Photophysical Characterization Research Articles

Paper Scintillator Incorporated with Scintillator-Silica Fine Powders: Photophysical Characterization and Proof of Concept Demonstration of Tritium Detection.

In order to decrease the generation of radioactive waste, it is of interest to develop a scintillator capable of absorbing tritiated solutions for efficient detection of low-energy β-particles from tritium. In this work, paper scintillator incorporated with scintillator-silica fine powders (FPs), which is composed of scintillator-silica nanoparticles (NPs) attached to silica FP, was fabricated and evaluated. The scintillator-silica NPs contained liquid scintillators benzoic acid, 2,5-diphenyloxazole (PPO), and 1,4-bis(5-phenyloxazol-2-yl) benzene (POPOP). Photophysical characterization was executed by means of photoluminescence, fluorescence lifetime, quantum efficiency, and radioluminescence under X-ray excitation. POPOP emission was confirmed by absorbing the emissions from benzoic acid and PPO. Radioluminescence results confirmed POPOP emission. Fluorescence lifetime analysis yielded a 1.29 ± 0.01 ns main fast decay (64.2%) combined with a 4.00 ± 0.04 ns slower decay (35.8%). The combined luminescence results suggested that most POPOP in the paper scintillator was solvated. At 301 nm, the average quantum efficiency from both faces of the paper scintillator was about 4%, and at 370 nm, it was about 11%. The paper scintillator detected 3H β-particles by dipping the paper scintillator into tritiated water without a liquid scintillator. The counting efficiency depended on water content in the paper scintillator, and it increased to above 10% for tritium activity less than 200 dpm since it was preferentially adsorbed by vapor pressure isotopic effect and isotopic exchanged tritium on the surface of the scintillator-silica FP in the paper scintillator.

Thermal stability and flexible X-Ray scintillation screen through in-situ assembling Cs3Cu2Cl5 nanocrystals in polymer matrix

Copper-based halides have emerged as promising scintillator materials for X-ray imaging, attributed to their favorable photophysical characteristics, such as negligible self-absorption, high light output, and fast decay. Within this category of materials, Cs3Cu2Cl5 composite polymer scintillator films stand out, delivering excellent performance as flexible X-ray detector screens. However, severe scattering and light degradation induced by the inevitable agglomeration during recombination restricted the application in high-resolution and flexible X-ray imaging. In this study, a Cs3Cu2Cl5@PMMA film prepared by in-situ growth strategy is successfully developed, which represents uniform area, adjustable flexibility and excellent scintillation performance. The prepared large-area film exhibits green emission at 527 nm, with a high light yield, low detection limit and excellent spatial resolution. Meanwhile, the Cs3Cu2Cl5@PMMA film exhibits a remarkable degree of flexibility, enabling imaging applications on non-planar surfaces. Furthermore, it also demonstrates excellent resistance to high temperature environment, maintaining its high-quality imaging performance at 403 K.

Heavy atom effect boosts the achievement of ultra-efficient long afterglow room temperature phosphorescent carbon point composites: An enhanced approach

In recent years, room temperature phosphorescent (RTP) materials have experienced rapid growth due to their enduring luminescence, high resolution, and other distinctive characteristics. Simultaneously, carbon dots (CDs) have gained popularity across various disciplines for their efficient luminescence, straightforward synthesis, and environmental friendliness. In this study, we successfully synthesized a range of high-performance carbon dot materials using a simple one-step hydrothermal method. Through detailed morphological and photophysical characterizations, we discovered that these materials exhibited a remarkable phosphorescence quantum yield of up to 53.15 %, an impressive feat for both metal and non-metal carbon dot materials. Furthermore, we explored the enhancing effect of the heavy atom on ultra-efficient long afterglow RTP carbon dot composites and experimentally validated its effectiveness. Finally, we applied these materials to information encryption technology, offering novel ideas and methods for RTP material applications. This research not only opens new avenues for the development of carbon dot materials but also provides a promising direction and outlook for their future use.

Revealing the ESIPT process in benzoxazole fluorophores within polymeric matrices through theory and experiment.

The impact of the polymeric matrix on the photophysical characteristics of monomeric dyes responsive to excited-state intramolecular proton transfer (ESIPT) was investigated through UV-Vis absorption as well as steady-state and time-resolved emission spectroscopies. For this purpose, two benzoxazole monomers (M1 and M2) with acryloyl groups at different positions in their molecular structures were employed to facilitate covalent bonding within a styrene chain. Our findings reveal significant variations in their excited-state properties due to the proximity of the acryloyl groups, which affects the energy barrier of the ESIPT reaction, the emission wavelength, and the balance between the normal and tautomeric forms. The experimental results were corroborated through theoretical investigations at the DFT/TDDFT level, specifically using the B3LYP-D3/def2-TZVP methodology. Three notable observations emerged: donor/acceptor groups at the meta/para positions induced electron distribution changes, causing red-shifted emission for M2; in the polymer film, particularly in PM1, intramolecular hydrogen bond deactivation favored N* emission over T* emission; and the zwitterionic character of the T* species. This study underscores the advantages of functionalization in polymers, which can lead to colorless films and prevalent N* or T* emission, and contributes valuable insights into molecular design strategies for tailoring the photophysical properties of polymeric materials.

Synthesis of Phosphorus/Arsenic Tridentate Ligands and Their Application for Luminescent Copper (I) Halide Complexes

AbstractWe synthesized arsenic analogs of a tridentate PPP ligand, bis[2‐(diphenylphosphino) phenyl] phenylphosphine, achieving yields of 40 % to 71 %. Additionally, we prepared copper (I) halide (CuX, X=Br, I) complexes with these ligands, with yields between 43 % and 84 %. Using both experimental and computational methods, we examined their structures and photophysical characteristics. Single crystal X‐ray diffraction showed that all eight complexes had distorted tetrahedral geometries. These complexes exhibited photoluminescence with emission bands peaking from 506 nm to 551 nm and quantum yields up to 0.92 at room temperature. Emission lifetimes varied and showed no direct correlation with quantum yields or wavelengths. Physical manipulation and solvent variations significantly altered their photoluminescent properties. DFT and TD‐DFT calculations revealed that higher arsenic content increased spin‐orbit coupling constants, with iodide complexes performing better than bromide ones due to heavier elements enhancing spin‐orbit coupling. Substituting phosphorus with arsenic significantly affected the luminescence quantum yield and lifetime, demonstrating the heavy‐atom effect of arsenic. The position of arsenic in the ligands critically influenced the photophysical outcomes of the CuX complexes.

New conjugated copolymer MEH-PPV-P3HT with donor-acceptor system for organic optoelectronics applications: Experimental and theoretical study

Donor-acceptor architecture was designed of new diblocks copolymer MEH-PPV-P3HT synthesis. The new copolymer was elaborated through oxidative pathway. The correlation structure-properties and their potential photophysical characteristics of the obtained material were reported utilizing several characterization analyses (InfraRed, Raman, TGA, UV visible spectroscopy, as well as PL and TRPL). To define the model's geometric structure, vibrational, and optoelectronic properties of the studied copolymer, Density Functional Theory DFT and Time-dependent Density Functional Theory TD-DFT approach were carried out. The obtained copolymer exhibits great thermal stability and substantial absorption in the visible range. An energy gap lower than the original materials by the amount of 1.74 eV which proves the presence of the charge transfer process. In addition, due to Forster energy transfer from the MEH-PPV to the P3HT an enhancement of the exciton average lifetime was detected. The obtained results from the copolymer characterization suggest a potential for application in organic optoelectronic devices. A good accordance between experimental and theoretical results based DFT calculations is obtained.

Luminescence under UV(A, B and C) and sunlight exposure of tetrakis Tb3+ carboxylate complexes doped in different polymers

New tetrakis Lanthanide(III) carboxylate-based complexes (Ln3+: Eu and Tb) were successfully synthesized via a facile one-pot method with flufenamic acid (fluf) as ligand and benzimidazole (Bzim) or 1-ethyl-3-methylimidazole (C2mim) as counterions. In addition, the Q[Tb(fluf)4] complexes (Q+: Bzim and C2mim) were doped into polymethylmethacrylate (PMMA), polystyrene (PS), polycaprolactone (PCL) and poly(9-vinylcarbazole) (PVK) polymeric matrices at a 1 % (w/w) concentration and revealed highly desirable photophysical features such as wide range excitation wavelengths for the PMMA and PCL matrices and a very uncommon emission under sunlight exposure arising from the Tb3+ ion for the PMMA material. Thus, the tetrakis compounds with general formula Q[Ln(fluf)4] were characterized by elemental and thermal analysis, ESI-MS mass spectrometry, and FTIR absorption spectroscopy. The PMMA:(1 %)Q[Tb(fluf)4] doped films revealed higher thermal stability than the complexes. The tetrakis Eu3+ complex with Bzim as counterion shows no luminescence either for room or low temperature due to a highly operative low-lying ligand to metal charge transfer (LMCT) state quenching, while the corresponding C2mim-based analogous complex reveals some weak intensity emission, showing very low intrinsic quantum yield (QEuEu) values. On the other hand, the corresponding Tb3+ compounds presented bright green emission for the solid-state complexes and, particularly, for the PMMA:(1 %)Q[Tb(fluf)4] doped films when excited at UVA, UVB, and UVC radiation. Moreover, when the doped PMMA films are exposed to sunlight radiation in an open external environment, a bright green emission arising from the 5D4 → 7F5 transition from the Tb3+ ion can be seen. In this way, these optical results suggest that the PMMA:(1 %)Q[Tb(fluf)4] luminescent photonic materials can act as versatile and efficient light-converting molecular devices (LCMDs).

Systematic Engineering of Near-Infrared Small Molecules Based on 4H-Cyclopenta[1,2-b:5,4-b']dithiophene Acceptors for Organic Solar Cells.

Nonfullerene acceptors (NFAs) have emerged as tremendous materials, efficiently advancing bulk-heterojunction organic solar cells (OSCs) technology. Unlike their fullerene counterparts, NFAs offer the unique advantage of finely tunable electronic energy levels and optical characteristics, which correspond to substantial enhancement in power conversion efficiency of OSCs. Herein, we have introduced a new series of near-infrared NFAs (AY1-AY8) to advance this technology further. Our research deeply investigates the structure-property relationship and thoroughly explores the optical, optoelectronics, photophysical, and photovoltaic characteristics of a synthetic reference molecule (R) and the modeled AY1-AY8 NFAs series. We performed advanced quantum chemical simulations using density functional theory (DFT) and time-dependent DFT methods. Additionally, we also estimated key geometric characteristics such as frontier molecular orbitals, hole-electron overlap, density of states, molecular electrostatic potential, molecular excitation and binding energies, transition density matrix, and reorganizational energy of electrons and holes and compared them with those of a synthetic reference molecule (R). Our findings show that all designed materials (AY1-AY8) exhibit red-shift absorption, improved electronic charge mobility, and low binding and excitation energies compared to R. Notably, these designed materials (AY1-AY8) display significantly narrower electronic energy gaps (E g 1.89-1.71 eV), indicating enhanced charge shifting from the highest occupied molecular orbital to lowest unoccupied molecular orbital and broadening of the absorption spectrum. Moreover, we also revealed a comprehensive study of the donor/acceptor complex of PTB7-Th/AY8 to understand charge shifting between donor and acceptor molecules. Therefore, we strongly recommend this designed (AY1-AY8) series to the experimentalists for the future development of highly efficient OSC devices.

Advancing optoelectronic characteristics of Diketopyrrolopyrrole-Based molecules as donors for organic and as hole transporting materials for perovskite solar cells

A stable and efficient hole-transport material (HTM) is crucial for high-performance perovskite solar cells (PSCs). A 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (Spiro-MeOTAD) being used widely to prepare highly efficient PSCs. However, Spiro-MeOTAD has some limitations due to its complex synthesis, which increases its cost, and it also requires dopants to improve its performance. Therefore, we designed thirteen unique small-molecule-based HTMs (MK1-MK13), which are easy to synthesize, highly cost-effective, and don’t require dopants to prepare efficient PSCs. Their electrical and optical properties are then investigated theoretically using advanced quantum chemical approaches. The designed molecules showed lower energy gaps and improved optical and optoelectronic characteristics because of the improved phase inversion geometry. The detailed photo-physical and optoelectronic characteristics have been studied using density functional theory (DFT) and time-dependent (TD-DFT) calculations. Moreover, we investigated the impact of holes and electrons and the density of states, open-circuit voltage, frontier molecular orbital, transition density matrix, and other structural and photovoltaic characteristics of these materials. Among these, the MK3 molecule possesses the much narrower optical band gap of 1.04 eV and absorbance (λ max) of 684 nm, respectively. In addition, a profound investigation of the MK3/PC61BM blend shows excellent charge transfer at the acceptor–donor interface. Therefore, our proposed technique is necessary for generating appropriate photovoltaic materials for efficient optoelectronic devices and is helpful in further advancing the field.

Synthesis and Photophysical Characterization of Fluorescent Naphtho[2,3-d]thiazole-4,9-Diones and Their Antimicrobial Activity against Staphylococcus Strains.

The chemical reaction of 2-(methylsulfinyl)naphtho[2,3-d]thiazole-4,9-dione (3) using different amines, including benzylamine (4a), morpholine (4b), thiomorpholine (4c), piperidine (4d), and 4-methylpiperazine (4e), produced corresponding new tricyclic naphtho[2,3-d]thiazole-4,9-dione compounds (5a-e) in moderate-to-good yields. The photophysical properties and antimicrobial activities of these compounds (5a-e) were then characterized. Owing to the extended π-conjugated system of naphtho[2,3-d]thiazole-4,9-dione skeleton and substituent effect, 5a-e showed fluorescence both in solution and in the solid state. The introduction of nitrogen-containing heterocycles at position 2 of the thiazole ring on naphtho[2,3-d]thiazole-4,9-dione led to large bathochromic shifts in solution, and 5b-e exhibited orange-red fluorescence with emission maxima of over 600 nm in highly polar solvents. Staphylococcus aureus (S. aureus) is a highly pathogenic bacterium, and infection with its antimicrobial-resistant pathogen methicillin-resistant S. aureus (MRSA) results in serious clinical problems. In this study, we also investigated the antimicrobial activities of 5a-e against S. aureus, MRSA, and S. epidermidis. Compounds 5c with thiomorpholine group and 5e with 4-methylpiperazine group showed potent antimicrobial activity against these bacteria. These results will lead to the development of new fluorescent dyes with antimicrobial activity in the future.

Synthesis and characterization of a xanthene-based molecular probe to detect triphosgene in solution and vapor phases

The ability of a detection approach to direct a visible and easy-to-monitor characteristic is an important aspect of molecular-level detection. From this viewpoint, we developed the molecular probe Xanth-Py, which allows us to visually detect triphosgene (TPG) by modulating the probe's photophysical characteristics. Since Xanth-Py exhibits a strong fluorescence, its interaction with TPG causes the non-radiative decay of the probe. As TPG concentrations increase, the fluorescence intensity decreases linearly, leading to a nanomolar level detection limit. The interaction of Xanth-Py with TPG accompanied a color change from pink to blue, enabling a visible detection protocol. Probe-coated paper strips have been used as an inexpensive detection tool for vapor-phase TPG detection, revealing the potential of the Xanth-Py. Further, triphosgene has been detected using a smartphone-assisted RGB analysis tool in conjunction with a portable UV-light source device.

DPPM-Bridged Binuclear Pt(II) Pincer Complexes: Chemistry, Structure, and Photophysics in Solution Revisited.

A series of luminescent binuclear ([dppm{Pt(NNC)}2]2+) and mononuclear ([PPh3Pt(NNC)]+) complexes containing pincer ligands were synthesized and characterized. Photophysical characteristics of both types of complexes were studied in dichloromethane solution. In the solid phase, the binuclear compounds adopt a syn configuration where the {Pt(NNC)} fragments are held together due to intramolecular Pt-Pt bonding and π-stacking of the pincer ligand aromatic systems. Analysis of the complexes' molecular structure in solution by multinuclear NMR spectroscopy showed that the stacked intramolecular configuration is retained in fluid media, which is in complete agreement with a considerable red shift of the emission wavelength due to formation of the intramolecular Pt-Pt bond, leading to the transformation of an emissive excited state to 3MMLCT. It was also found that triethylamine quenches the emission of both types of complexes; the mechanism of quenching is a combination of dynamic and static channels of excited-state deactivation. In the case of binuclear complexes, deprotonation of the dppm methylene bridge by triethylamine also contributes to the chromophore quenching. To explain the observed chemistry of binuclear complex interactions with Et3N, a chemical equilibrium scheme was suggested, which was confirmed by quantitative monitoring of the 31P signal variations as a function of triethylamine concentration.

Interplay between Theory and Photophysical Characterization in Symmetric α-Substituted Thienyl BODIPY Molecule.

4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-based molecules have emerged as interesting materials for optoelectronic applications due to the possibility to easily fine-tune their photophysical and optical properties, dominated by two main absorption bands in the visible range. However, no studies have been reported on the nature of these spectral features. By means of ultrafast spectroscopy, we detect intramolecular energy transfer in a spin-coated film of di-thieno-phenyl BODIPY (DTPBDP) dispersed in a polystyrene matrix after pumping the high-energy absorption band. The same effect is not present upon pumping the lowest-energy band, which instead allows the achievement of efficient amplified spontaneous emission. Density functional calculations indicate the different nature of the two main absorption bands, explaining their different photophysical behavior.

Simultaneous photocatalytic hydrogen peroxide production and pollutant degradation via bipyridine-based polyimide covalent organic framework

Covalent organic framework (COF) photocatalysts for hydrogen peroxide (H2O2) production are receiving significant attention because of the ever-increasing demand for H2O2. Despite the redox-active property and notable photophysical characteristics of polyimide (PI), the potential of PI-based COFs (PICs) for photocatalytic H2O2 production remains unexplored. Herein, we present a dual redox-active bipyridine-containing PIC (PIC-BPY) as an efficient photocatalyst for H2O2 production. PIC-BPY demonstrated exceptional performance by achieving an H2O2 production rate of 2772 μmol gcat.−1, which is three times higher than its biphenyl-based counterpart. We elucidated the reaction pathway through a series of scavenger tests and electron spin resonance analysis, thereby confirming the additional active role of BPY along with that of PIC framework. Furthermore, we harnessed hydroxyl radicals generated during photocatalysis to explore the potential of PIC-BPY for concurrent pollutant degradation and H2O2 production.

Implication of carbohydrazide chemosensors in selective sensing of Fe(III) and construction of molecular devices

Two new and two reference sensors L1-L2 and R1-R2, respectively, based on the hydrazide core were synthesized in good yields (70–86 %). A variety of analytical methods, including NMR, HRMS, and single-crystal XRD, were used to characterize these sensors. Cyclic voltammetry, UV–visible absorption, and emission spectroscopies were then used to confirm the electrochemical and photophysical characteristics of these sensors. Moreover, theoretical calculations at the level of DFT and TD-DFT were carried out to compare the experimental findings with the theoretical ones. The sensors were found to exhibit luminescence attributed to singlet ligand-centered (1LC) transitions. Based on their luminescent properties and the previous literature reports where structurally analogous sensors have been used for the detection of metal ions, these sensors were investigated as selective chemosensors for Fe(III) detection, with a "turn-off" fluorescence behaviour in a binding stoichiometry of 1:1 = sensor:M(III) [M = Fe(III)] with a limit of detection of 2.71–39 µM, or 0.15–2.81 ppm. The mechanistic details regarding the sensing of Fe(III) ion by the sensors was provided by NMR, IR, XPS and UV-visible absorption spectroscopic studies. To increase the usefulness of the sensors, L2 was also applied for the successful fabrication of the molecular logic gate and molecular lock keypad. Paper strip test and sensing of Fe(III) contaminated water by the sensors accounted for the practical applicability of the sensors in real life.

The influence of positional isomerism of a cyano group of pyrene-based rod-like mesogens on mesomorphism, dual-state emission and multiple applications

Two novel cyanostilbene-based rod-like mesogens consisting of one terminal pyrene and one terminal alkyl chain were prepared by Suzuki coupling and Knoevenagel reactions. The influence of the positional isomerism of the cyano group of cyanostilbene unit on the liquid crystalline characteristics, photophysical characteristics, and mechanochromism characteristics was studied by using polarized optical microscopy, differential scanning calorimetry, X-ray diffraction, absorption spectra, photoluminescence spectra, density functional theory calculation and time-dependent density functional theory calculation. The mesogen in which the cyano group is adjacent to the phenylpyrene unit exhibits a monotropic smectic C phase, whereas the mesogen in which the cyano group is far away from the phenylpyrene unit exhibits an enantiotropic smectic C phase. The mesogen in which the cyano group is adjacent to the phenylpyrene unit exhibits more distinct positive solvatochromism due to more distinct intramolecular charge transfer. The mesogen in which the cyano group is adjacent to the phenylpyrene unit exhibits aggregation-induced emission behavior, but the mesogen in which the cyano group is far away from the phenylpyrene unit exhibits dual-state emission behavior. Reversible mechanochromism behavior could be achieved in both mesogens due to twisted molecular configurations. In addition, the rewritable luminescent paper and bioimaging applications were also achieved. These results demonstrated that the distinct molecular design could endow organic molecules with multifunctional properties and potential applications.

Monometallic heteroleptic complexes of Dy(III) ion incorporating β-diketone and ancillary moieties: Photophysical and electrochemical analyses

Several luminescent ternary dysprosium complexes were synthesized and examined using diketone ligand 1,3-diphenylprop-1,3-dione (DPD) and various auxiliary ligands. Spectroscopic analysis was carried out to determine the structural and photophysical features of Dy (III) complexes. IR and proton NMR spectroscopic studies suggested the bonding of chelating moieties to the metal ion through oxygen and nitrogen atom. The optical and electronic band gap is evaluated which proposed the conducting behaviour of dysprosium complexes. Upon excitation with UV radiation, three distinct emission peaks of the Dy (III) ion are appeared at about 485 nm (J = 15/2), 575 nm (13/2) and 664 nm (11/2) corresponding to the transitions of type 4F9/2 → 6HJ. The strongest emission peak obtained at ∼ 575 nm is responsible for yellow emission of Dy (III) complexes. The yellow to blue (Y/B) ratio estimated for the transition J = 13/2 / J = 15/2 were found to be in the range of 4.19 – 2.80. The quantum yield was also determined for the Dy (III) complexes which is as: Φ1 = 0.315, Φ2 = 0.261, Φ3 = 0.183, Φ4 = 0.157. The synthesized dysprosium complexes demonstrate luminescence lifetime in decreasing order i.e. 0.600 ms > 0.510 ms > 0.431 ms > 0.323 ms. Furthermore, the chromaticity coordinates also confirm their yellow luminous behavior. These newly synthesized complexes could be utilized for developing systems significant for lighting, OLEDs and displays due to their luminous features.

Impact of Anchoring Groups on the Photocatalytic Performance of Iridium(III) Complexes and Their Toxicological Analysis.

Three different iridium(III) complexes, labelled as Ir1-Ir3, each bearing a unique anchoring moiety (diethyl [2,2'-bipyridine]-4,4'-dicarboxylate, tetraethyl [2,2'-bipyridine]-4,4'-diylbis(phosphonate), or [2,2'-biquinoline]-4,4'-dicarboxylic acid), were synthesized to serve as photosensitizers. Their electrochemical and photophysical characteristics were systematically investigated. ERP measurements were employed to elucidate the impact of the anchoring groups on the photocatalytic hydrogen generation performance of the complexes. The novel iridium(III) complexes were integrated with platinized TiO2 (Pt-TiO2) nanoparticles and tested for their ability to catalyze hydrogen production under visible light. A H2 turnover number (TON) of up to 3670 was obtained upon irradiation for 120 h. The complexes with tetraethyl [2,2'-bipyridine]-4,4'-diylbis(phosphonate) anchoring groups were found to outperform those bearing other moieties, which may be one of the important steps in the development of high-efficiency iridium(III) photosensitizers for hydrogen generation by water splitting. Additionally, toxicological analyses found no significant difference in the toxicity to luminescent bacteria of any of the present iridium(III) complexes compared with that of TiO2, which implies that the complexes investigated in this study do not pose a high risk to the aquatic environment compared to TiO2.

Photo-Physical Characteristics of Janus Green B in Different Solvents and its Interaction Mechanism with Silver Nanoparticles.

This work explores the effects of solvent polarity on Janus Green B (JGB) photophysical properties. The Lippert-Mataga, Billot, and Ravi equations were utilized to calculate the singlet-state excited dipole moments (µe) and ground state dipole moments (µg) using absorption and fluorescence spectra analyses. The results showed an increase in the former, which is suggestive of electronic structural alterations upon excitation. Analysis of fluorescence quantum yield values revealed that JGB's environment had an impact on its emission characteristics; it was particularly sensitive to silver nanoparticles, suggesting possible interactions. While simulations of electron density, electrostatic potential, and energy gap (Eg) helped to understand the electronic structure of JGB, theoretical absorption spectra produced by Time Dependent Density Function Theory (TD-DFT) calculations offered insights into electronic transitions during absorption. To sum up, the present study contributes to our comprehension of the molecular behavior of JGB in various solvents by elucidating the intricate relationship among solvent polarity, molecular environment, and interactions with silver nanoparticles. Additionally, theoretical computations support the interpretation of experimental results.

Ultrafast and Quantitative FRET Sensitization of Singlet Fission in Solution‐Processable Para‐Azaquinodimethane Films

AbstractIn this work, a green protocol for the synthesis of new para‐Azaquinodimethane (pAQM) small molecules, functionalized with anisole (An) or bithiophene (TT) moieties on the central unit and with different alkoxy groups as lateral substituents is developed and reported. The alkoxy lateral substituents are found to strongly impact the solubility and processability of the chromophores. On the other hand, the steady–state and time‐resolved spectroscopic results show completely different spectral and photophysical features for the An‐ and TT‐ derivatives. Only for the TT‐compounds, the nanosecond and femtosecond transient absorption experiments reveal low efficiency of triplet production in solution as well as ultrafast (≈1 ps) and efficient (≈200%) singlet fission (SF) in thin film. The yellow An‐containing molecules are instead used to sensitize the purple SF‐active TT‐compounds via quantitative FRET in mixed thin films, which interestingly exhibit panchromatic absorption extending in the entire visible spectral range. With this study, the synergy between FRET and SF is exploited at the intermolecular level in the solid‐state for the first time by considering unconventional and stable SF chromophores, opening intriguing new possibilities for solar energy harvesting.