2 (such as Sc2CF2) evolves semiconductor-like behavior with an energy gap of magnitude 1.325 eV for the up-spin state and 1.227 eV for the down-spin state. The optimal optical absorption of ultraviolet (UV) for Sc2TlC MAX phase and Sc2C, Sc2CO2, and Sc2CF2 MXenes have been found as 13.8 × 105 cm−1, 49.17 × 104 cm−1, 81.39 × 104 cm−1, and 69. ×104 cm−1, respectively. Investigations of the optical properties reveal considerable reflection and absorption capabilities, particularly upon exposure to low-energy light photons, suggesting their potential for optoelectronic and energy harvesting applications.

Geometrical, elastic, electronic, phonon, and optical properties of Na3AgO2 from first-principles calculation

In this paper, the geometrical, elastic, electronic, phonon, and optical properties of Na3AgO2 have been systematically studied by first-principles calculation. The results show that Na3AgO2 is mechanically stable and has small compressibility. Na3AgO2 is an indirect band-gap semiconductor with weak interatomic interaction. The bandgap calculated by HSE06 is 2.314 eV, and that calculated by GGA is 1.261 eV. For Na3AgO2, in the valence band near the Fermi level, the curve peaks of TDOS at −2.11 eV and −0.885 eV are primarily composed of O 2p states, which hybridize the 4 d and 4p states of Ag. The conduction band mainly consists of the 4p, 4 d, and 5s states of Ag, while hybridizing a few 2p states of O and a few 2p and 3s states of Na. As can be seen from the phonon dispersion spectrum there is no negative phonon frequency in the whole Brillouin region, indicating the structure is stable. Mulliken bond population of Na3AgO2 shows that O–Ag bonds have strong covalency, O–Na bonds have strong ionic properties, Na–Na bonds and Na–Ag bonds are antibonding. Na3AgO2 has a small reflectivity and a small absorption coefficient in the direction of (100) and (010) and has good transparency. The transparency of blue-violet light in the (001) direction is not as good as that of low-energy visible light. The obtained results lead to the conclusion that Na3AgO2 is a promising p-type transparent conducting material and is expected to be applied in practice.

Photo- and Electrochemical Organic Transformations Involving Radical Pathway: A Retrospection of Our Green-Chemistry-Inspired Synthetic Endeavours

AbstractThis account summarises our recent efforts (2020 to mid-2024) in designing and developing a handful of promising organic transformations for accessing several diversely functionalized biologically relevant organic scaffolds by following the green-chemistry principles with a particular focus on the application of low-energy visible light and electrochemistry. Mechanistic studies of each of these reactions established the involvement of a radical pathway.1 Introduction2 Green-Inspired Organic Transformations2.1 Visible-Light-Driven Organic Synthesis2.1.1 Synthesis of Functionalized Dihydrofuro[3,2-c]chromenones2.1.2 Synthesis of Functionalized 2-(Aryl/alkylamino)-3-(aryl/alkylselanyl)naphthalene-1,4-diones and 2-(Arylamino)-3-(arylthio)naphthalene-1,4-diones2.1.3 Synthesis of Functionalized 6-(Arylthio/arylseleno)benzo[a]phenazin-5-ols2.1.4 Synthesis of Functionalized 3-(Alkyl/benzylthio)-4-hydroxy-2H-chromen-2-ones2.1.5 Synthesis of Functionalized 2-Hydroxy-3-oxo-2,3-dihydrobenzofuran-2-carboxamides and 2-Hydroxy-3-oxo-2,3-dihydrobenzofuran-2-carboxylates2.1.6 Synthesis of Functionalized 2-Hydroxyphenylated α-Ketoamides2.2 Electrochemical Organic Synthesis2.2.1 Synthesis of 3-Selenylated/Sulfenylated Derivatives of 2-Amino-1,4-naphthoquinones2.2.2 Synthesis of Functionalized 6-(Arylthio/Arylseleno)benzo[a]phenazin-5-ols2.2.3 Synthesis of Functionalized Alkyl 2-Hydroxy-3-oxo-2,3-dihydrobenzofuran-2-carboxylates3 Conclusions

Bi3+/Eu3+ Co‐Activated Multimode Anti‐Counterfeiting Material with White Light Emission and Orange‐Yellow Persistent Luminescence

AbstractTraditional anti‐counterfeiting luminescent phosphors are usually composed of single‐mode photoluminescence materials, which greatly limits the security of encryption by its static fluorescent pattern. Herein, multi‐mode luminescence properties are achieved including fluorescence and persistent luminescence (PersL) within single host by co‐doping Bi3+ and Eu3+ in CaNaSb2O6F (CNSOF). A tunable emission is observed from blue (Bi3+, 3P1→1S0) to white and then to orange‐yellow (Eu3+, 5D1→7F2 and 5D0→7F0, 1, 2, 3, 4) as the excitation schemes, environment temperatures and doping level are modulated. Impressively, the blue emission attributed to the Bi3+ rapidly disappears after stopping the excitation light irradiation, and only the intense orange‐yellow PersL produced by Eu3+ can be observed. And a possible model for the energy transfer and PersL mechanism is proposed by the investigation crystal structure and photoluminescence/PersL. A schematic of security logo and digital information encryption is demonstrated using the prepared samples, which shows the dynamic evolution of the emission color and PersL brightness. The excellent property of multiple color outputs, different decay processes, and external field stimulation modes (including low energy light, thermal, and mechanical stimuli) present in CNSOF:Bi3+, Eu3+ provides a fast, low‐cost, and effective method for advanced anti‐counterfeiting and information encryption applications.

Assembly of S-Scheme heterojunctions In2S3/Zr-bcu-22bipy44dc and In2S3/PCN-224: Polishing band states to boost highly efficient photochemical scavenging of X-, K- and KN-types reactive dyes and Cr(VI)

Remarkable capability in utilizing visible light and the low CB potential makes In2S3 appealing in assembling MOFs-based heterojunctions. To achieve dual-functional photocatalytic decontamination of Cr(VI) and dyes via low-energy light, the focus remains on assembly of advanced heterostructures based on water-stable Zr-MOFs and In2S3. Herein, Zr-bcu-22bipy44dc and PCN-224 were deployed to fabricate two novel heterojunctions In2S3/Zr-bcu-22bipy44dc (IS/2244) and In2S3/PCN-224 (IS/P224), respectively. Indeed, IS/2244–2 and IS/P224–2 (with 50 % mass ratio of Zr-MOFs) exhibit the optimized optical-electronic properties. The new findings confirm that IS/P224–2, assembled from visible light-sensitive PCN-224, displays higher photocatalytic REDOX abilities than IS/2244–2 in degrading X-, K- and KN-types reactive dyes (RR2, RB13 and RB21) and reducing Cr2O72- ions. The elimination efficiencies of IS/P224–2 towards RR2, RB13, RB21 and Cr(VI) have reached 93.9 %, 95.8 %, 89.4 % and 98.0 % under 500 W xenon lamp, providing accelerated kinetic rates of 7.32, 14.04, 40.2 and 23.67 times of PCN-224, 112.8, 19.95, 10.58 and 3.38 times of In2S3, 5.04, 1.02, 1.39 and 1.78 times of IS/2244–2, respectively, which have been well maintained even after four photocatalytic cycles. More prominently, its performance has surpassed that of some reported MOFs-based materials and other photocatalysts. Mechanism studies have confirmed the potential active radical species, carriers transfer path and S-Scheme talents of two heterojunction materials. This study offers a feasible avenue to design low-energy light-driven bifunctional photocatalysts for water environment remediation.

Asymmetric aggregation enables red-light CO2 reduction with tunable activity and selectivity by intermolecular electronic coupling

Photocatalytic CO2 reduction to value-added chemicals is a promising way to simultaneously mitigate environmental and energy issues. Integrating low-energy red light harvesting, fast charge separation, and robust CO2 activation in a photosystem is a crucial prerequisite for highly efficient CO2 photoreduction but remains a huge challenge. Herein, we constructed an aggregated [Ru(2, 2'-bipyridine)3]Cl2 (denoted as Ru(bpy)3Cl2) photosystem. Various characterizations combining molecular dynamic simulations and theoretical calculations confirm that the electronic coupling between adjacent Ru(bpy)3Cl2 molecules can induce orbital hybridization, thus broadening the light absorption edge to the red light region. Meanwhile, the asymmetric aggregation of Ru(bpy)3Cl2 enables exciton dissociation and charge transfer through a dipole polarization effect. Significantly, this dipole polarization can also upshift the d-orbital of Ni catalytic centers, greatly strengthening the activation of CO2 and lowering the formation energy barrier of COOH* intermediates. Consequently, the apparent quantum yield (AQY) of aggregates for CO2-to-CO reduction reaches 4.2% at 610 nm, significantly higher than the AQYs of other reported photosystems at wavelengths ≥ 600 nm. More importantly, the catalytic efficiency and selectivity of CO2 reduction can be rationally tuned by controlling the aggregated degrees of Ru(bpy)3Cl2. This work highlights the key role of Ru(bpy)3Cl2 aggregation in prompting red-light harvesting and CO2 activation, which may help boost CO2 photoreduction efficiency from a fresh perspective.

Deciphering the Effects of Different Types of Sunlight Radiation on Skin Function: A Review

Sunlight radiation is a fundamental component of our daily lives. Specifically, blue light as well as UV light appear to play a role in the development of oxidative stress, DNA damage, photoaging, and pigmentation through the chromophores in skin tissues. However, several skin problems like psoriasis, eczema, and atopic dermatitis can be avoided with short-duration exposures to low-energy blue light radiation or UV radiation. In addition, exploring the effects of blue light as well as UV radiation on skin is quite essential for the development of minimally invasive antiaging strategies and for the design of innovative cosmetic formulations in modern aesthetics and cosmetology. Thus, in this review, we present the advantages as well as the disadvantages of light radiation, with a special focus on blue light and UV radiation activity on the human skin. We also discuss the molecular action of blue light and UV radiation on human skin. Other types of light radiation are included to holistically approach the effect of light on human skin.

The research progress on photocatalytic performance of graphene-based nanocomposites

As soon as nanomaterials were discovered, they attracted a lot of attention because of their unique and excellent properties and became major hot research. They are regarded as the most promising materials in the 21st century. With the growth of industrial production, photocatalytic technology has been pursued as an efficient, green, and economical way of industrial production and treatment of pollution. However, the low light energy utilization of traditional semiconductor materials is a drawback that cannot be ignored. Graphene, as one of the most common and widely used 2D nanomaterials, has a special structure and characteristics that can effectively solve this problem. The paper briefly introduces the structure, properties, preparation method, and basic principle of photocatalysis of graphene. At the same time, a review is provided on the application of graphene-based composite materials in the field of photocatalysis, including dye degradation, photocatalytic treatment of other emerging pollutants, photocatalytic treatment of air pollutants, and water decomposition. By summarizing and integrating the photocatalytic properties of several graphene-based composites, this article lays the foundation and helps to discover new graphene composites.

A Nonlinear Photochromic Reaction Based on Sensitizer-Free Triplet-Triplet Annihilation in a Perylene-Substituted Rhodamine Spirolactam.

Nonlinear photochromic reactions that work with weak incoherent light are important for molecular operations with high spatial resolution and multiple photofunctions based on single molecules. However, nonlinear photochromic compounds generally require complex molecular design, restricting accessibility in various fields. Herein, we report nonlinear photochromic properties in a perylene-substituted rhodamine spirolactam derivative (Rh-Pe), which is synthesized from rhodamine B in facile procedures. Direct excitation of Rh-Pe produces the triplet excited state via the charge-transfer (CT) state. The triplet excited state causes triplet-triplet annihilation to bring the generation of the intensely colored ring-open form with nonlinear behavior. Furthermore, green- and red-light-induced photochromism was achieved in Rh-Pe using triplet sensitizers, although Rh-Pe can be directly excited only by ultraviolet and blue light. Our findings are expected to contribute to the development of photofunctional materials showing nonlinear behavior and low-energy light responsivity.

Visible-light-driven photocatalytic degradation of ibuprofen by Cu-doped tubular C3N4: Mechanisms, degradation pathway and DFT calculation

The copper-modified tubular carbon nitride (CTCN) with higher specific surface area and pore volume was prepared by a simple in-situ hydrolysis and self-assembly. Increased ∼4.7-fold and ∼2.3-fold degradation rate for a representative refractory water pollutant (Ibuprofen, IBP) were achieved with low-energy light source (LED, 420 ± 10 nm), as compared to graphitic carbon nitride (GCN) and tubular carbon nitride (TCN), respectively. The high efficiency of IBP removal was supported by narrow band gap (2.15 eV), high photocurrent intensity (1.10 μA/cm2) and the high surface -OH group (14.75 μg/cm3) of CTCN. According to analysis of the various reactive species in the degradation, the superoxide radical (•O2−) played a dominant role, followed by •OH and h+, responsible for IBP degradation. Furthermore, Fukui functions were employed to predict the active sites of IBP, and combined with the HPLC-MS/MS results, possible mechanisms and pathways for photocatalytic degradation were indicated. This study will lay an important scientific foundation and a possible new approach for the treatment of emerging aromatic organic pollutants in visible-light-driven heterogeneous catalytic oxidation environment.

Taxonomic Distribution of Major Insect Pest of Rabi Season at Jhansi (U.P.) Using Solar Powered Light Traps

The experiment was conducted at Bundelkhand University, Jhansi (UP) during the period March and April, 2021 to study the taxonomic distribution of insect pest species collected in Solar powered Light Traps model SMV- 8 and SMV- 9 using low energy light source i.e. 7w UV LED. According to taxonomic analysis, 8 insect species were recorded and they belong to four orders and eight families. Based on the number of species collected, the order Lepidoptera had the biggest collection (42 per cent), followed by the order Coleoptera with 3 species (40 per cent). The pyraliidae family has the most insect pests (25 per cent), followed by the Scarabaeidae family (19 per cent).

U-Net enhanced real-time LED-based photoacoustic imaging.

Photoacoustic (PA) imaging is hybrid imaging modality with good optical contrast and spatial resolution. Portable, cost-effective, smaller footprint light emitting diodes (LEDs) are rapidly becoming important PA optical sources. However, the key challenge faced by the LED-based systems is the low light fluence that is generally compensated by high frame averaging, consequently reducing acquisition frame-rate. In this study, we present a simple deep learning U-Net framework that enhances the signal-to-noise ratio (SNR) and contrast of PA image obtained by averaging low number of frames. The SNR increased by approximately four-fold for both in-class in vitro phantoms (4.39 ± 2.55) and out-of-class in vivo models (4.27 ± 0.87). We also demonstrate the noise invariancy of the network and discuss the downsides (blurry outcome and failure to reduce the salt & pepper noise). Overall, the developed U-Net framework can provide a real-time image enhancement platform for clinically translatable low-cost and low-energy light source-based PA imaging systems.

Iron(III) Carbene Complexes with Tunable Excited State Energies for Photoredox and Upconversion.

Substituting precious elements in luminophores and photocatalysts by abundant first-row transition metals remains a significant challenge, and iron continues to be particularly attractive owing to its high natural abundance and low cost. Most iron complexes known to date face severe limitations due to undesirably efficient deactivation of luminescent and photoredox-active excited states. Two new iron(III) complexes with structurally simple chelate ligands enable straightforward tuning of ground and excited state properties, contrasting recent examples, in which chemical modification had a minor impact. Crude samples feature two luminescence bands strongly reminiscent of a recent iron(III) complex, in which this observation was attributed to dual luminescence, but in our case, there is clear-cut evidence that the higher-energy luminescence stems from an impurity and only the red photoluminescence from a doublet ligand-to-metal charge transfer (2LMCT) excited state is genuine. Photoinduced oxidative and reductive electron transfer reactions with methyl viologen and 10-methylphenothiazine occur with nearly diffusion-limited kinetics. Photocatalytic reactions not previously reported for this compound class, in particular the C-H arylation of diazonium salts and the aerobic hydroxylation of boronic acids, were achieved with low-energy red light excitation. Doublet-triplet energy transfer (DTET) from the luminescent 2LMCT state to an anthracene annihilator permits the proof of principle for triplet-triplet annihilation upconversion based on a molecular iron photosensitizer. These findings are relevant for the development of iron complexes featuring photophysical and photochemical properties competitive with noble-metal-based compounds.