Photoluminescence Detection Research Articles

The Influence of Thickness and Spectral Properties of Green Color-Emitting Polymer Thin Films on Their Implementation in Wearable PLED Applications.

A systematic investigation of optical, electrochemical, photophysical, and electrooptical properties of printable green color-emitting polymer (poly(9,9-dioctylfluorene-alt-bithiophene)) (F8T2) and spiro-copolymer (SPG-01T) was conducted to explore their potentiality as an emissive layer for wearable polymer light-emitting diode (PLED) applications. We compared the two photoactive polymers in terms of their spectral characteristics and color purity, as these are the most critical factors for wearable lighting sources and optical sensors. Low-cost, solution-based methods and facile architecture were applied to produce rigid and flexible light-emitting devices with high luminance efficiencies. Emission bandwidths, color coordinates, operational characteristics, and luminance were also derived to evaluate the device's stability. The tuning of emission's spectral features by layer thickness variation was realized and was correlated with the interplay between H-aggregates and J-aggregates formations for both conjugated polymers. Finally, we applied the functional green light-emitting PLED devices based on the two studied materials for the detection of Rhodamine 6G. It was determined that the optical detection of the R6G photoluminescence is heavily influenced by the emission spectrum characteristics of the PLED and changes in the thickness of the active layer.

Two Stable Pillar-Layered Zn-LMOFs for Highly Fluorescence Sensing of Inorganic Pollutants and Nitro Aromatic Compounds in Water.

Luminescent metal-organic frameworks (LMOFs) are a potential class of functional materials for the photoluminescent detection of a wide range of analytes as well as for the detection of pollutants in wastewater. Herein, by using the pillar-layered strategy, two new luminescence Zn-LMOFs (JLU-MOF222 and JLU-MOF223) were successfully solvothermal synthesized. The 2D layers are both consisting of Zn2+ and TPHC [TPHC = (1,1':2',1″-terphenyl)-3,3″,4,4',4″,5'-hexacarboxylic acid] ligands and then pillared by the different N-donor ligands to form the 3D Zn-LMOFs with fsh topology. Benefiting from the uncoordinated carboxylate sites, uncoordinated N atom, or -NH2 group in the pillaring ligands and excellent stability in pH = 2-13 aqueous phase, JLU-MOF222 and JLU-MOF223 not only can sensitively detect trace amounts of inorganic pollutants (Fe3+, Cr2O72-) and nitro aromatic compounds TNP and 2,4-DNP (TNP = 2,4,6- trinitrophenol, 2,4-DNP = 2,4-dinitrophenol) through luminescence quenching but also exhibit high selectivity of other anti-interference competing analytes. The two new Zn-LMOFs can be used as potential luminescent sensors for pollutant detection in water due to their high KSV and low limit of detection (LOD).

High-yield preparation of g-C3N4 nanosheet suspension by a two-step mechanochemical technique

Compared with the bulk g-C3N4, g-C3N4 nanosheets have the advantages such as larger specific surface area and more active sites, making them more promising in optoelectronic applications. However, the current methods for preparing g-C3N4 nanosheets have some disadvantages such as low yield, long exfoliation time and high energy consumption. Herein, a two-step mechanochemical method combining wet ball milling with ultrasonic-ball milling has been proposed, with a high yield of up to 31.8% for suspensible g-C3N4 nanosheets. Adding YSZ balls during the ultrasound process can effectively improve the cutting efficiency of the g-C3N4 sheets, thereby increasing the yield of the suspensible nanosheets. The stability of g-C3N4 suspensions were relatively high, and the concentration of the suspensions remained above 87% after standing 24 h. The spectra of the nanosheets obtained through the two-step process had a single emission peak of 435 nm, which was suitable for photoluminescence detection.

Thiazole-derived pyrazin-2-carbohydrazide chemosensors: Colorimetric & photoluminescent detection of silver ions for theoretical, environmental, and cell imaging

In this work, a simple and versatile chemosensor receptor TZPYZ was synthesized through the combination of thiazole with pyrazine-2-carbohydrazide, resulting in a confirmed chemical structure via various analytical techniques including FT-IR, 1H, and 13C Nuclear Magnetic Resonance Spectroscopy, as well as High-Resolution Mass Spectroscopy analysis. TZPYZ exhibits specific colorimetric and photoluminescent responses to Ag+ ions in a solvent solution consisting of DMSO and H2O (7:3, v/v). Upon addition of Ag+ ions, noticeable changes in absorption spectra occur, resulting in a visible color change from pale yellow to blue. Additionally, an enhanced emission intensity with wavelength at 523 nm, when excited at 410 nm. Notably, TZPYZ demonstrated exceptional selectivity for Ag+ ions over other metal cations, achieving a detection limit (LOD) of 10.6 × 10−9 M and 6.74 × 10−9 M and using the UV–visible & photoluminescent titration method. Interference studies indicated minimal disruption from other metal ions on emission at 523 nm, highlighting TZPYZ discerning capability for Ag+ ions. With a binding affinity of 3.622 × 10−11 M−1, TZPYZ proved effective in detecting Ag+ ions across various water samples, showcasing its practical utility. The mechanism of interaction between TZPYZ and Ag+ ions was investigated using various experimental techniques, including Job’s plot, Benesi-Hildebrand investigations, 1H NMR, and HRMS analysis. Test strips coated with TZPYZ showed selective detection of Ag+ ions, indicating its potential for on-site applications. Furthermore, DFT computations provided insights into the structural and electronic properties of TZPYZ and its complex with Ag+ ions, further elucidating the binding mechanism and stability of the complex. In addition, TZPYZ demonstrated compatibility with biological systems, as fluorescence imaging tests on MCF-7 breast cancer cells confirmed both its non-cytotoxic nature and its proficiency in detecting intracellular silver ions. Based on these findings, TZPYZ is highlighted as a highly sensitive and selective chemosensor for Ag+ ions, with promising applications in environmental analysis and bioimaging.

Two-dimensional metal–organic framework for post-synthetic immobilization of graphene quantum dots for photoluminescent sensing

Immobilization of graphene quantum dots (GQDs) on a solid support is crucial to prevent GQDs from aggregation in the form of solid powder and facilitate the separation and recycling of GQDs after use. Herein, spatially dispersed GQDs are post-synthetically coordinated within a two-dimensional (2D) and water-stable zirconium-based metal–organic framework (MOF). Unlike pristine GQDs, the obtained GQDs immobilized on 2D MOF sheets show photoluminescence in both suspension and dry powder. Chemical and photoluminescent stabilities of MOF-immobilized GQDs in water are investigated, and the use of immobilized GQDs in the photoluminescent detection of copper ions is demonstrated. Findings here shed the light on the use of 2D MOFs as a platform to further immobilize GQDs with various sizes and distinct chemical functionalities for a range of applications.

Accurate detection and intelligent classification of solar cells defects based on photoluminescence images: A novel study on the optimized YOLOv5 model

In the production process of solar cells, inevitable faults such as cracks, dirt, dark spots, and scratches may occur, which could potentially impact the lifespan and power generation efficiency of solar cells. Addressing this issue, this paper combines neural networks with photoluminescence detection technology and proposes a novel neural network model for the classification and grading of defects in solar cells. Firstly, the YOLOv5 model is optimized and adjusted for algorithm and network structure. The optimization process is divided into three parts: global optimization of the network structure, optimization of the neck network structure, and optimization of the head structure, each addressing specific issues in recognition, detection, and classification. The impact of the optimized network model on recognition and detection speed is analyzed, and solutions are proposed to address any observed effects. Additionally, an iterative update of neural network hyperparameter combinations is performed for solar cell defect identification. Finally, using the ultimately optimized model structure in conjunction with the optimal hyperparameter combination, comparative experiments are conducted on neural networks for different target identification using the photoluminescence characteristics dataset of solar cells. The recognition improvement of the optimized model and its differences from other models are analyzed.

Investigation of glucose biosensors by non-enzymatic photoluminescent detection using oleic acid treated Ag2S nanoparticles

The immobilization of carboxylic acid moieties on the surface of nanoparticles to promote the development of non-enzymatic detection of target molecules (sensors) with better feasibility and selectivity has been investigated. This work is focused on treating Ag2S nanoparticles with Oleic acid, a potential carboxylic acid moiety with good stereochemical compatibility, photochemical responses, photoluminescence (PL) quantum yield, and biocompatibility. The hydrothermally synthesized Ag2S was crystalline in nature with a monoclinic crystal system, as inferred from X-ray diffractograms. The surface morphology of Ag2S studied using the SEM micrographs showed nearly spherical and fused particles. ATR-FTIR was recorded by the compensation method in the wavenumber range 600–4000 cm−1 and the changes in the chemical composition of pristine Ag2S and Oleic acid-treated Ag2S (with or without glucose molecules) were investigated. UV–Vis analysis was carried out to establish the absorption region of the respective nanoparticles, and the corresponding inferred excitation wavelength (396 nm) was fixed for the PL analysis. Photoluminescence spectra (PL) of Ag2S with oleic acid and glucose at various concentrations showed a reduction in PL intensity as glucose concentration increased. This PL reduction arises due to various oxidation processes that take place on the large surface of Oleic acid-treated Ag2S. Chronoamperometric studies were used to analyze the electrocatalytic glucose oxidation that occurs in Ag2S nanoparticles with Oleic acid with a low-cost procedure. The concentration of glucose was varied from 0.25 to 30 mM, and the significant sensing abilities of the oleic acid-treated Ag2S were demonstrated.

Suppression of photo-induced electron transfer of alcaftadine for its photoluminescence detection in aqueous humor

A green, facile and selective fluorimetric approach was described for estimating alcaftadine (ALC) in its pure form, eye drop formulation, and artificial aqueous humor for the first time. The developed approach depends on the suppression of the photoinduced electron transfer (PET) impact of the lone pair of the N-atom of the piperidine ring of ALC. PET suppression was attained by using 0.3 M acetic acid as an efficient protonating agent. By virtue of this phenomenon, ALC was quantified from 50 to 400 ng mL−1 with a very low detection and quantitation limit of 2.22 and 6.72 ng mL−1, respectively. Additionally, the presented method was employed for estimating the target drug in artificial aqueous humor and observably there is no significant interference from the aqueous humor matrix.

Fast ultraviolet detection response achieved in high-quality Cs3Bi2Br9 single crystals grown by an improved anti-solvent method

This article successfully grew high-quality bismuth-based inorganic perovskite Cs3Bi2Br9 single crystals with strong stability that can be applied in the field of ultraviolet light detection using the antisolvent growth technique.

ОБНАРУЖЕНИЕ АНТИБИОТИКОВ В МОЛОКЕ ПО ЕГО ФОТОЛЮМИНЕСЦЕНТНЫМ СВОЙСТВАМ

The use of antibiotics in the breeding of farm animals is an urgent problem with regard to food safety. For the dairy industry, the detection of residual amounts of antibiotics is crucial because of their inhibitory effect on fermentation processes. The most promising are optical screening methods for detecting these substances in milk and its processed products. Using optical sensors, it is possible to recognize a wide range of substances with high sensitivity and detect the residual content of various antibiotics, including the penicillin group. (Research Purpose) The research purpose is studying the possibility of detecting antibiotics of the penicillin group in milk by its photoluminescent properties. (Materials and methods) The spectral characteristics of milk excitation were measured on a CM 2203 spectrofluorimeter in the range from 200-500 nanometers. The control measurement of the antibiotic content in milk was carried out using BIOEASY 4in1 BSCT test kits. (Results and discussion) Four waves with a maximum length of 290, 324, 360 and 445 nanometers were present in the excitation spectrum of all milk samples. The spectra are measured and the integral fluxes of milk photoluminescence are calculated. (Conclusions) The presence of penicillin antibiotics in milk affects the optical properties of photoluminescence. The most informative are the excitation wavelength 360 and the photoluminescence detection range at 400-650 nanometers. The conducted studies confirm the possibility of qualitative determination of the presence of antibiotics in milk at a concentration of 0.001 mg/kg and above, which is 3-4 times more accurate than using the method with BIOEASY 4in1 BSCT test kits.

Immobilization of europium and terbium ions with tunable ratios on a dispersible two-dimensional metal-organic framework for ratiometric photoluminescence detection of D2O.

A two-dimensional zirconium-based metal-organic framework (2D Zr-MOF), ZrBTB (BTB = 1,3,5-tri(4-carboxyphenyl)benzene), is used as a platform to simultaneously immobilize terbium ions and europium ions with tunable ratios on its hexa-zirconium nodes by a post-synthetic modification. The crystallinity, morphology, porosity and photoluminescence (PL) properties of the obtained 2D Zr-MOFs with various europium-to-terbium ratios are investigated. With the energy transfer from the excited BTB linker to the installed terbium ions and the energy transfer from terbium ions to europium ions, a low loading of immobilized europium ions and a high loading of surrounding terbium ions in the 2D Zr-MOF result in the optimal PL emission intensities of europium; this phenomenon is not observable for the physical mixture of both terbium-installed ZrBTB and europium-installed ZrBTB. The role of installed terbium ions as efficient mediators for the energy transfer from the excited BTB linker to the installed europium ion is confirmed by quantifying PL quantum yields. As a demonstration, these materials with modulable PL characteristics are applied for the ratiometric detection of D2O in water, with the use of the stable emission from the BTB linker as the reference. With the strong emission of immobilized europium ions and the good dispersity in aqueous solutions, the optimal bimetal-installed ZrBTB, Eu-Tb-ZrBTB(1 : 10), can achieve the sensing performance outperforming those of the terbium-installed ZrBTB, europium-installed ZrBTB and the physical mixture of both.

Dual modifications of sensitizers and lanthanide ions on a two-dimensional zirconium-based metal–organic framework for photoluminescent detection

Luminescent 2D Zr-based MOFs for sensing Fe(iii) ions were synthesized by dual post-synthetic modifications of photosensitizing ligands and terbium ions.

Photoluminescent and electrochemiluminescent detection of homocysteine based on bifunctional cyclometalated iridium(III) complex

A photoluminescent (PL) and electrochemiluminescent (ECL) chemodosimeter for homocysteine (Hcy) determination was developed based on a bifunctional cyclometalated iridium(III) complex (pba)2Ir(dcbpy). (pba)2Ir(dcbpy) was prepared by using 4′-(2-pyridyl)-benzaldehyde (pba) as main ligand and 2,2′-bipyridyl-4,4′-dicarboxylic acid (dcbpy) as ancillary ligand. The existence of aldehyde group on the main ligand and dicarboxylic acid groups on the ancillary ligand endows (pba)2Ir(dcbpy) good water solubility. Importantly, the aldehyde group on the main ligand also furnishes the chemodosimetric active site, which could react with Hcy highly in neutral buffer solution based on a unique cyclization reaction with aminoalkylthiol group to produce a binding adduct, enhancing both PL and ECL signal. The photophysical and ECL properties of (pba)2Ir(dcbpy) in the absence and presence of Hcy were investigated and the response mechanism of the luminescence enhancement was confirmed by mass spectrum. Both PL and ECL measurements exhibited good linear relationships to the Hcy with the detection of limit at micro-molar level. More significantly, (pba)2Ir(dcbpy) possessed a relatively high discriminating ability to differentiate Hcy from structurally related molecule (cysteine) under neutral buffer conditions. The PL and ECL chemodosimeter based on cyclometalated iridium(III) complex with specific active site is universal to the analysis of other targets, thus opening a new avenue for the application of cyclometalated iridium(III) complex in PL and ECL field.

Near-infrared photoluminescent detection of serum albumin using single-walled carbon nanotubes locally functionalized with a long-chain fatty acid

Serum albumin (SA) is a protein found in biofluids that is useful for diagnosing kidney and liver-related diseases. Single-walled carbon nanotubes (SWCNTs) showing photoluminescence (PL) in the near-infrared (NIR) region are prospective candidates for diagnosis NIR probes. Their NIR PL enhancement has been reported by defect introduction techniques based on local chemical functionalization of SWCNTs. The locally functionalized (lf-)SWCNTs exhibit a bright defect PL (>1000 nm) from the defect sites and its sensitive wavelength shifts in response to surrounding dielectric atmospheres have been reported. Here, we used the sensitive defect PL responses of lf-SWCNTs to establish a NIR sensing system for SA detection. A palmitic acid group that binds to SA strongly and selectively, was functionalized at the defect site of lf-SWCNTs (lf-SWCNTs-p). Compared to typical PL of unmodified SWCNTs, selective defect PL red-shifts (of 2.5 nm max.) were clearly observed according to the addition of SA in phosphate-buffered saline. The defect PL responsiveness could detect different SA from human, bovine, and mouse. The red-shifts of the defect PL occurred by formation of a high dielectric environment based on the specific binding between SA and the palmitic acid groups on the defect sites. The lf-SWCNTs-p detected SA-spiked serum and albuminuria of diabetic mouse in body fluids. The findings show that the lf-SWCNTs-p offer an NIR PL analytical tool for SA in body fluids applicable to a disease diagnosis and expand the bioapplications of lf-SWCNTs based on their molecular design-based defect engineering.

Magnetic separation-enhanced photoluminescence detection of dipicolinic acid and quenching detection of Cu(II) ions

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.

Luminescent properties of the structures with embedded silicon nanoclusters: Influence of technology, doping and annealing (Review)

Detection of photoluminescence (PL) in traditionally non-luminescent Si material (a typical indirect band semiconductor) attracts great attention both in the scientific aspect and for applications in the field of micro- and nanoelectronics and photoelectronics. Despite the success in technology and understanding of many features inherent to its PL characteristics, many problems have not yet been resolved. In particular – what is the origin of PL lines: quantum size, molecular complexes within SiO2, interface or volume localized states, etc. How to achieve the increase in the PL intensity and to provide excitation of it in different parts of the spectrum. The proposed review systematizes results of studies associated with these problems concerning the original technologies for creation of Si nanocrystals (nc-Si) and various research methods. In conclusion, we summarize the results on the properties of nc-Si-SiO2 luminescent structures depending on their technology of synthesis, photo- and structural features and application prospects for micro- and nanoelectronics as well as photoelectronics.

Coloration on Bluish Alginate Films with Amorphous Heterogeneity Thereof.

Using sodium alginate (Alg) aqueous solution containing indigo carmine (IdC) at various concentrations we characterized the rippled surface pattern with micro-spacing on a flexible film as intriguing bluish Alg-IdC iridescence. The characterization was performed using Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, field emission scanning electron microscopy, atomic force microscopy, electron microscopy, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction analysis, and photoluminescence detection. The edge pattern on the film had a maximum depth of 825 nm, a peak-to-peak distance of 63.0 nm, and an average distance of 2.34 nm. The center of the pattern had a maximum depth of 343 nm and a peak-to-peak distance of 162 nm. The pattern spacing rippled irregularly, widening toward the center and narrowing toward the edges. The rippled nano-patterned areas effectively generated iridescence. The ultraviolet absorption spectra of the mixture in the 270 and 615 nm ranges were the same for both the iridescent and non-iridescent film surfaces. By adding Ag+ ions to Alg-IdC, self-assembled microspheres were formed, and conductivity was improved. Cross-linked bluish materials were immediately formed by the addition of Ca2+ ions, and the film was prepared by controlling their concentration. This flexible film can be used in applications such as eco-friendly camouflage, anti-counterfeiting, QR code materials for imaging/sensing, and smart hybrid displays.

Resolving Nonlinear Recombination Dynamics in Semiconductors via Ultrafast Excitation Correlation Spectroscopy: Photoluminescence versus Photocurrent Detection.

We explore the application of excitation correlation spectroscopy to detect nonlinear photophysical dynamics in two distinct semiconductor classes through time-integrated photoluminescence and photocurrent measurements. In this experiment, two variably delayed femtosecond pulses excite the semiconductor, and the time-integrated photoluminescence or photocurrent component arising from the nonlinear dynamics of the populations induced by each pulse is measured as a function of inter-pulse delay by phase-sensitive detection with a lock-in amplifier. We focus on two limiting materials systems with contrasting optical properties: a prototypical lead-halide perovskite (LHP) solar cell, in which primary photoexcitations are charge photocarriers, and a single-component organic-semiconductor diode, which features Frenkel excitons as primary photoexcitations. The photoexcitation dynamics perceived by the two detection schemes in these contrasting systems are distinct. Nonlinear-dynamic contributions in the photoluminescence detection scheme arise from contributions to radiative recombination in both materials systems, while photocurrent arises directly in the LHP but indirectly following exciton dissociation in the organic system. Consequently, the basic photophysics of the two systems are reflected differently when comparing measurements with the two detection schemes. Our results indicate that photoluminescence detection in the LHP system provides valuable information about trap-assisted and Auger recombination processes, but that these processes are convoluted in a nontrivial way in the photocurrent response and are therefore difficult to differentiate. In contrast, the organic-semiconductor system exhibits more directly correlated responses in the nonlinear photoluminescence and photocurrent measurements, as charge carriers are secondary excitations only generated through exciton dissociation processes. We propose that bimolecular annihilation pathways mainly contribute to the generation of charge carriers in single-component organic semiconductor devices. Overall, our work highlights the utility of excitation correlation spectroscopy in modern semiconductor materials research, particularly in the analysis of nonlinear photophysical processes, which are deterministic for their electronic and optical properties.

Determination of Free Charge Carrier Luminescence and Quasi‐Fermi Level Separation in Organic Solar Cells via Transient Photoluminescence Measurements

AbstractThe detection of photoluminescence (PL) is extremely valuable for photovoltaic technologies as it provides direct information about the free charge carrier densities and therefore about the separation of the quasi‐Fermi levels (ΔEF). However, for organic solar cells the PL is strongly dominated by photogenerated excitons that in part decay radiatively before they form free charge carriers via dissociation at a donor/acceptor interface. For this reason, it is impossible to deduce the free charge carrier densities and ΔEF directly from the PL signal. To overcome this severe limitation, a new approach is developed that allows disentangling the luminescence of photogenerated excitons from the one of free charge carriers. Due to the large difference in respective lifetimes—for photogenerated excitons it is ≤ ns whereas for free charge carriers it is in the µs‐range—this is achieved by time‐resolved PL measurements. For highly efficient organic solar cells, it is found that ΔEF determined from these PL transients matches perfectly with the electrical voltage. Moreover, the new method also allows for the determination of ΔEF from mere absorber films without electrodes and thus paves the way for a better understanding of organic solar cells.

Enhanced Photoluminescence Detection of Immunocomplex Formation by Antibody-Functionalized, Ge-Doped Biosilica from the Diatom Cyclotella sp.

Diatoms are single-celled algae that biosynthesize cell walls of biogenic silica called "frustules" that are intricately patterned at the submicron- and nanoscale. In this study, we amplified the intrinsic luminescent properties of antibody-functionalized diatom biosilica frustules for enhanced, label-free, photoluminescence (PL) detection of immunocomplex formation. It was hypothesized that metabolically doped GeO centers in antibody-functionalized diatom biosilica would enhance PL emission associated with nucleophilic immunocomplex formation. Germanium (Ge) was metabolically inserted into the frustule biosilica by two-stage cell cultivation of the centric diatom Cyclotella sp. The biosilica frustules were isolated by hydrogen peroxide treatment and thermally annealed to convert Ge oxides in the biosilica (0.4 wt% Ge) to luminescent GeO centers. The Ge-doped biosilica frustules were then functionalized with Rabbit Immunoglobulin G (IgG). Upon immunocomplex formation with its complimentary antigen goat anti-Rabbit IgG, the Ge-oxide doped, antibody-functionalized frustule biosilica increased the intensity of PL emission by a factor of 2.6 relative to immunocomplex formation by antibody-functionalized frustule biosilica without Ge. It is proposed that the luminescent GeO centers in the Ge-oxide doped frustule biosilica were more sensitive to radiative recombination than luminescent silanol groups in frustule biosilica without Ge, resulting in a higher PL emission upon immunocomplex formation.