Absorption Wavelength Research Articles

Complexation of ThoriumIV with Fluorinated Heterocyclic β‐Diketones in Aqueous Hydrochloric Solutions

AbstractThe interaction of Thorium(IV) with a group of non‐symmetric CF3‐diketones has been studied by means of electronic absorption spectroscopy in HCl aqueous solutions at I=0.5 M (NaCl) and T=298 K. Six heterocyclic dicarbonyl ligands (2‐thenoyl‐trifluoroacetone, 2‐furoyl‐trifluoroacetone, 2‐selenophen‐trifluoroacetone, 2‐tellurophen‐trifluoroacetone, phenyl‐trifluoroacetone, and 2‐naphthyl‐trifluoroacetone) demonstrate the chelation activity toward ThIV in the acidic pH range. Obtained values of the “true” stability constants lie in the range 6.2–6.8 logarithmic units, respectively. A significant (10–15 nm) bathochromic shift between the maximum absorption wavelength of lanthanide and actinide monocomplexes has been detected. Observed spectral shift increases with the atomic number of substituted chalcogen atoms in the heterocyclic ring of the corresponding ligand: 10 nm for furan, 11 nm for thiophen, 14 nm for selenophen, and 15 nm for tellurophene rings. The complexation with Thorium occurs in an acidic media, where studied ligands do not interact with transition and rare earth metals. Spectral and pH shifts make studied ligands useful reagents for the detection and analytical determination of Thorium in the mixture with other metals without prior separation. Quantum‐chemical simulations (DFT and TD‐DFT) demonstrate that the nine‐ and deco‐coordinated structures of ThoriumIV complexes reproduce experimental values within reasonable errors.

Effective synthesis of fluorescent carbon dots and their application in controllable detection of deferasirox

As an iron chelation therapy, deferasirox (DEF) is commonly used as the primary treatment drug to prevent intracellular iron overload in patients with thalassemia who require long-term and large blood transfusions. However, due to the toxic side effects of long-term use, building a convenient and sensitive DEF detection method remains an important task. This study developed a simple and effective fluorescence detection strategy for DEF based on the coordination effect of DEF and Cu2+ (DEF-Cu). The high quantum yield N-doped blue emission carbon dots (CDs) synthesized by a simple one-step hydrothermal method were applied as the fluorescent probe. The DEF-Cu exhibited a new absorption peak centered at 334 nm, overlapping with the absorption wavelength of CDs, resulting in an internal filtration effect (IFE) for quenching the fluorescence of CDs. The quenching degrees of CDs caused by DEF-Cu showed a good linear relationship in the range of 0.5–20 μg/mL, with a detection limit (LOD) as low as 0.12 μg/mL. The accurate detections of DEF in dispersible tablets and plasma were also achieved. This strategy not only enriched the understanding of the properties of target drugs but also provided valuable insights for designing CDs with specific luminescent properties and applying them to distinctive methods for drug analysis.

Decomposer faecal food web and C sequestration in soil. Can near infrared spectroscopy describe transfers and transformations from fresh organic inputs to protected forms in soil aggregates?

This study sought to characterize the transfer of agricultural organic inputs by macrofauna to the biogenic aggregate compartments of the soil and test the existence of a faecal food web process based on coprophagic feeding behaviours. In an experimental plantain crop field of Colombia, we applied the agroecological FBO (Fertilisation Bio Organique ®) technology, a nucleation technique which consists in planting perennial plants in 1.0 x 0.4 × 0.4 m deep trenches where low- and high-quality organic materials are added in a specific design, and endogeic earthworms are inoculated. We evaluated the effectiveness of Near Infrared Spectroscopy (NIRS) to track this flow of organic matter through different natural stages of decomposition represented by soil macroaggregates produced by soil macroinvertebrates as faecal pellets and casts. After one year, great part of the organic inputs had been either mineralized or incorporated into macroaggregates of different sizes and origins. Using NIRS and physicochemical laboratory analyses, we assessed the quality and quantity of organic matter in the different types of aggregates separated manually according to their origin: large biogenic aggregates (LBA), medium sized biogenic aggregates (MBA) and small biogenic aggregates (SBA); physical aggregates (PA), root aggregates (RA) and residual soil (RS).Earlier studies had shown that these structures were presumably formed by the activity of macroinvertebrates of three different functional groups, Diplopoda and Isopoda litter transformers for SBA, epidendogeic earthworms for MBA and mesohumic endogeic earthworms for LBA, organized in a feeding succession.A Coinertia analysis between showed significant covariation among the two sets of physico chemical (22 variables) and NIR spectral (100 different wavelength absorbances) characterization of 135 samples representative of the three classes of biogenic macroaggregates, physical aggregates and residual non macroaggregated soil, (RV = 0.55; p < 0.001). This analysis clearly separated biogenic structures and ranked them according to their size, from small SBA to medium sized MBA and large LBA. Physical PA aggregates and RS residual soil were projected close to the LBAs in the coinertia factorial plan. Multiple combinatorial data analysis CDA, associated 5 specific wavelength absorbance ranges with aggregate types and residual soil. Along the sequence from small to large biogenic aggregates, residual soil and physical aggregates, wavelengths associated to easily decomposed substrates (in ranges 1708–1716 nm; 1796–1948 and 2164–2316 nm) had progressively decreasing absorbances. Substrates associated to slowly decomposing aromatic, alkane and phenolic substrates either increased (1420–1436) or decreased (1284–1380) along this sequence.These results are compatible with the hypothesis of a progressive transformation and transfer of organic residues first into small biogenic aggregates that are presumably faecal pellets of Isopoda and Diplopoda, then to medium sized biogenic aggregates identified as casts of epiendogeic earthworms and finally to large biogenic aggregates expected to be the casts of the large endogeic earthworms present in these soils. A definitive verification of the hypothesis and the involvement of specific macroinvertebrates will require direct experimentation in controlled laboratory conditions.

Surface plasmon polariton–enhanced upconversion luminescence for biosensing applications

Abstract Upconversion luminescence (UCL) has great potential for highly sensitive biosensing due to its unique wavelength shift properties. The main limitation of UCL is its low quantum efficiency, which is typically compensated using low-noise detectors and high-intensity excitation. In this work, we demonstrate surface plasmon polariton (SPP)-enhanced UCL for biosensing applications. SPPs are excited by using a gold grating. The gold grating is optimized to match the SPP resonance with the absorption wavelength of upconverting nanoparticles (UCNPs). Functionalized UCNPs conjugated with antibodies are immobilized on the surface of the fabricated gold grating. We achieve an UCL enhancement up to 65 times at low excitation power density. This enhancement results from the increase in the absorption cross section of UCNPs caused by the SPP coupling on the grating surface. Computationally, we investigated a slight quenching effect in the emission process with UCNPs near gold surfaces. The experimental observations were in good agreement with the simulation results. The work enables UCL-based assays with reduced excitation intensity that are needed, for example, in scanning-free imaging.

Room temperature stimulated long-persistent phosphorescence of polyurethane/SrAl2O4: Eu2+, Dy3+ composite material for textile-based applications

Textile-based SrAl2O4(SAO): Eu2+, Dy3+ composite material offers functional, aesthetic, and safety benefits, making it a valuable innovation with diverse applications in various industries. The susceptibility of textile-based SAO: Eu2+, Dy3+ composite material is degraded with repeated washing, which can diminish its luminescent properties over time. Our major goal was to create a cloth with durable photoluminescent qualities by incorporating waterborne polyurethane (WPU) as a protective coating that could generate light constantly without a light source. Through a systematic approach involving the synthesis of photoluminescent SAO: Eu2+, Dy3+ particles and their integration into a cloth substrate with waterborne polyurethane, a durable cloth with enhanced durability, protection, and adhesion properties are achieved. Cotton fabric and a rotary screen-printing machine were used to apply a thin, translucent layer of glow-in-the-dark pigment to produce the photoluminescence characteristics of the developed cloth revealing efficient light absorption and emission behavior, with emission spectra centered around absorption wavelength between 560 nm and 880 nm, with a 500 nm emission peak, exhibiting of the presence of Eu2+ and Dy3+ activator ions. In addition, to assess the comfort of the treated cotton fabric, a fabroOmeter test was conducted, that provided insights into its overall comfort level. Furthermore, the cloth demonstrates excellent stability and longevity of photoluminescence under various environmental conditions, making it suitable for applications requiring high visibility, safety signage, decorative elements, and apparel wear. This research underscores the potential of polyurethane-enhanced photoluminescent textiles as versatile and sustainable solutions for diverse practical applications.

Bicyclic-Ammonium-Incorporated Ylidic Nitrogen Groups for Strong π-Electron Donation in Push-Pull Benzene π-Conjugated Systems.

Ylidic nitrogen-based π-electron-donating groups, (quinuclidinio)amidyl (QA) and (1-azanorbornanio)amidyl (ANA) groups, were developed to shift the absorption of push-pull benzenes toward longer wavelengths. Changing the pyrrolidinyl group to the QA or ANA group achieved a bathochromic shift of 45-100 nm in the maximum absorption wavelength, depending on the push-pull π-conjugated system investigated (p-nitrobenzene, 1,8-naphthalimide, and an azo dye).

Formation mechanism of giant squid myofibrillar protein aggregates induced by egg white protein during heat treatment

In order to solve the problem of poor performance of giant squid gel, this study proposed a method to induce the aggregation of giant squid protein molecules by exogenous additives to improve its gel performance. The particle size, zeta potential, free sulfhydryl group, carbonyl group and hydrophobic index of protein solution were characterized by laser light scattering, fluorescence spectrum and ultraviolet spectrum, and the effect of egg white protein (EWP) on myofibrillar protein (MP) aggregation was analyzed. In the presence of EWP, the density and Rg/Rh value of protein particles decreased significantly after mixing for 600 min, indicating that the interaction between MP and EWP protein could be enhanced by embedding appropriate amount of EWP in the middle of MP protein. With the increase of the proportion of egg white protein, the blue shift of the maximum absorption wavelength of endogenous fluorescence in the mixed protein solution decreased. In the range of 25–65 °C, the change rates of surface charge, free sulfhydryl group, carbonyl group and surface hydrophobicity decreased, which proved that EWP inhibited the self-aggregation rate of MP molecules during the heating process, and induced its gel by interspersing between MP molecules to improve the formation of three-dimensional network during protein thermal gel process. Finally, the addition of EWP improved the gel properties of giant squid surimi. This study offered new direction for improving gel properties and promotes the development and application of giant squid.

Deep near infrared light-excited stable synergistic photodynamic and photothermal therapies based on P-IR890 nano-photosensitizer constructed via a non-cyanine dye

The cyanine dyes represented by IR780 can achieve synergistic photodynamic therapy (PDT) and photothermal therapy (PTT) under the stimulation of near-infrared (NIR) light (commonly 808 nm). Unfortunately, the stability of NIR-excited cyanine dyes is not satisfactory. These cyanine dyes can be attacked by self-generated reactive oxygen species (ROS) during PDT processes, resulting in structural damage and rapid degradation, which is fatal for phototherapy. To address this issue, a novel non-cyanine dye (IR890) was elaborately designed and synthesized by our team. The maximum absorption wavelength of IR890 was located in the deep NIR region (ca. 890 nm), which was beneficial for further improving tissue penetration depth. Importantly, IR890 exhibited good stability when continuously illuminated by deep NIR light. To improve the hydrophilicity and biocompatibility, the hydrophobic IR890 dye was grafted onto the side chain of hydrophilic polymer (POEGMA-b-PGMA-g-CCH) via click chemistry. Then, the synthesized POEGMA-b-PGMA-g-IR890 amphiphilic polymer was utilized to prepare P-IR890 nano-photosensitizer via self-assembly method. Under irradiation with deep NIR light (850 nm, 0.5 W/cm2, 10 min), the dye degradation rate of P-IR890 was less than 5%. However, IR780 was almost completely degraded with the same light output power density and irradiation duration. In addition, P-IR890 could stably generate a large number of ROS and heat at the same time. It was rarely reported that the stable synergistic combination therapy of PDT and PTT could be efficiently performed by a single photosensitizer via irradiation with deep NIR light. P-IR890 exhibited favorable anti-tumor outcomes through apoptosis pathway. Therefore, the P-IR890 could provide a new insight into the design of photosensitizers and new opportunities for synergistic combination therapy of PDT and PTT.

Study of photosensitizer dyes for high-performance dye-sensitized solar cells application: A computational investigation

Dye-sensitized solar cells (DSSCs) offer a promising, cost-effective alternative to conventional photovoltaic systems. Organic sensitizers, capable of capturing a broad spectrum of sunlight, are key components in DSSCs, but their development and testing are often time-consuming and expensive. Quantum chemical calculations, specifically Density Functional Theory (DFT), have emerged as valuable tools to evaluate potential dye candidates, streamlining the design process and reducing costs. This study investigated the molecular structures and photophysical properties of three common dye classes used in high-performance DSSCs: natural pigments, anthocyanidin pigments, and squaraine dyes. Employing DFT and time-dependent DFT (TD-DFT) at the B3LYP/6–31G level, key parameters such as the HOMO-LUMO energy gap, free energy differences for electron injection and dye regeneration, short-circuit current density, total reorganization energy, and open-circuit voltage were analyzed. Additionally, maximum absorption wavelengths and oscillator strength values were calculated. Our findings provide valuable insights into the optical and electrical properties of these natural dyes, aiding DSSC manufacturers in selecting optimal sensitizers. This research highlights the potential of computational methods in accelerating dye development and improving the overall efficiency of DSSC technology.

In-silico optimization of resveratrol interaction with nano-borophene: A DFT-guided study of supramolecular artistry

In this study, the potential of borophene (BOR) as a drug delivery system for resveratrol (RVT) was explored to evaluate its efficacy in cancer treatment. The excited, electronic, and geometric states of RVT, BOR, and the borophene-adsorbed resveratrol complex (BOR@RVT) were calculated to assess BOR's suitability as a drug carrier. Noncovalent interaction (NCI) plots indicated a weak force of attraction between BOR and RVT, which facilitates the offloading of RVT at the target site. Frontier molecular orbital (FMO) analysis showed that during electron excitation from Highest Occupied Molecular Orbital (HOMO) to Lowest Unoccupied Molecular Orbital (LUMO), charge transfer occurs from RVT to BOR. This was further confirmed by charge decomposition analysis (CDA). Calculations for the excited state of BOR@RVT revealed a red shift in the maximum absorption wavelength (λmax), indicating a photoinduced electron transfer (PET) process across various excited states. PET analysis demonstrated fluorescence quenching due to this interaction. Our findings suggest that BOR holds significant potential as a drug delivery vehicle for cancer treatment, offering a promising platform for the development of advanced drug delivery systems.

Phenolic profiles of Australian monofloral Eucalyptus, Corymbia, Macadamia and Lophostemon honeys via HPLC-DAD analysis

Australian honey samples from four botanical genera (Lophostemon, Eucalyptus, Macadamia and Corymbia) were investigated for their phenolic content. An improved phenolic extraction and high-performance liquid chromatography-diode array detection (HPLC-DAD) analysis method allowed for the rapid and reliable identification of phenolic compounds. A concentrated liquid-liquid extraction method with an acidified aqueous solution and acetonitrile was optimised to isolate phenolic compounds from the honey matrix. The concentrated extraction method improved sensitivity and permitted the identification of phenolics present at low concentrations (LOD: 0.012–0.25 mg/kg and LOQ: 0.040–2.99 mg/kg). The optimised HPLC-DAD chromatographic conditions gave stable retention times, improved peak separation and allowed for the inexpensive detection of each of the 109 phenolic compounds at their maximum absorbance wavelength. Out of the 109 phenolic compounds included in this study, 49 were identified in the Australian honeys tested. Furthermore, 25 of the 49 compounds were determined to be markers specific to honey floral origin.

Structural, electronic, and NLO properties of two acridone alkaloîds: DFT and TD-DFT studies.

The structural, electronic, and nonlinear optical properties of Verdoocridone A (Ver A) and B (Ver B) are examined theoretically in this study. The results showed that Ver A and B exhibit good electronic properties and can be used as new materials in NLO applications. According to their maximum absorption wavelength, Ver A (λmax = 313nm) enables production of vitamin D, while Ver B (λmax = 319.55nm) can help skin pigmentation. All calculations were performed at the DFT/B3LYP-D3/6-311 + G(d,p) level of theory using the Gaussian 16 software package. Excited states were simulated using the TD-DFT method at the CAM-B3LYP combined with 6-311 + (d,p) basis set. Also, the solvent effect was studied in water and benzene phases by the solvation model based on density (SMD) method.

Exploring solvatochromism: a comprehensive analysis of research data of the solvent -solute interactions of 4-nitro-2-cyano-azo benzene-meta toluidine

This study investigates the solvatochromic behavior of a new D1 disperse dye, focusing on the 4-nitro-2-cyano-azo-Benzene-metaToluidine type. Using UV-visible spectroscopy, we analyze the dye’s performance in single solvents and binary mixtures. Our analysis includes the evaluation of solvent polarity parameters and dye structure parameters, with emphasis on the longest wavelength intramolecular charge transfer absorption band. We identify nonlinear and linear patterns in the electronic transition energies plots with respect to solvent composition. Statistical analysis considers correlation coefficients, root mean squared error, mean absolute percentage error, and other parameters, providing insights into data accuracy and precision. This experimental and statistical study explores the absorption spectrum, wavelength characteristics, absorption energy, and polarity of a novel azo dye across various solvent and solute environments. These findings contribute to a comprehensive understanding of the dye’s photophysical and photochemical properties, potentially enabling applications in optical sensors and advanced materials.Graphical abstract

Achieving ultrahigh electrochromic stability of triarylamine-based polymers by the design of five electroactive nitrogen centers

A shortage of long-term stability of electrochromic materials has been hindering their practical application. A series of novel polyamides (PAs) (4) with five electroactive nitrogen atoms within triphenylamine (TPA)-containing structures was synthesized via phosphorylation polyamidation. Polyamide 4b exhibited highly integrated electrochromic performances, including multiple color changes, high contrast of optical transmittance change, and the highest electrochromic stability (only 11.2 and 9.6 % decay of its coloration efficiency (CE) at 450 nm after 50000 and 16000 switching cycles, respectively) compared to all other triarylamine-based polymers to date. This record-high electrochromic cycling is attributed to the enhanced stability of polaron, which was studied through the electron-donating or electron-withdrawing effect of substituents and the resonance effect of electron delocalization over the electroactive nitrogen centers. Importantly, our core design of five electroactive nitrogen centers with electron-donating methoxy groups is the key factor to increase stability of polaron in the resulting polymers 4. More electroactive nitrogen centers are able to create a weaker electronic coupling due to a charge of cation radical dispersed by resonance successfully in-between the different redox states, which is evidenced clearly by the observed longer wavelength absorption in the NIR region. Our research confirms that the key to determining polaron stability is the resonance by the electrons delocalized over all the redox centers, rather than the electronic coupling between the different redox centers. And the resonance leads to increasing electrochromic stability of the polymer.

Synthesis and evaluation of 5,15-diaryltetrabenzoporphyrins as photosensitizers for photo-diagnosis and photodynamic activity of tumors

Photodynamic therapy (PDT) is a well-established treatment modality, typically conducted with single-wavelength irradiation, which may not always be optimal for varying tumor locations and sizes. To address this, photosensitizers with absorption wavelengths ranging from 550 to 760 nm are being explored. Herein, a series of 5,15-diaryltetrabenzoporphyrins (Ar2TBPs) were synthesized. All compounds displayed obvious absorption at 550–700 nm (especially at ∼668 nm), intense fluorescence, efficient generation of singlet oxygen and good photodynamic antitumor effects. Notably, compound I3 (5,15-bis[(4-carboxymethoxy)phenyl]tetrabenzoporphyrin) showed excellent cytotoxicity against Eca-109 cell line upon red light irradiation, with an IC50 value of 0.45 μM, and phototherapeutic index of 25.8. Flow cytometry revealed that I3 could induce distinct cell apoptosis. In vivo studies revealed that compound I3 selectively accumulated at tumor site and exhibited outstanding PDT effect with antitumor activity under single-time administration and light irradiation, and revealed more efficiency than the clinical photosensitizer Verteporfin. These findings underscore the considerable promise of I3 as a robust theranostic agent, offering capabilities in real-time fluorescence imaging and serving as a potent photosensitizer for personalized and precise photodynamic therapy of tumors.

Computational Assessment of Novel Ruthenium Phenoxazine‐Based Complexes as Photosensitizers in Photodynamic Therapy

A computational examination of two new polypyridyl ruthenium complexes, containing meldola blue (MDB) and nile blue (NB) chromophores, is here reported in order to assess the applicability of phenoxazine‐containing complexes in photodynamic therapy (PDT). The designed complexes, named Ru‐3ENB and Ru‐3EMDB, are based on a recently synthesized Ru(II)‐based complex bearing a bipyridyl‐ethynyl‐Nile Red (NR) ligand and proposed for PDT applications. DFT outcomes elucidated how the replacement of NR with MDB induces a red shift of the maximum absorption wavelength within the therapeutic window, up to 638 nm. A change in the molecular orbitals involved in the population of excited states was observed upon chromophore substitution that results in ISC kinetic significantly faster than that computed for the synthesized complex Ru‐3ENR.

A highly sensitive colorimetric and fluorometric sensor for the detection of cyanide

Certain anions play a vital role in metabolic reactions in our body, but the cyanide ion is highly toxic and poisonous to humans, animals, and the environment even at extremely low concentrations. To detect CN−ions, a highly sensitive electron donor-π-acceptor molecular system (IC) was designed based on the carbazole electron donor and 1,3-indanedione electron acceptor. The IC molecular probe was synthesized through simple organic transformations with good yields and characterized by all spectroscopic methods, including single-crystal X-ray diffraction. The IC probe molecule absorbs in the UV–visible region (200–550 nm), and fluorescence emission encompasses 400–750 nm with LE and CT emission bands. A systematic study suggests that the addition of cyanide ions caused both longer wavelength absorption bands and CT fluorescence emission intensity to decrease. Cyanide ion detection can be visualized with the naked eye, where the yellow color of the IC probe solution changes to colorless upon adding cyanide ion solution. Both UV–visible and fluorescence emission spectral changes with the addition of cyanide ions are attributed to the nucleophilic addition of cyanide at the vinylic carbon, which is confirmed by the 1H NMR, HRMS and fluorescence lifetime studies. The cyanide ion detection limit of the IC has been estimated to be 0.43 µM, far below the WHO permissible limit for cyanide ion concentration in potable water, thus broadening the utility of the IC probe in detecting cyanide in Tapioca. A prototype TLC testing strip has been fabricated for the qualitative determination of cyanide in THF/water medium.

Q-factor and wavelength adjustable ultra-perfect absorption under critical coupling through epsilon-near-zero-based absorbers

Perfect absorption with adjustable Q factor and wavelength is essential in both theory and application. To address this issue, a structure composed of an epsilon-near-zero (ENZ)- SiO2 grating and a multilayer dielectric structure was designed. In the structure, the intrinsic loss is related to the ENZ thickness, while the external leakage depends on the grating parameters. By adjusting the ENZ film thickness, the intrinsic loss rate was tuned to match the external leakage rate corresponding to different grating parameters, realizing the critical couplings with different Q factors and wavelengths. Under critical coupling, the absorption rate reached a maximum of 99.999%, demonstrating ultra-perfect absorption. The Q factor was adjusted from 4350 to 35800, and the absorption wavelength was modified from 1050 to 1282 nm. The design work may provide new ideas for developing wavelength- and Q-selective absorbers, optical modulators, dielectric sensors, and photodetectors.

(Invited) In Situ and Operando Scattering Studies on Quantum Dot-Based Devices

Colloidal quantum dots (QDs) made e.g. of PbS are attractive for various optoelectronic applications due to their tunable band gap with a large absorption wavelength range from the visible to the near-infrared region. Moreover, due to the high intrinsic permittivity, the exciton binding energy of PbS is smaller than in cadmium chalcogenide QDs and polymer materials, which is beneficial for devices driven by charge carrier generation and transport, e.g. photovoltaics and photodetectors.In this work, we introduce wet chemical deposition methods beyond spin coating such as printing and spray deposition of QDs as a facile and potentially large-scale deposition method for high-performance photodetectors. The inner structures including the inter-dot distance of neighboring QDs and the structure, in the deposited QD solids, are studied by grazing-incidence small-angle X-ray scattering (GISAXS). In addition, the facet orientation of the QDs in the QD solids is characterized by grazing-incidence wide-angle X-ray scattering (GIWAXS). In particular, in situ GISAXS/GIWAXS studies during film formation are able to provide detailed information about the complex kinetic processes [1,2]. Operando GISAXS/GIWAXS studies on QD-based devices such as solar cells bring an in-depth understanding of the degradation mechanisms, which is key for improving the device stability and thereby bringing these novel materials into real-world applications [3]. Superlattice deformation in QD films on flexible substrates via uniaxial strain is followed in situ with GISAXS, providing a fundamental understanding of the impact of strain on the performance of flexible devices based on QD films, such as wearable electronics and next-generation solar cells on flexible substrates [4]. Nanoscale Horiz. 5, 880-885 (2020)Nano Energy 78, 105254 (2020)Energy Environ. Sci. 14, 3420-3429 (2021)Mater. Horizon 8, 383-395 (2023)

Pressure-Induced Enhancement of Room-Temperature Phosphorescence in Heavy Halogen-Containing Imide and Polyimide.

To investigate the correlation between the aggregated state and photoluminescence (PL) mechanism of dual fluorescent (FL) and phosphorescent (PH) polyimides (PIs), the photophysical processes of FL-type BP-PI, PH-type DBrBP-PI, and their corresponding imide model compounds (BP-MC and DBrBP-MC) dispersed in poly(methyl methacrylate) (PMMA) films were analyzed at elevated pressures up to 8 GPa using a diamond anvil cell. Dibromo-substituted DBrBP-MC demonstrated a shorter wavelength absorption than BP-MC owing to the larger dihedral angle in the biphenyl moiety. Both MCs exhibited red-shifts in their absorption spectra with increasing pressure, indicating planarization occurred at the biphenyl moieties associated with the compression of the free volume in PMMA. The PL intensity of BP-MC increased with increasing pressure, while its quantum yield (ΦPL) decreased sharply due to the enhanced energy transfer via the Förster mechanism. In contrast, the PH quantum yield (ΦPH) of DBrBP-MC monotonically increased at lower pressures, while it showed excitation wavelength-dependent behaviors at higher pressures: ΦPH remained unchanged under excitation at 340 nm but gradually increased under excitation at 365 nm. This fact suggests that, at higher pressures, 365 nm excitation promoted intersystem crossing (ISC) from excited singlet states at higher energy levels. Using this phenomenon, a significant pressure-induced PH enhancement (PIPE) was observed for DBrBP-PI up to 0.9 GPa upon excitation at 365 nm, which is a rare phenomenon for organic polymers. This study indicates that even in colorless and optically transparent amorphous polymers, an enhancement of PH due to restricted molecular motion and intensified ISC outweighs the deactivation due to intermolecular energy transfer under certain pressures, leading to an increase in ΦPH.