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This study presents the fabrication and characterization of TiO2 nanorods (NRs) synthesized via the hydrothermal method, employing different precursor concentrations and hydrothermal durations. Comprehensive analyses of surface morphology, crystal structure, and optical properties were conducted using scanning electron microscopy (SEM), x-ray diffraction (XRD), ultraviolet–visible (UV–Vis) spectroscopy, and photoluminescence (PL) spectroscopy. XRD patterns and transmittance spectra confirmed that the TiO2 NRs possess a single-phase rutile structure with a band gap of approximately 3.11 eV. Notably, the PL quenching coefficient reached 93%, indicating excellent carrier transport efficiency between halide perovskite materials and TiO2 NRs. These findings highlight the potential of TiO2 NRs as efficient electronic transport layers in high-performance optoelectronic devices, such as perovskite solar cells. [ABSTRACT FROM AUTHOR]

Functionalized carbon quantum dots with tunable optical properties widely used in sensor applications. In this study, carbon quantum dots were synthesized from Zelkova serrata leaves (ZCQDs) in an aqueous medium via a single-step hydrothermal reaction with essential reactive functional groups. As-synthesized ZCQDs (average size, 3–7 nm) were characterized and confirmed to contain hydroxyl/amine and carboxylic acid functional groups. Photoluminescence spectral analysis revealed that the fluorescence intensity of ZCQDs drastically decreased after the addition of different concentrations of normetanephrine (NM) in deionized water and geriatric plasma samples. Our developed strategy could detect NM with a limit of detection of 7.96 and 86.2 nM in deionized water and geriatric plasma samples, respectively. Interestingly, Fourier transform infrared spectroscopy revealed a new peak at 1660 cm−1, confirming the formation of the keto (C=O) group in NM. In addition, significant peak shifts were observed in the C 1s, and O 1s deconvoluted X-ray photoelectron spectra. Bandgap calculations also revealed significant interactions between NM and ZCQDs. Antibacterial activities of ZCQDs were investigated in Escherichia coli and Staphylococcus aureus, and potent activities were observed in Staphylococcus aureus at a half-maximal inhibitory concentration of 32 μg/mL via the generation of intracellular reactive oxygen species. By enabling specific therapies and improving our understanding of intricate biological processes at the nanoscale, these materials have the potential to completely transform the biomedical field. Our findings suggest the involvement of a working mechanism in transferring electrons between the conductance band of ZCQDs and the acidic protons of N, to produce the oxidized form NM for photoluminescence quenching of ZCQDs. [ABSTRACT FROM AUTHOR]

Combination of affordable organic dyes of high quantum yield with silicon can be an interesting way for development of highly efficient thin film photovoltaic cells utilizing silicon sensitisation. This work is focused on investigating the energy transfer processes including photon tunnelling from photosensitive molecules of BASF R305 high quantum yield dye to silicon substrate. Energy transfer from dye molecules to silicon substrate is evaluated by measuring the quenching of molecular photoluminescence lifetime using time-correlated single photon counting (TCSPC) technique. Energy transfer is further studied in dependence on dye layer thickness. The results can be useful for further studies leading to design of ultrathin silicon solar cells. [ABSTRACT FROM AUTHOR]

Two Al-MOFs, i.e., MIL-53 (Al) and (NH2)-MIL-53 (Al) have been synthesized using aluminium nitrate as metal ligands and 1,4 benzene dicarboxylic acid, amino 1,4 benzene dicarboxylic acid as organic linkers in aqueous medium at room temperature, respectively. Both Al-MOFs have been confirmed through different microscopy and spectroscopy tools. Afterwards, the optical properties of Al-MOFs have been confirmed in polar and non-polar solvents using photoluminescence spectroscopy. Finally, both Al-MOFs have been explored for optical nitrobenzene (NB) sensing. Interestingly, we have found excellent optical ability of NH2-MIL-53 (Al) over MIL-53 (Al) due to structural π–π* transitions. The photo-induced electron transfer mechanism has been found during the MOF–analyte interaction. Importantly, we confirmed that NH2-MIL-53 (Al) is an excellent sensing material for NB with a 0.28 ppb limit of detection over MIL-53 (Al). [ABSTRACT FROM AUTHOR]

The charge transfer study from the excited state of MAPbBr3 perovskite nanocrystals (PNCs) to molybdenum disulfide (MoS2) in chloroform solution is conducted using a fluorescence approach. Due to their exceptional properties and distinctive structures, transition metal dichalcogenides (TMDs) are promising candidates for optoelectronic devices. In this study, we have combined hybrid organic–inorganic perovskite nanocrystals MAPbBr3 with MoS2 solution. A significant electron transfer from MAPbBr3 to MoS2 has been depicted by photoluminescence (PL) spectroscopy, time-correlated single-photon count (TCSPC), transient absorption spectroscopy (TAS), and shortening of the absolute PL quantum yield (PLQY) of hybrid MAPbBr3/MoS2 nanocomposites. Fluorescence quenching of perovskite nanocrystals has shown an increase in quenching efficiency. The photoexcited charge transfer from MAPbBr3 to adjacent MoS2 is further correlated using electrochemical tests that compare reduction and oxidation potential. The results revealed that MoS2 extracts the charge from the excited state of PNCs. This work demonstrates the charge transfer properties of hybrid halide perovskites with two-dimensional TMD materials. A combination of these materials could help us to understand the actual potency of MAPbBr3 PNCs in their real applications. [ABSTRACT FROM AUTHOR]

Experimental temperature dependences (77–293 K) of absorption and photoluminescence spectra of CdSe/ZnS semiconductor quantum dots (QDs) were analyzed based on modern models of exciton–phonon coupling. It was proven that the first excitonic transition absorption band formed with participation primarily of optical phonons of the CdSe core while the photoluminescence properties reflected the interaction of the ZnS layer with optical phonons. Photoluminescence quenching for CdSe/ZnS QDs of various diameters upon formation of nanoassemblies with porphyrin molecules was analyzed in the framework of a quantum-mechanical model. It was shown that the quenching rate constant decreased with increasing QD diameter and that the quenching process under quantum confinement conditions was due to the electron of an excited electron–hole pair tunneling onto the QD surface with subsequent localization on surface traps. [ABSTRACT FROM AUTHOR]

The results of studies on the optical properties of colloidal InP/ZnS nanocrystals stabilized by a heterobifunctional polymer based on polyvinylpyrrolidone are presented. The optical absorption and photoluminescence spectra of (i) solutions containing different concentrations of nanocrystals and (ii) film samples, as well as the temperature dependences of these spectra in the range of 6.5–296 K are analyzed. An inhomogeneous broadening of the exciton optical bands was observed, which is associated with a broad size distribution of nanocrystals. It was established that the temperature-induced shift of the exciton absorption and emission maxima is mainly due to the interaction with acoustic phonons. It was shown that quenching of defect-related luminescence involves the local energy levels of the dangling bonds of phosphorus atoms at the core—shell interface, while the temperature stability of exciton emission is governed by the thickness of the ZnS shell. [ABSTRACT FROM AUTHOR]

Photoinduced charge transfer (CT) is decisive to the efficiency and speed of photoelectric conversion in two-dimensional (2D) van der Waals (vdWs) heterostructures. Generally, CT rate enhancement is realized by increasing the band offset (BO). In this study, we propose that a fast and efficient CT can be realized via strong hybridization of energy levels in 2D vdWs heterostructures with minimal BO. First-principles calculations reveal that the smallest energy difference between conduction-band edges and minimal BO in the WS2/WxMo1−xS2 (x = 0.78) heterostructure yields the strong hybridization of energy levels and then results in ultrafast CT (2.7 ps). Experimental results agree with theoretical calculations. The photoluminescence of WS2 is quenched in the WS2/WxMo1−xS2 (x = 0.78) heterostructure, attributable to the strong hybridization-induced fast and efficient CT. This study provides insights into the mechanism of CT in heterostructures and offers new strategies to create superior optoelectronic devices with fast and efficient photoelectric conversion. [ABSTRACT FROM AUTHOR]

Piezophotonics is a great interesting field of physics that has led to a number of important technologies, such as light source, smart sensors, and mechatronics. In this work, we reported Pr-doped (Bi0·5Na0.5)TiO3-based lead-free ceramics with strong red photoluminescence emission and large strain response (d33∗ = 460 pm/V, S = 0.32 %). The PL emission can be quenched by decreasing the intensity by 93 % after electrical polarization (E = 50 kV/cm). The local structure and electric field-induced structural changes were systematically investigated to reveal the significant distinction in photoluminescence properties caused by electrical polarization. The results indicated that polarization treatment eliminates the structural inhomogeneities and establishes a long-range ferroelectric tetragonal and rhombohedral distortion. The crystal structure transformed irreversibly from a non-ergodic to a normal ferroelectric state. PL quenching originated from the decreased distortion of octahedral due to the transition from a non-ergodic state to a highly ordered symmetrical structure. Meanwhile, the enlarged domain structure contributed to the photoluminescence quenching effect. Our findings demonstrate that an electric field can be a robust tool for adjusting the photoluminescence property and provide insights into the relationship between the structure and PL properties of BNT-based ceramics under an external stimulus.

[Display omitted] • Doping of SDS in NLC leads to increased dielectric anisotropy with red-shift • The diffusion coefficient decreases by 80.77 % when the concentration of anionic surfactant increases from 0 to 3.0 wt%. • LC cells with 3.0 wt% anionic surfactant show 30 % decrease in rotational viscosity and 64 % decrease in response time. • A bathochromic shift of 31 nm in UV–Vis spectrum and PL quenching of 64 % is observed with 3.0 wt% dispersion of SDS. Modern research has long focused on controlling and optimizing the dielectric, electro-optical and optical attributes of liquid crystals (LCs) to increase their technological value. Numerous approaches have been investigated for this reason in an effort to overcome various issues such as high response time, high driving voltage requirements, low dielectric anisotropy and limited operating temperature range, etc. The strategy utilizing binary/multicomponent systems is the most investigated and seems to have the most potential out of all the other techniques. In keeping with the same subject, the influence of anionic surfactant on the dielectric, electro-optical, and optical properties of nematic LC (NLC) has been examined. Precisely, dodecane-1-sulfonic acid sodium salt (SDS) which is an anionic surfactant was dispersed in a room temperature NLC E7 at various concentrations. Our findings reveal a significant alteration in the electro-optical behavior resulting from the introduction of an anionic surfactant, extending well beyond the instance of electrode polarization, albeit with a detrimental impact on performance within the low-frequency range as a result of increased ionic contribution. The main findings of this study include a 17.5%% increase in dielectric anisotropy, an appreciable reduction of about 30%% in threshold voltage and rotational viscosity, and approximately 64% reduction in response time in the host NLC due to the addition of anionic salt in it. A significant photoluminescence quenching of about 64%% is observed after dispersion of 3.0% by weight anionic surfactant in E7. These findings offer potential pathways for the development of future technologies in various domains, including photonic devices, biological imaging, light-emitting diodes (LEDs), and luminescent markers. [ABSTRACT FROM AUTHOR]

Heterostructure is the basic building block for functional optoelectronic devices. Heterostructures consisting of two-dimensional (2D) transition metal dichalcogenides (TMDs) and organic semiconductors are currently attracting great interest for high-performance optoelectronics. However, how to design heterostructure for highly efficient optoelectronic devices remains a big challenge. Here we design high-performance organic semiconductor/WSe2 heterostructure photodetectors by tailoring the charge transfer effect between 2,2′-((2Z,2′Z)-(((4,4,9,9-tetrakis(4-hexylphenyl)-4,9- dihydros-indaceno[1,2-b:5,6-b′]dithiophene-2,7-diyl)bis(4-((2-ethylhexyl)oxy)thiophene-5,2-diyl))bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)) dimalononitrile (IEICO-4F) organic semiconductors with various thicknesses and monolayer WSe2. With the increase of IEICO-4F layer thickness, the photoluminescence (PL) characteristics of WSe2 could be completely quenched due to the charge transfer from the lowest unoccupied molecular orbital (LUMO) level of IEICO-4F to the conduction band minimum (CBM) of WSe2. Benefiting from the exquisite charge transfer behavior, the IEICO-4F/WSe2 heterojunction photodetector with optimized 6.0-nm thick IEICO-4F shows high performance including the responsivity of 8.32 A/W and specific detectivity of 4.65 × 1011 Jones at incident light of 808 nm. This work demonstrates a simple approach based on PL characteristics to design high-performance IEICO-4F/WSe2 heterojunction, thus paving the way for the development of excellent optoelectronic devices based on organic/TMD heterostructures. [ABSTRACT FROM AUTHOR]

The correct determination of the exciton diffusion length (LD) in novel organic photovoltaics (OPV) materials is an important, albeit challenging, task required to understand these systems. Herein, a high‐throughput approach to probe LD in nonfullerene acceptors (NFAs) is reported, that builds upon the conventional photoluminescence (PL) surface quenching method using NFA layers with a graded thickness variation in combination with spectroscopic PL mapping. The method is explored for two archetypal NFAs, namely, ITIC and IT‐4F, using PEDOT:PSS and the donor polymer PM6 as two distinct and practically relevant quencher materials. Interestingly, conventional analysis of quenching efficiency as a function of acceptor layer thickness results in a threefold difference in LD values depending on the specific quencher. This discrepancy can be reconciled by accounting for the differences in light in‐ and outcoupling efficiency for different multilayer architectures. In particular, it is shown that the analysis of glass/acceptor/PM6 structures results in a major overestimation of LD, whereas glass/acceptor/PEDOT:PSS structures give no significant contribution to outcoupling, yielding LD values of 6−12 and 8−18 nm for ITIC and IT‐4F, respectively. Hence, practical guidelines for quencher choice, sample geometries, and analysis approach for the accurate assessment of LD are provided. [ABSTRACT FROM AUTHOR]

Nonfullerene organic photovoltaics (OPVs) with small energetic offset between donor and acceptor can provide a much‐reduced voltage loss and power conversion efficiencies over 18%, challenging the previous understanding of the charge generation mechanisms. Herein, a study is presented on nonfullerene OPVs with negative energetic offsets, by investigating a model system which exhibits poor photoluminescence quenching (PLQ, ≈17%) yet reasonably high external quantum efficiency (EQE, ≈50%). It is found that the discrepancy between the poor PLQ and relatively high EQE is dependent on the measurement conditions, namely, short or open circuit, under which the devices exhibit differences in charge generation. Transient absorption spectroscopy shows surprisingly slow hole transfer on nanosecond timescale. It is revealed that the poor PLQ/high radiative recombination originates from an increased back transfer from free carriers to the singlet excitons under open circuit. It is made possible by the slow charge‐transfer (CT) kinetics, long‐lived CT states, and emissive excitons. Despite the negative offset, the charge generation can be relatively efficient under short circuit. The results suggest that the PLQ under open circuit is not necessarily a good indicator of charge separation efficiency and provide new insight to efficient charge generation of OPVs with unfavorable energy offsets. [ABSTRACT FROM AUTHOR]

Monitoring the blood concentration of banoxantrone (AQ4N) is important to evaluate the therapeutic efficacy and side effects of this new anticancer prodrug during its clinical applications. Herein, we report a fluorescence method for AQ4N detection through the modulation of the molecule-like photoinduced electron transfer (PET) behavior of gold nanoclusters (AuNCs). AQ4N can electrostatically bind to the surface of carboxylated chitosan (CC) and dithiothreitol (DTT) co-stabilized AuNCs and quench their fluorescence via a Coulomb interaction-accelerated PET process. Under optimized experimental conditions, the linear range of AQ4N is from 25 to 200 nM and the limit of detection is as low as 5 nM. In addition, this assay is confirmed to be reliable based on its successful use in AQ4N determination in mouse plasma samples. This work offers an effective strategy for AQ4N sensing based on fluorescent AuNCs and widens the application of AuNCs in clinical diagnosis and pharmaceutical analysis. [ABSTRACT FROM AUTHOR]

Diabetes mellitus affects a significant percentage of the world's population, and the incidence of this disease is expected to increase exponentially in the coming years. The development of practical and low-cost glucose sensors is of utmost importance to monitor and manage diabetes and diabetes associated complications. In this scope, a nonenzymatic glucose sensor was produced by growing zinc oxide (ZnO) nanorods on a cellulose-based substrate by microwave-assisted hydrothermal synthesis. The developed sensor relies on ZnO nanorods' photocatalytic ability to photo-oxidize glucose, eliminating the need to use an oxidase enzyme. The quantification of glucose is based on the quenching of the ZnO's photoluminescence signal by the hydrogen peroxide produced during the nonenzymatic oxidation of this monosaccharide. The developed sensor possesses a sensitivity of 1.46%/mM, a linear range between 0.5 and 30 mM, and a limit of detection of 0.103 mM. The sensor showed good selectivity for glucose, and it was also demonstrated that there was a high correlation between the glucose concentration values obtained using the sensor's calibration curve and the clinical data of human plasma samples, therefore validating the use of ZnO nanorods to monitor the glucose concentration in human plasma samples. This work reports for the first time a ZnO-based eco-friendly, stable, and highly selective alternative for glucose monitoring, pointing to a promising future for metal oxide nanostructures for biomedical sensors. [ABSTRACT FROM AUTHOR]

Zinc(II) 2 D polymer, [Zn(3,5-Pydc)0.5·H2O]n (1) {3,5-Pydc = pyridine-3,5-dicarboxylate anion}, has been prepared under sonication conditions. The natural bond orbital (NBO) analysis revealed that charge transfer transitions in the vicinity of Zn(II) is accompanied with the highest stabilization energy of 140.13 kcal/mol. Furthermore, molecular electrostatic potential (MEP) analysis has been carried out to identify the reactive sites over the surface of the complex. 1 was characterized by elemental analysis, FTIR spectroscopy, thermal analysis and single crystal X-ray diffraction. The metal-based luminescence properties revealed that 1 can be used as selective chemosensor against 4-nitroaniline. Complex 1 showed excellent quenching efficiency of 98.9% with KSV value of 3.7 × 105 M−1. Density functional theory simulations complement to the specific luminescence quenching of 1 against 4-nitroaniline. [ABSTRACT FROM AUTHOR]

The time evolution of the photoluminescence properties in phenylethylammonium tin halide perovskite (PEA2SnI4) film as a function of oxygen concentration is reported. Photo‐brightening and reversible photoluminescence quenching are observed in PEA2SnI4 film at ultralow oxygen concentration (< 1.5 vol%). In the case of 1.5 vol% < [O2] < 21 vol%, the photoluminescence emission of PEA2SnI4 film can be partially recovered after resetting the samples to nitrogen box. As the oxygen concentration further increases with the range of 21 to 95 vol%, the photoluminescence emission of PEA2SnI4 film is significantly quenched and can only be slightly recovered after removing it to the nitrogen box. By correlating the material characterizations and theoretical analysis, the interactions between PEA2SnI4 and oxygen contain physisorption and chemical reactions are illustrated. Depending on the oxygen concentration, the chemical reactions between PEA2SnI4 and oxygen can be reversible and/or irreversible. The insights into oxygen concentration effects provide a guideline to optimize the stability of PEA2SnI4 for achieving high‐performance optoelectronic devices. [ABSTRACT FROM AUTHOR]

The development of tin-lead alloyed halide perovskite nanocrystals (PNCs) is highly desirable for creating ultrastable, eco-friendly optoelectronic applications. However, the current incorporation of tin into the lead matrix results in severe photoluminescence (PL) quenching. To date, the precise atomic-scale structural origins of this quenching are still unknown, representing a significant barrier to fully realizing the potential of these materials. Here, we uncover the distinctive defect-related microstructures responsible for PL quenching using atomic-resolution scanning transmission electron microscopy and theoretical calculations. Our findings reveal an increase in point defects and Ruddlesden-Popper (RP) planar faults with increasing tin content. Notably, the point defects include a spectrum of vacancies and previously overlooked antisite defects with bromide vacancies and cation antisite defects emerging as the primary contributors to deep-level defects. Furthermore, the RP planar faults exhibit not only the typical rock-salt stacking pattern found in pure Pb-based PNCs but also previously undocumented microstructures rich in bromide vacancies and deep-level cation antisite defects. Direct strain imaging uncovers severe lattice distortion and significant inhomogeneous strain distributions caused by point defect aggregation, potentially breaking the local force balance and driving RP planar fault formation via lattice slippage. Our work illuminates the nature and evolution of defects in tin-lead alloyed halide perovskite nanocrystals and their profound impact on PL quenching, providing insights that support future material strategies in the development of less toxic tin-lead alloyed perovskite nanocrystals.

van der Waals (vdW) heterostructures composed of multiple vertical stacks of two-dimensional materials exhibit unique optoelectronic properties compared with their single constituent counterparts. The interlayer coupling between adjacent layers directly affects the transfer of excitons and charges, thereby governing the device performance. Herein, we report that the interlayer energy transfer occurring in a transition-metal dichalcogenide/graphene vdW heterostructure strongly depends on the interlayer distance and modulates photocurrent generation. MoSe2/graphene and MoSe2/hexagonal boron nitride (h-BN)/graphene heterostructures comprising chemical-vapor-deposition-grown layers show different degrees of photoluminescence (PL) quenching of MoSe2 with respect to the number of layers and the types of adjacent layers. Comparisons of the Raman and PL spectra revealed that the h-BN interlayer can modulate the long-range exciton energy transfer from MoSe2 to graphene, as corroborated by the photocurrent measurements from the photoconductor devices. These results underscore the effect of modulating the interlayer coupling in vdW heterostructures on the fabrication and control of optoelectronic devices. [ABSTRACT FROM AUTHOR]

The efficiency of bulk heterojunction (BHJ) based organic solar cells is highly dependent on the morphology of the blend film, which is a result of a fine interplay between donor, acceptor, and solvent during the film drying. In this work, a versatile set‐up of in situ spectroscopies is used to follow the morphology evolution during blade coating of three iconic BHJ systems, including polymer:fullerene, polymer:nonfullerene small molecule, and polymer:polymer. the drying and photoluminescence quenching dynamics are systematically study during the film formation of both pristine and BHJ films, which indicate that the component with higher molecular weight dominates the blend film formation and the final morphology. Furthermore, Time‐resolved photoluminescence, which is employed for the first time as an in situ method for such drying studies, allows to quantitatively determine the extent of dynamic and static quenching, as well as the relative change of quantum yield during film formation. This work contributes to a fundamental understanding of microstructure formation during the processing of different blend films. The presented setup is considered to be an important tool for the future development of blend inks for solution‐cast organic or hybrid electronics. [ABSTRACT FROM AUTHOR]

[Display omitted] • N-doped Cdots synthesized by conjugation of 1,4 butanediol L-arginine. • Self-assembly of amine functionalized transverse oligomeric chain of diols by H-bond. • Dual probe for the detection of nanomolar concentrations of TC and 4-NP. • Static quenching with ground state complexation between N-Cdots and TC /4-NP. • Demonstration of TC and 4-NP detection in real sample matrix: river water and milk. Nitrogen doped carbon dots are emerging as efficient photoluminescent probes for wide range of sensing applications. A simple strategy of synthesizing highly ordered nitrogen doped carbon dots (named here as N-CD arg) is developed by thermal conjugation of 1, 4-Butanediol with L-Arginine. It led to formation of self-assembled transverse carbon chains through oligomerization of 1,4-Butanediol and conjugation with L-Arginine. The structural, morphological and compositional analysis of the N-CD arg is confirmed from 1H and 13C NMR, mass spectroscopy, FT-IR, higher resolution transmission electron microscopy and X-ray photoelectron spectroscopy. It exhibited bright bluish photoluminescence with PL quantum yield of 11 %. Under optimized pH and contact time, the probe solution of N-CD arg exhibited dual sensing for the detection of tetracycline (TC) and 4-nitrophenol (4-NP) via PL quenching proportional, which followed Stern-Volmer relation. The linear PL quenching response for TC is in the range of 0.5 μM to 60 μM with a limit of detection (LOD) of 103 nM; while the linear range for 4-NP is 0.4 μM to 20 μM, and the LOD is 77 nM. Selectivity of these species have been confirmed against several metal ions, anions, other antibiotics (for TC detection) and different structural analogues of phenols (for 4-NP detection). The ability of the probe to quantitatively detect trace concentrations of TC and 4-NP in real sample matrices like river water and milk has been demonstrated by spike analysis. The mechanism of PL quenching of N-CD arg by TC and 4-NP has been discussed using PL decay lifetime spectroscopy. [ABSTRACT FROM AUTHOR]

We present here a facile method for nonaqueous synthesis of highly crystalline nitrogen-doped carbon dots (N-CDs) via oligomerization of ethylene glycol while heating with β-alanine at 170 °C for 30 min. It exhibited bright bluish photoluminescence (PL) at λemission = 461 nm, corresponding to a relative PL quantum yield of 14.3% and an average PL lifetime of 7.4 ns. High-resolution transmission electron microscopy of N-CDs revealed systematically self-assembled transverse oligomeric chains of ethylene glycol doped with β-alanine to form hexagonal symmetry, and their crystalline nature was revealed from electron diffraction measurement. The structure and composition of N-CDs are deduced from 13C nuclear magnetic resonance, high-resolution mass spectrometry, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy measurements, which collectively suggested oligomerization of β-alanine-doped ethylene glycol. The N-CDs are then demonstrated as an efficient probe for quantitative detection of Cr-(VI) species at different pHs and 4-nitrophenol (4-NP) via PL quenching. The limits of detection (LoD) are deduced from respective linear Stern–Volmer plots, e.g., 1.1 μM for H2CrO4 (at pH 0.9), 2.5 μM for HCrO4– (at pH 3.5), and 0.29 μM for CrO42– (at pH 9.0). The detection of Cr-(VI) is highly selective against several cationic (e.g., Na+, K+, Mg2+, Ca2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, and Pb2+) and anionic (Cl–, F–, PO43–, SO42–, NO3–, CO32–, HCO3–, and AsO43–) interfering agents. Similarly, the LoD of 4-nitrophenol was determined to be 0.4 μM, which is significantly better than structurally similar compounds, e.g., phenols, benzene, and their derivatives. The mechanism of detecting Cr-(VI) and 4-NP by N-CDs has been attributed to a combination of static-type PL quenching and an inner filter effect. Finally, practicality of the detection strategy by our method was assessed by analyzing spiked real samples, e.g., municipality tap water and river water. The accuracy and precision of measuring Cr-(VI) and 4-nitrophenol by our method are comparable with those measured by inductively coupled plasma optical emission spectroscopy and high-performance liquid chromatography, respectively. [ABSTRACT FROM AUTHOR]

Quasi-two-dimensional (2D) perovskites recently came into the focus because of their moisture stability. In addition to ambient air, light illumination could also cause degradation for the film of 2D perovskites; however, few studies have investigated their photostability. Here, we work on light-induced photoluminescence quenching, as well as the degradation of quasi-2D perovskites of PEA2MAn−1PbnI3n+1 (n = 3 nominally, PEA+ = C6H5(CH2)2NH3+, MA+ = CH3NH3+). Light-induced photoluminescence (PL) quenching generally happens with different speeds, depending on the wavelength and intensity of the laser as well as the film's environment. With red light (635 nm) illumination, the film does not decompose into ambient air with an intensity below ~500 mW/cm2, although in general, a higher laser intensity and/or higher photon energy (447 nm) could render the decomposition process easier and faster. On the other hand, when the film is in a vacuum, both light-induced PL quenching and film degradation are significantly suppressed. Furthermore, we find that the multiphase of n = 1, 2, 3 in the PEA2MA2Pb3I10 film decomposes together and that the degradation processes begin with the collapses of the crystalline structures. [ABSTRACT FROM AUTHOR]

Monitoring the blood concentration of banoxantrone (AQ4N) is important to evaluate the therapeutic efficacy and side effects of this new anticancer prodrug during its clinical applications. Herein, we report a fluorescence method for AQ4N detection through the modulation of the molecule-like photoinduced electron transfer (PET) behavior of gold nanoclusters (AuNCs). AQ4N can electrostatically bind to the surface of carboxylated chitosan (CC) and dithiothreitol (DTT) co-stabilized AuNCs and quench their fluorescence via a Coulomb interaction-accelerated PET process. Under optimized experimental conditions, the linear range of AQ4N is from 25 to 200 nM and the limit of detection is as low as 5 nM. In addition, this assay is confirmed to be reliable based on its successful use in AQ4N determination in mouse plasma samples. This work offers an effective strategy for AQ4N sensing based on fluorescent AuNCs and widens the application of AuNCs in clinical diagnosis and pharmaceutical analysis.

The strong light-matter interaction and naturally passivated surfaces of van der Waals materials make heterojunctions of such materials ideal candidates for high-performance photodetectors. In this study, we fabricated SnS 2 /MoS 2 van der Waals heterojunctions and investigated their photoelectric properties. Using an applied gate voltage, we can effectively alter the band arrangement and achieve a transition in type II and type I junctions. It is found that the SnS 2 /MoS 2 van der Waals heterostructures are type II heterojunctions when the gate voltage is above -25 V. Below this gate voltage, the heterojunctions become type I. Photoelectric measurements under various wavelengths of incident light reveal enhanced sensitivity in the ultraviolet region and a broadband sensing range from 400 to 800 nm. Moreover, due to the transition from type II to type I band alignment, the measured photocurrent saturates at a specific gate voltage, and this value depends crucially on the bias voltage and light wavelength, providing a potential avenue for designing compact spectrometers.

Long charge carrier diffusion length and large grain size are commonly believed to be inherent properties of highly luminescent polycrystalline thin‐film semiconductors. However, exactly these two properties make luminescence very susceptible to quenching by just one strongly quenching defect state if present in each grain. Moreover, when the number of quenchers per grain is small (say 1–10), it varies greatly from grain to grain, purely for statistical reasons. These fluctuations, which resemble digital signal switching, can be one of the reasons for large differences between the luminescence brightness of different grains in polycrystalline films. This and other peculiarities of photoluminescence in systems where the number of strong quenchers per grain/crystallite is small is discussed in detail using metal halide perovskites as examples. [ABSTRACT FROM AUTHOR]

Organic solar cells have the potential to become the cheapest form of electricity. Rapid increase in the power conversion efficiency of organic solar cells (OSCs) has been achieved with the development of non-fullerene small-molecule acceptors. Next generation photovoltaics based upon environmentally benign “green solvent” processing of organic semiconductors promise a step-change in the adaptability and versatility of solar technologies and promote sustainable development. However, high-performing OSCs are still processed by halogenated (non-environmentally friendly) solvents, so hindering their large-scale manufacture. In this perspective, we discuss the recent progress in developing highly efficient OSCs processed from eco-compatible solvents, and highlight research challenges that should be addressed for the future development of high power conversion efficiencies devices.

In this study, we investigated mechanisms of photoinduced electron transfer from a conjugated polymer (poly(2- methoxy-5-(2-ethylhexyloxy) 1,4-phenylenevinylene (MEH-PPV) to titanium dioxide (TiO2) nanoparticles (acceptor) through steady-state photoluminescence (PL) spectroscopy. Since mixed phase TiO2 has better photocatalytic compared to single phase, it is an efficient charge separation process during photoexcitation of polymer nanocomposites by incorporating the mixed phase TiO2 nanoparticles into the MEH-PPV polymer matrix through in situ polymerization. Structural characterization revealed only physical interaction between the polymer matrix and dispersed nanoparticles. The absorbance spectra of nanocomposites also indicated the absence of ground state complex formation. Luminescence quenching of polymer nanocomposites compared to pristine MEH-PVV signifies the charge transfer taking place at the MEH-PPV/TiO2 interfaces. Thus, the MEH-PPV/mixed phase TiO2 nanocomposite serves as an active layer for photovoltaic application. [ABSTRACT FROM AUTHOR]

Device grade quantum dots (QDs) require QDs ensembles to retain their original superior optical properties as in solution. QDs with thick shells are proven effective in suppressing the inter‐dot interaction and preserving the emission properties for QDs solids. However, lattice strain–induced defects may form as the shell grows thicker, resulting in a notable photoluminescence quenching. Herein, a well‐type CdxZn1−xS/CdSe/CdyZn1−yS QDs is proposed, where ternary alloys CdZnS are adopted to match the lattice parameter of intermediate CdSe by separately adjusting the x and y parameters. The resultant thick‐shell Cd0.5Zn0.5S/CdSe/Cd0.73Zn0.27S QDs reveal nonblinking properties with a high PL QY of 99% in solution and 87% in film. The optimized quantum dot light‐emitting diodes (QLEDs) exhibit a luminance of 31547.5 cd m−2 at the external quantum efficiency maximum of 21.2% under a bias of 4.0 V. The shell thickness shows great impact on the degradation of the devices. The T50 lifetime of the QLEDs with 11.2 nm QDs reaches 251 493 h, which is much higher than that of 6.5 and 8.4 nm QDs counterparts. The performances of the well‐type thick‐shell QLEDs are comparable to state‐of‐the‐art devices, suggesting that this type of QDs is a promising candidate for efficient optoelectronic devices. [ABSTRACT FROM AUTHOR]

Nitrogen-doped graphene quantum dots (N-GQDs) with high blue fluorescence efficiency were synthesized by the hydrothermal method from p-Phenylenediamine and p-Coumaric acid. The N-GQDs possess several superiorities, most significantly in excellent solubility and superior photostability. Besides, the as-prepared N-GQDs exhibit a uniform size distribution with a diameter of about 3.8 ± 0.5 nm. After dispersing the N-GQDs in water, the formed aqueous solution still presents a stable and homogeneous phase even after 2 months at room temperature. The N-GQD dispersion was further utilized as sensing probes for the selective detection of copper ions (Cu2+), which is realized by the photoluminescence (PL) quenching of N-GQDs after adding Cu2+. The detection limit for Cu2+ was found to be 57 nM L−1, with superior selectivity in the presence of other commonly interfering metal ions. The presented results in this study provide a facile and high-efficiency method for synthesizing N-GQDs, with ultra-high detectivity and selectivity for Cu2+ detection, offering numerous opportunities for the development of biosensing, bioimaging, environment monitoring, and others. • We reported a rapid and sensitive fluorescence nanomaterials sensor with satisfactory selectivity. • The as-prepared N-GQDs exhibited excitation-independent behavior and high optical stability. • The fluorescence intensity of the N-GQDs could be greatly quenched by adding a small amount of Cu2+ ions. • The linearity range is 0–10 μM with a detection limit of 57 nM. [ABSTRACT FROM AUTHOR]

In this article, we report the synthesis and characterization of silver dispersed poly(m-toluidine-co-2-bromoaniline) copolymer synthesized by chemical oxidative polymerization method. The synthesized copolymer composites were subjected to different analytical characterization methods, such as FT-IR, UV, XRD, SEM, photoluminescence and electrical conductivity studies. All the polymer samples are found to be soluble in common organic solvents. UV absorption spectra show a red shift when silver nanoparticles are dispersed in the copolymer. The characteristic peaks observed in FT-IR spectra confirm the formation of the copolymer. XRD pattern reveals the crystalline nature of the copolymer composites and sharp peaks in the spectra confirm the presence of silver particles. The silver nanoparticles change the surface morphology in the form of perfect encapsulation. The electrical conductivity of the polymer composites is found to vary from 10−4 S/cm to 10−6 S/cm. PL study reveals the charge transfer between the copolymer and the silver particles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tb3+ and Eu3+ ions chelate with dipicolinic acid (DPA), the products of which are highly photoluminescent. • Iron oxide nanoparticles are developed to magnetically assist photoluminescence detection of DPA. • Much lower detection limit for DPA can be achieved after magnetic removal of free Tb3+ or Eu3+ ions. • The concentration of Cu2+ ions can be estimated by photoluminescence quenching of Tb3+- or Eu3+-DPA complex. • Tb3+ and Eu3+ ions are compared each other for DPA and Cu2+ detection sensitivities. Dipicolinic acid (DPA) is a chelate capable of binding to a variety of lanthanide ions to make them luminescent in the visible range. Based on this property and also assisted by magnetic separation, we report a strategy for the sensitive detection of DPA. Poly(acrylic acid)-coated iron oxide nanoparticles (IONPs) serve as a magnetic carrier to deliver only a necessary amount of Tb3+ ions to DPA in a sample solution. This enables photoluminescence measurement of the Tb3+-DPA complex with minimal background noise. The obtained detection limit, which is as low as 0.236 nM, is more than two orders of magnitude lower than that of the assay not assisted by magnetic separation. Not only does this method possess a potential for diagnosing anthrax, given that DPA is a major constituent of Bacillus anthracis spores, but it is also useful for detecting aqueous Cu2+ ions through the luminescence quenching effect. High sensitivity with a detection limit of 54 nM [Cu2+] is demonstrated using the Eu3+-DPA complex. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) and few-walled carbon nanotubes (FWCNTs) mixed in poly(3-hexylthiophene-2,5-diyl) (P3HT) were prepared for application in organic solar cells (OSCs) as photoactive materials. ZnO was synthesized by microwave-assisted sol-gel method. Improved properties were found for the nanocomposite with 3 wt% of FWCNTs concentration. XRD revealed the hexagonal wurtzite structure of ZnO and the nanocomposites (ZnO-FWCNTs) showed both hexagonal wurtzite and carbon structure. UV/Vis/NIR and PL studies revealed a relatively higher photon absorption efficiency and emission intensity from the ZnO-3% FWCNTs. PL intensity of P3HT was quenched from the sample P3HT:ZnO-3% FWCNTs with the ratio of 1:1, indicating charge transfer phenomena between the electron donor (P3HT) and an acceptor (ZnO-FWCNTs) materials. FESEM showed well-mixed ZnO nanorods with P3HT. Current-voltage measurements indicated an improved electrical conductivity for P3HT:ZnO-3% FWCNTs (ratio 1:1). The obtained results suggest that this sample can potentially improve the photoelectrical conversion efficiency of the OSCs. [ABSTRACT FROM AUTHOR]

Quinacridone, a red pigment, was hybridized with a synthetic hectorite by a mechanochemical reaction. Though quinacridone was not photoluminescent, the products were photoluminescent and the photoluminescence quantum yield was 0.89 when the dye loading was 0.00009 g dye/g clay. The product was dispersed in water to give stable suspensions with varied viscosities depending on the concentration of the hybrids. The photoluminescence of the aqueous suspension was quenched by Cr3+, Co2+, Cu2+, Fe2+, Ni2+ and Pb2+ as described by linear Stern-Volmer plots at the concentration of 1–600 ppm. Among the tested metal ions, Cr3+ gave the most efficient quenching (the K SV value of 0.0125). The quenching of the photoluminescence of the quinacridone-synthetic hectorite hybrid was applicable to detect Cu2+ and Cr3+ at ppb level. [Display omitted] • Hybridization of quinacridone and smectites was achieved by a solvent-free mechanochemical reaction. • The hybrid of quinacridone and synthetic hectorite was luminescent (Photoluminescence quantum yield was 0.89). • Thanks to swelling characteristic of the smectite, the hybrid was dispersible in water as a stable colloidal suspension. • Luminescence of the aqueous suspension was quenched by Cu2+ at a low concentration of 1.5 ppb. [ABSTRACT FROM AUTHOR]

Abstract 2D vertical van der Waals (vdW) heterostructures with atomically sharp interfaces have attracted tremendous interest in 2D photonic and optoelectronic applications. Band alignment engineering in 2D heterostructures provides a perfect platform for tailoring interfacial charge transfer behaviors, from which desired optical and optoelectronic features can be realized. Here, by developing a two‐step chemical vapor deposition strategy, direct vapor growth of monolayer PbI2 on monolayer transition metal dichalcogenides (TMDCs) (WS2, WSe2, or alloying WS2(1−x)Se2x), forming bilayer vertical heterostructures, is demonstrated. Based on the calculated electron band structures, the interfacial band alignments of the obtained heterostructures can be gradually tuned from type‐I (PbI2/WS2) to type‐II (PbI2/WSe2). Steady‐state photoluminescence (PL) and time‐resolved PL measurements reveal that the PL emissions from the bottom TMDC layers can be modulated from apparently enhanced (for WS2) to greatly quenched (for WSe2) compared to their monolayer counterparts, which can be attributed to the band alignment–induced distinct interfacial charge transfer behaviors. The band alignment nature of the heterostructures is further demonstrated by the PL excitation spectroscopy and interlayer exciton investigation. The realization of 2D vertical heterostructures with tunable band alignments will provide a new material platform for designing and constructing multifunctional optoelectronic devices.

Quasi-two-dimensional (2D) perovskites recently came into the focus because of their moisture stability. In addition to ambient air, light illumination could also cause degradation for the film of 2D perovskites; however, few studies have investigated their photostability. Here, we work on light-induced photoluminescence quenching, as well as the degradation of quasi-2D perovskites of PEA2MAn−1PbnI3n+1 (n = 3 nominally, PEA+ = C6H5(CH2)2NH3+, MA+ = CH3NH3+). Light-induced photoluminescence (PL) quenching generally happens with different speeds, depending on the wavelength and intensity of the laser as well as the film’s environment. With red light (635 nm) illumination, the film does not decompose into ambient air with an intensity below ~500 mW/cm2, although in general, a higher laser intensity and/or higher photon energy (447 nm) could render the decomposition process easier and faster. On the other hand, when the film is in a vacuum, both light-induced PL quenching and film degradation are significantly suppressed. Furthermore, we find that the multiphase of n = 1, 2, 3 in the PEA2MA2Pb3I10 film decomposes together and that the degradation processes begin with the collapses of the crystalline structures.

The singlet exciton diffusion length was measured in a small molecule electron donor material DR3TBDTT using fluorescence quenching at a planar interface with a cross-linked fullerene derivative. The one-dimensional exciton diffusion length was increased from ~16 to ~24 nm by annealing the film in carbon disulfide solvent vapor. Planar heterojunction solar cells were fabricated using bilayers of these materials and it was found that solvent vapor annealing increased the short circuit current density by 46%. This can be explained by improved exciton harvesting in the annealed bilayer. Image 1 • Exciton diffusion in DR3TBDTT is engineered by solvent vapor annealing. • Bilayer OPV device with well-defined donor-acceptor interface is fabricated for investigating effect of exciton diffusion. • Optical model confirms the significance of exciton diffusion in determining bilayer device efficiency. [ABSTRACT FROM AUTHOR]

The attachment of pyridyl substituted porphyrin molecule to the surface of CdSe/ZnS quantum dots in solutions is realized in the competition with capping ligand TOPO molecules resulting in the specific change of photoluminescence for the quantum dots across the temperature range of 77–290 K. We have shown that fixation of alone quantum dots or quantum dot-porphyrin nanoassemblies on quartz substrate changes significantly temperature dependence of photoluminescence. In contrast to the samples in a glass-forming solution no phase transition of the TOPO capping layer was observed upon removal of the capping layer. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) van der Waals (vdW) heterostructures have been proven as a predominant platform to investigate the electronic and optoelectronic properties in 2D heterostructures theoretically and experimentally. Here, we have fabricated and characterized artificial vdW heterostructures by stacking 2D MoS 2 nanosheets on the Bi 2 Te 3 film which is a representative Z2 topological insulator. We have systematically studied the photoluminescence (PL) properties of the MoS 2 /Bi 2 Te 3 heterostructure and compared them with the results of MoS 2 nanosheets on SiO 2 /Si. We demonstrated that MoS 2 shows a significant PL quenching in the MoS 2 /Bi 2 Te 3 heterostructure. Combined with density-function theory (DFT) calculations, we conclude that the PL quenching is a result of the efficient separation of photo-excited electrons and holes induced by the build-in interfacial electric field and charge transfer between different layers in the MoS 2 /Bi 2 Te 3 heterostructure. • We successfully fabricated MoS 2 /Bi 2 Te 3 heterostructure. • Significant photoluminescence quenching for MoS 2 /Bi 2 Te 3 heterostructure is observed. • Combined experimental phenomenon with DFT calculations. [ABSTRACT FROM AUTHOR]

Abstract Carbon dots (CDs) responsive to external stimuli that cause changes in their optical properties are in high demand. Herein, we present a microwave synthesis of highly fluorescent CDs derived for the first time from β-resorcylic acid (henceforth referred as R-CDs) in sulfuric acid (H 2 SO 4) medium. Interestingly, the as-synthesized R-CDs showed tunable optical properties with three distinguishable colors (green/blue/blue-violet) depending on pH under UV irradiation. Spectral analyses and mechanistic studies revealed that the fluorescence switch is due to the deprotonation of the oxygenous surface functionalities in the R-CDs. The pH-dependent color switchability was tested in a number of cycles under UV light by adding 0.1 (M) HCl and NaOH. Although several mechanisms involving the complex photoluminescence of CDs have been reported, we propose here that the photoluminescence behavior of the CDs can be tuned by deprotonation of the oxygenous surface functionalities. Moreover, these R-CDs can be used as a potential visual indicator of three different pH ranges, and as highly selective and sensitive sensing medium for Fe3+ ions. The limit of detection was calculated to be 0.43 μM. Graphical abstract Image 1 Highlights • Carbon dots (R-CDs) were synthesized from β-resorcylic acid using microwave irradiation. • R-CDs showed pH dependent tunable optical properties under UV irradiation. • Two prototropic equilibria (Carboxylic acid ↔ carboxylate and phenol ↔ phenolate) controls photophysical properties. • R-CDs showed high selectivity and sensitivity towards Fe3+ metal ions. [ABSTRACT FROM AUTHOR]

Abstract For further development of organic light-emitting diodes (OLEDs), an understanding of the amorphous structures and photoluminescence properties of organic emitting layers is needed. In this study, the molecular orientation, density, and photoluminescence properties of tris(8-hydroxyquinolinato)aluminum (Alq 3) films vacuum-deposited using various substrate temperatures and deposition rates were investigated. The molecular orientation and density of the Alq 3 films exhibited clear dependence on the substrate temperature, which was caused by the change of molecular kinetic mobility during deposition. We found that photoluminescence quenching was stronger in Alq 3 films fabricated at lower substrate temperatures and higher deposition rates. This photoluminescence quenching was not related to molecular orientation and film density and likely originated from the inclusion of impurities in the films. These results indicate that decreasing the amount of impurities in films by increasing substrate temperature or decreasing deposition rate is crucial to achieve the maximum photoluminescence performance from films. Graphical abstract Image 1 Highlights • Alq 3 films were vacuum-deposited using various deposition conditions. • Deposition conditions affected molecular orientation and density of Alq 3 films. • Photoluminescence was quenched for Alq 3 films fabricated at specific conditions. • Photoluminescence quenching resulted from inclusion of impurities in Alq 3 films. [ABSTRACT FROM AUTHOR]