Excitation wavelength-dependent emission is a unique photophysical channel with significant implications in analytical and biological applications; however, such phenomena remain rarely explored. To address this, carbon dots (CDs) were synthesized via a microwave-assisted method and systematically characterized using SEM, TEM, FTIR, XPS, UV-visible absorption, and fluorescence spectroscopy. Spectroscopic studies reveal that the emission from CDs strongly depends on the excitation wavelength, confirming the presence of energetically distributed and heterogeneous emissive surface states. These surface states enable a selective population of distinct excited states, thereby modulating the emission characteristics. The global analysis also identified three emissive pathways in the CDs. These pathways have a short lifetime of about 1 ns, an intermediate lifetime that corresponds to the intrinsic citrazinic acid emission (6.3 ns), and a long lifetime that can extend up to 10.8 ns. This provides further support for the presence of multiple surface states that contain rapidly decaying traps and emissive traps that have longer radiative lifetimes compared to free citrazinic acid. On the other hand, the sensing performance was also governed by excitation wavelength, indicating that different excited states possess varying electron transfer quenching efficiencies toward Hg2+ ions. The Stern-Volmer analysis and time-resolved fluorescence decay measurements reveal an electron transfer quenching mechanism, where reduced fluorescence lifetimes and negative free energy change values confirm thermodynamically favorable electron transfer from excited CDs to Hg2+ ions. Furthermore, the CDs exhibit reversible sensing behavior with l-cysteine, restoring fluorescence via the competitive chelation of Hg2+ ions, as supported by steady-state and time-resolved fluorescence measurements. Cytotoxicity and bioimaging studies have been performed on human lung carcinoma (A549) cells that reveal negligible toxicity and enable intracellular imaging of Hg2+ quenching and l-cysteine-mediated recovery. Overall, the obtained results on CDs establish a direct correlation between excitation-dependent photophysical properties and sensing mechanisms, providing a rational framework for the design of wavelength-dependent metal-ion detection and live-cell imaging applications.

Development of new and improved photoswitches for molecular photonics and photo‐pharmaceutics is an increasingly important research objective. Recently a promising family of photoswitches based on the rhodanine motif was described. Here, the photophysics of a typical example are investigated by ultrafast UV and IR spectroscopy and quantum chemical calculations. Remarkably, the photophysics are very different to and more complex than those of closely related monomethine photoswitches, which relax by ultrafast internal conversion to the electronic ground state. In the rhodanine photoswitch, the allowed Franck–Condon excited state also relaxes on a sub‐picosecond timescale, but the ground state is repopulated only after several hundred picoseconds. Instead, the Franck–Condon state relaxes through (at least) two intermediate states. These states are characterized by transient spectroscopy, and the reaction pathway is modeled by quantum chemical calculations. Comparison of calculated and measured IR data suggests that a triplet mediated isomerization pathway is responsible for the slow excited state dynamics. The triplet state is rapidly populated via coupling of a nearly degenerate nπ * state populated by ultrafast internal conversion from the bright ππ * state. This unexpected isomerization pathway has important implications for the synthesis, analysis, and application of rhodanine photoswitches.

In this paper, the intentional control of morphology and photophysical properties of a conjugated polydiarylfluorene, PODPF, in thin films is achieved through various systematic approaches including physical stretching when hosted in a highly elastic polymer, poly(vinyl butyral) (PVB) at various weight-to-weight ratios, and by varying the solvent. Microspectroscopic techniques were employed to monitor the resulting variations. Significant differences in the excitation and emission spectra are observed as functions of the concentration of PODPF mixed in the PVB film. This indicates the formation of different types of aggregates in these films through the coupling between dipoles with different relative orientations. Fluorescence anisotropy images show dramatic differences as a function of the extent of physical stretching of the film and as a function of PODPF concentration. Shifts in the emission spectra of the films as a function of the concentration in films cast from different solvents illustrate that the morphology of the films is highly dependent on the properties of the solvent from which the film is cast. The results highlight effective approaches for influencing the morphology and properties of conjugated polymers in thin films, with particular emphasis on the crucial role of solvent selection. Theoretical modeling is also employed to provide insight into the underlying principles governing these observed phenomena.

Trap states located below the conduction band edge are potentially key factors that control the photocatalytic activities of TiO2. Here, we used a time-resolved photoluminescence approach to characterize these trap states in an anatase TiO2. Direct excitation of trap sites was performed by laser excitation. When the excitation energy was below the band gap energy, the luminescence decay profile contained a more prominent fast decay component compared with that when the excitation energy was above the band gap energy. We attribute this finding to site-selective excitation of regions of deformed structure near the surface of the TiO2 particle.

Photovoltaic thin film solar cells based on kesterite Cu2 ZnSn(S, Se)4 (CZTSSe) have reached 13.8% sunlight-to-electricity conversion efficiency. However, this efficiency is still far from the Shockley-Queisser radiative limit and is hindered by the significant deficit in open circuit voltage (VOC ). The presence of high-density interface states between the absorber layer and buffer or window layer leads to the recombination of photogenerated carriers, thereby reducing effective carrier collection. To tackle this issue, a new window structure ZnO/AgNW/ZnO/AgNW (ZAZA) comprising layers of ZnO and silver nanowires (AgNWs) is proposed. This structure offers a simple and low-damage processing method, resulting in improved optoelectronic properties and junction quality. The ZAZA-based devices exhibit enhanced VOC due to the higher built-in voltage (Vbi ) and reduced interface recombination compared to the usual indium tin oxide (ITO) based structures. Additionally, improved carrier collection is demonstrated as a result of the shortened collection paths and the more uniform carrier lifetime distribution. These advances enable the fabrication of the first ITO-free CZTSSe solar cells with over 10% efficiency without an anti-reflective coating.

The alignment of chromophores plays a crucial role in determining the optoelectronic properties of materials. Such alignment can make interpretation of fluorescence anisotropy microscopy (FAM) images somewhat ambiguous. The time-resolved emission behaviour can also influence the fluorescence anisotropy. This is particularly the case when probing excitation energy migration between chromophores in a condensed phase. Ideally information concerning the chromophoric alignment, emission decay kinetics and fluorescence anisotropy can be recorded and correlated. We report on the use of polarised transmission imaging (PTI) coupled with both steady-state and time-resolved FAM to enable accurate identification of chromophoric alignment and morphology in thin films of a conjugated polydiarylfluorene. We show that the combination of these three imaging modes presents a comprehensive methodology for investigating the alignment and morphology of chromophores in thin films, particularly for accurately mapping the distribution of amorphous and crystalline phases within the thin films, offering valuable insights for the design and optimization of materials with enhanced optoelectronic performance.

Thermally activated delayed fluorescence (TADF) emitters, which convert nonemissive triplets into emissive singlets, have garnered tremendous impetus as next-generation organic electroluminescent materials. Employing donor-acceptor (D-A) designs to produce intramolecular charge transfer (ICT) states is considered an attractive strategy to effectively reduce the singlet-triplet (Delta E- ST) gap, thereby enhancing reverse intersystem crossing (rISC) in TADF emitters. Herein, we report two ICT chromophores (BP-1TPA and BP-2TPA) utilizing a rational design strategy based on a twisted biphthalimide acceptor core integrated with varying triphenylamine donors. We accomplish efficient TADF emission with a high photoluminescence quantum yield (PLQY) of similar to 80% at ambient conditions from poly(methyl methacrylate)-doped films of these chromophores. Twisting the acceptor core ensures the separation of natural transition orbitals, leading to small Delta E (ST) and generates an intermediate triplet excited state to facilitate rISC. The present study, therefore, sheds light on how delayed fluorescence can be realized from a simple twisted phthalimide core by rational molecular engineering and enables new insights toward exploring the aromatic imide class of molecules as potential organic light-emitting materials.

IntroductionNutrition is an essential part of gastroenterology specialist training. There is limited evidence of trainee experience in this area. The shorter training programme introduced in 2022 may lead to reduced exposure to this subspecialty. We aimed to explore and describe current nutrition training experiences, confidence and satisfaction to inform future improvements.MethodsGastroenterology trainees were invited to participate in an online survey from 20 May 2022 to 18 July 2022. The questionnaire consisted of 27 questions with a range of free-text and Likert scale responses.Results86 responses were received. 39.5% had undertaken an advanced training programme or core placement in nutrition. 52.9% of these felt 'fairly confident' or 'very confident' in managing intestinal failure vs 5.8% of those who had not completed a nutrition placement. Obesity and eating disorders management received the lowest ratings. Nutrition training was described as 'fairly important' or 'very important' by 98.8% and 47.0% included nutrition as part of their preferred future practice. 53.1% of ST6/7 trainees were 'fairly confident' or 'very confident' their training offered adequate experience in nutrition. Participants reported barriers including a lack of education and training opportunities, and limited early rotations offering nutrition training.ConclusionGastroenterology trainees believe nutrition training to be important. Nutrition placements increase trainee confidence, knowledge and experiences overall, but there is variability in this. Improved structuring of placements, increased educational opportunities and exposure to this subspecialty at an earlier stage are required to ensure competency in nutrition is reliably achieved during gastroenterology training.

Sodium (Na) doping is a well-established technique employed in chalcopyrite and kesterite solar cells. While various improvements can be achieved in crystalline quality, electrical properties, or defect passivation of the absorber materials by incorporating Na, a comprehensive demonstration of the desired Na distribution in CZTSSe is still lacking. Herein, a straightforward Na doping approach by dissolving NaCl into the CZTS precursor solution is proposed. It is demonstrated that a favorable Na ion distribution should comprise a precisely controlled Na+ concentration at the front surface and an enhanced distribution within the bottom region of the absorber layer. These findings demonstrated that Na ions play several positive roles within the device, leading to an overall power conversion efficiency of 12.51%.

The blend of polymeric donor PM6 and non-fullerene acceptor Y6 is high performing as both an active layer in organic photovoltaics and as a nanoparticulate photocatalyst for the renewable production of hydrogen gas. Despite the high performance of PM6:Y6 blends, many aspects of the photophysics of this material remain unclear. Here we present a detailed spectroscopic analysis of bulk heterojunction PM6:Y6 nanoparticles for photocatalytic hydrogen evolution over 11 orders of magnitude in time, ranging from tens of femtoseconds to hundreds of microseconds. We find that the excitation of Y6 primarily results in the formation of charges first in Y6 domains, followed by diffusion of Y6 holes to PM6 domains. Upon excitation of PM6, charges are generated through two mechanisms: (1) energy transfer to Y6 followed by exciton dissociation and back hole transfer to PM6, and (2) electron transfer to Y6 facilitated by an interfacial charge-transfer state. We use kinetic modelling to confirm these mechanisms and determine the rates of formation and recombination of charges. We also investigate the PM6:Y6 nanoparticles under photocatalytic conditions, and show that the Pt co-catalyst can accept both Y6 electrons and Y6 holes on relatively fast (<100 ps) timescales, and that the sacrificial electron donor ascorbic acid scavenges holes from both components on picosecond and microsecond timescales. The results highlight the critical importance of rapid free polaron formation in Y6 domains, and point towards harnessing this property of the Y-series and other non-fullerene acceptors to develop industrially viable organic hydrogen-evolution photocatalysts.

Exciton science sits at the intersection of chemical, optical and spin-based implementations of information processing, but using excitons to conduct logical operations remains relatively unexplored. Excitons encoding information could be read optically (photoexcitation-photoemission) or electrically (charge recombination-separation), travel through materials via exciton energy transfer, and interact with one another in stimuli-responsive molecular excitonic devices. Excitonic logic offers the potential to mediate electrical, optical and chemical information. Additionally, high-spin triplet and quintet (multi)excitons offer access to well defined spin states of relevance to magnetic field effects, classical spintronics and spin-based quantum information science. In this Roadmap, we propose a framework for developing excitonic computing based on singlet fission (SF) and triplet-triplet annihilation (TTA). Various molecular components capable of modulating SF/TTA for logical operations are suggested, including molecular photo-switching and multi-colour photoexcitation. We then outline a pathway for constructing excitonic logic devices, considering aspects of circuit assembly, logical operation synchronization, and exciton transport and amplification. Promising future directions and challenges are identified, and the potential for realizing excitonic computing in the near future is discussed.

Organic optoelectronics have received tremendous attentions in the past few decades, which are benefitting from the rapid development of organic semiconductors and their unique merits such as flexible design, low-cost production, and rich optoelectronic properties. Triplet excitons with two parallel electronic spins generated in the organic optoelectronic devices have significant effects on the device performance. In this review, a timely summary and brief discussion of the management and utilization of the triplet excitons in organic optoelectronic devices are given. We firstly summarized the studies and applications of triplet excitons in optical-to-electrical and electrical-to-optical devices, including solar cells, organic light-emitting diodes (OLEDs) and organic light-emitting transistors (OLETs). Particularly, the pioneering advances of triplet management in OLETs are reviewed for the first time. Additionally, two possible strategies for breaking the theoretical limit of internal quantum efficiency (IQE) in electroluminescent devices by fully taking the advantages of triplet excitons are proposed. Finally, the challenges and perspective of existing issues in this field for further improving the performance of optoelectronic devices and other related research directions are also provided.

Perovskite whentandemed with organic photovoltaics (OPV) for double-junctions have efficiencypotentials over 40%. However, there is still room for improvement suchas better current matching, higher fill factor, as well as lower voltage and fill factor losses in the top perovskite cell. Here weaddress the issue associated with the top perovskite cell by utilising anovel halogenated polycyclic aromatic hydrocarbon compound, 1-naphthylammoniumchloride (NA & horbar;Cl) playing dual roles of surface modification for the hole selectivelayer (HSL) and passivation of HSL/perovskiteinterface. Results of X-ray photoelectron spectroscopy and density functionaltheory calculations reveal that NA & horbar;Cl retains self-assembly property for the HSLwhile demonstrating high dipole moment and polarizability. This induces asurface dipole at the HSL/perovskite interface reducing the energetic barrierfor hole extraction by 210 meV thereby enhancing voltage output and fill factorof the device. Such scheme when implemented in a high bandgap (1.78 eV)perovskite solar cell, results in a respectable efficiency of 19.7% and thehighest fill factor of 85.4% amongst those of 1.78 eV perovskite cells reported.We have also achieved 23% cell efficient monolithic perovskite-OPV tandem withan impressive fill factor of 84%, which is the highest for perovskite-OPVtandem cells reported to-date.

The role of charge transfer states in multi-exciton mechanismshas recently become a point of discussion due to the difficulty associatedwith modeling their contributions accurately. Intermolecular packinghas been shown experimentally to heavily influence multi-exciton mechanisms,and therefore understanding how this affects the coupling is key tocontrolling these processes. Using a gas phase perylene dimer in aweakly coupled configuration as a case study, we employ two separatemethods to model the coupling between the bright and correlated triplet (1) TT states as a function of relative displacement.For singlet fission, displaced geometries are found to yield largecharge transfer contributions within a wavefunction overlap paradigm,unlike for aligned geometries. Triplet-triplet annihilationcharge transfer couplings are conversely very weak due to a largeenergy gap. We found that slipping of the dimer cofacial geometryis beneficial to both charge transfer-mediated processes within awavefunction overlap scheme. However, within a fragment excitationdifference (FED) scheme, a 1 & ANGS; slip is more beneficial than a2 & ANGS; one. The resulting rates for singlet fission are in the femtosecondrange, up to 22 ps(-1), while for triplet fusion theyare in the nanosecond range, up to 707 & mu;s(-1). By studying the dynamics of the triplet pair following singletfission, we show that the decorrelation time scale depends on thenature of the relative molecular motion, ranging from picosecondsfor fluctuations in the monomer orientations to microseconds for coplanarfluctuations. The direct comparison of the wavefunction overlap andFED methods yields an expected differential due to the method of calculation(linear-response vs multireference) but still strong agreement, suggestingthat the more exact wavefunction overlap method can be substitutedfor the FED method in larger systems with minimal loss in accuracyvs computational complexity. These results provide a good steppingstone for further investigations into singlet fission related problems,correlating well with experiments despite the weakly coupled natureof the dimer.

Evanescent wave-induced fluorescence spectroscopy (EWIFS) is a widely used technique for probing the interfacial behavior of different complex media in investigations of samples in the physical, chemical, and biological sciences. This technique takes advantage of the sharply decaying evanescent field, established following total internal reflection (TIR) at the interface of two media, for spatially identifying the photoluminescence characteristics of the sample. The generation of the evanescent field requires the refractive index of the second medium to be lower than that of the first, so a major disadvantage of this increasingly widely used spectroscopic technique is the inability to exploit the advantages of EWIFS to image a sample with a higher refractive index than the incident substrate medium. A proposed configuration in which a thin, low refractive index intermediate layer is established between the TIR substrate and a high refractive index sample is investigated. We illustrate that this arrangement does not afford the desired advantages of evanescent field-induced fluorescence measurements for investigating high refractive index media.

The development of efficient drug formulations for Parkinson's disease (PD) treatment is challenged by achieving pharmacokinetic profiles, reduced side effects, and better permeability through the blood-brain barrier (BBB). As nanoparticles may facilitate the delivery of drugs in the brain due to their high-loading capacity and ability to cross biological barriers, we designed two different types of selenium nanoparticles (SeNPs) that may increase the transport of drugs across the BBB and may act as antioxidants at the site of action. The SeNPs were functionalized with polyvinylpyrrolidone (PVP) and polysorbate 20 (Tween) and characterized in terms of their size, size distribution, shape, surface charge, and colloidal stability in relevant biological media. Their drug-loading capacity was tested using dopamine and L-DOPA as therapeutically active agents for PD. Thermodynamic analysis revealed that binding processes occurred spontaneously through hydrogen bond/van der Waals interactions or electrostatic interactions. The strongest interaction was observed between PVP-SeNPs and L-DOPA or dopamine, which was characterized by a binding constant several orders of magnitude higher than for Tween-SeNPs. However, the addition of human transferrin as a model plasma protein significantly reduced this difference, which indicates the crucial role of protein corona formation in the design of drug nanodelivery systems. In vitro evaluation by cell-free and cellular transwell models showed efficient internalization of SeNP-loaded L-DOPA/dopamine by human endothelial brain cells, while facilitated BBB permeability for L-DOPA, and dopamine was achieved using PVP-SeNPs. Overall, the high potential of SeNPs as drug-delivery vehicles in PD treatment was demonstrated.

We report a new composite material consisting of silver nanoparticles decorated with three-dimensional molecular organic cages based on light-absorbing porphyrins. The porphyrin cages serve to both stabilize the particles and allow diffusion and trapping of small molecules close to the metallic surface. Combining these two photoactive components results in a Fano-resonant interaction between the porphyrin Soret band and the nanoparticle-localised surface-plasmon resonance. Time-resolved spectroscopy revealed the silver nanoparticles transfer up to 37 % of their excited-state energy to the stabilising layer of porphyrin cages. These unusual photophysics cause a 2-fold current increase in photoelectrochemical water-splitting measurements. The composite structure provides a compelling proof of concept for advanced photosensitiser systems with intrinsic porosity for photocatalytic and sensing applications.

Supplementary Figure 1 shows the anti-mouse CTLA-4 DMAb design. Supplementary Figure 2 shows the efficacy of the recombinant 9D9 antibody in the Sa1N tumor model. Supplementary Figure 3 shows that the mouse anti-mouse CTLA-4 DMAb induces immune memory and protection from tumor re-challenge. Supplementary Figure 4 shows the efficacy of the mouse anti-mouse CTLA-4 DMAb delivered at an earlier time point. Supplementary Figure 5 shows that the anti-mouse CTLA-4 DMAb induces T cell infiltration into tumors. Supplementary Figure 6 shows the efficiency of CD4 and CD8 depletion antibodies.