High Extinction Coefficient Research Articles

A Hemicyanine‐Based Highly Sensitive and Selective Near‐Infrared Fluorescent Probe for Fe3+ in Aqueous Media

ABSTRACTFerric ion is widely distributed in human cells and an important component of hemoglobin, which can promote the transportation of blood in the human body. Its ability to bind with oxygen is essential for participating in oxidation reactions and enzymatic reactions. Deficiency of iron (III) and excessive accumulation of iron in the blood can cause many health problems in the body, such as anemia, loss of appetite, fibrosis, reduced work routines, and decreased immunity. As a fluorescent dye, cyanine has the advantages of high fluorescence quantum yield, good optical and chemical stability, excitation and emission wavelengths in the near‐infrared region, high molar extinction coefficient, and small influence on pH variation. It is a fluorescent dye that modern scholars choose more. A new near‐IR hemicyanine derivative bearing 1,3‐dithiane moiety was developed as an efficient fluorescence probe 1 for the detection of Fe3+ in aqueous medium (THF/H2O, 1:1, v:v). This near‐IR fluorescence probe 1 exhibits high sensitivity and selectivity toward Fe3+ sensing with detection limit of 0.5 μM under lager scope of pH value (pH = 2–12).

Synthesis and characterization of new organometallic lanthanides metal complexes for photodynamic therapy

New Schiff base ligand: 4-methoxy salicaldhyde-2-2-phenyl-hydrazono acetaldehíyde prepared by facile method. The molecular structures characterized by elemental analysis and proton magnetic resonance spectra (1H-NMR spectra). This spectra at the chemical shifts (3.5–10.39 ppm) confirmed the types and the numbers of protons. The sharp melting point at the range 110–112 °C confirmed purity. New optically active metal (samarium, terbium and gadolinium) complexes of the Schiff base synthesized in a one pot reaction. Vibrational IR spectra confirmed functional groups. Scanning electron microscopy micrographs confirmed that the modified microstructure of the metal complexes differed in morphology than the ligand. Powder X-ray diffraction patterns confirmed good crystalline structure. The optically activity of the solid metal complexes confirmed from electronic absorption spectra. The UV absorbance band at the wavelength range 280–390 nm and the intense phosphorescence bands up to 830 nm enabled application in photo dynamic therapy for apoptosis cancer cells by conversion triplet oxygen in the tissues into reactive singlet oxygen. Low charge transfer energy: 2.59–2.61 eV, high molar extinction coefficients (ε) at the order of magnitude \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{10}^{6}$$\\end{document} M− 1 cm− 1 and the intense phosphorescence bands reflected good photodynamic activity. The metal complexes are thermally stable.

Molecular Engineering of membrane structure targeted photosensitizers for antitumor photodynamic therapy

Photodynamic therapy (PDT) has been used to cure special diseases or the diseases that localized at special sites in comparison with conventional therapy, due to its high spatiotemporal selectivity, non-invasion, low drug resistance. However, vast majority of photosensitizers (PSs) still suffer from several limitations including poor aqueous solubility and poor photostability. Here, we used two strategies, promoting the intramolecular charge transfer and terminal modification, to overcome these limitations and enhance therapeutic effects. Three membrane-structure targeted molecules, 3CN-Np, 3CN–OH, and 3CN-QA, were designed and synthesized, which exhibited high extinction coefficient, excellent photostability and reactive oxygen species (ROS) productive capacity. In cell imaging, the designing molecules would stain endoplasmic reticulum for 3CN-Np and 3CN–OH, and cell membrane for 3CN-QA, respectively. Afterwards, we used white light (25 mW/cm2) to irradiate the probe cultured cells for 20 min, the ratio of the dead and live cells was 3.0 for 3CN-Np, 3.5 for 3CN–OH, and 3.7 for 3CN-QA. Based on the high cell apoptosis in vitro under a white-light, 3CN–OH was selected to inhibited tumor growth in vivo, and the tumor volume was reduced to 45 % with non-toxicity to vitals. The study provided new sights in developing PSs with high water-solubility, photostability, and ROS generating ability in white-light mediating PDT system.

Rational design and synthesis of pyrrolo-pyridine dinitrile dyes with strong dual-state emission

In recent years, there has been a growing focus on organic dual-state emission (DSE) materials that demonstrate robust luminescence in both solid and solution states. Nevertheless, in the solid state, π-π stacking between organic molecules often results in pronounced luminescence quenching, posing a significant challenge for the design and synthesis of organic DSE materials. In this work, a pyrrolo-pyridine dinitrile (PPDN) dye was synthesized from commercially available 2-heteroaryl acetonitriles and classical diketopyrrolopyrrole (DPP) dye via a two-step process. Due to its special "J"-shaped planar conjugate structure, the PPDN dye has strong DSE performance, high molar extinction coefficients (ε), large Stokes shifts, and excellent optical and thermal stability. It also has aniline vision detection capability, which is useful in the field of security displays and anti-counterfeiting.

Reengineering of Donor-Acceptor-Donor Structured Near-Infrared II Aggregation-Induced Emission Luminogens for Starving-Photothermal Antitumor and Inhibition of Lung Metastasis.

Electron acceptor possessing strong electron-withdrawing ability and exceptional stability is crucial for developing donor-acceptor-donor (D-A-D) structured aggregation-induced emission luminogens (AIEgens) with second near-infrared (NIR-II) emission. Although 6,7-diphenyl-[1,2,5] thiadiazolo [3,4-g] quinoxaline (PTQ) and benzobisthiadiazole (BBT) are widely employed as NIR-II building blocks, they still suffer from limited electron-withdrawing capacity or inadequate chemo-stability under alkaline conditions. Herein, a boron difluoride formazanate (BFF) acceptor is utilized to construct NIR-II AIEgen, which exhibits a better overall performance in terms of NIR-II emission and chemo-stability compared to the PTQ- and BBT-derived fluorophores. With finely tuned intramolecular motions and strong D-A interaction strength, TPE-BFF simultaneously exhibits high molar extinction coefficient (ε= 4.31 × 104 M-1cm-1), strong NIR-II emission (Φ = 0.49%) and photothermal effect (η = 58.5%), as well as high stability. Thanks to these merits, the thermosensitive nanoparticles constructed by integrating TPE-BFF and the antiglycolytic agent 2-deoxy-d-glucose (2DG) are successfully utilized for imaging-guided photothermal antitumor lung metastasis by regulating glycolysis and reducing ATP-dependent heat shock proteins. Combining experimental results and theoretical calculations, BFF proves to be an outstanding electron acceptor for the design of versatile NIR-II AIEgens. Overall, this study offers a promising alternative for developing multifunctional NIR-II AIEgens in biomedical applications.

Elucidating the Supramolecular Interaction of Positively Supercharged Fluorescent Protein with Anionic Phthalocyanines.

Developing bioinspired materials to convert sunlight into electricity efficiently is paramount for sustainable energy production. Fluorescent proteins are promising candidates as photoactive materials due to their high fluorescence quantum yield and absorption extinction coefficients in aqueous media. However, developing artificial bioinspired photosynthetic systems requires a detailed understanding of molecular interactions and energy transfer mechanisms in the required operating conditions. Here, the supramolecular self-assembly and photophysical properties of fluorescent proteins complexed with organic dyes are investigated in aqueous media. Supercharged mGreenLantern protein, mutated to have a charge of +22, is complexed together with anionic zinc phthalocyanines having 4 or 16 carboxylate groups. The structural characterization reveals a strong electrostatic interaction between the moieties, accompanied by partial conformational distortion of the protein structure, yet without compromising the mGreenLantern chromophore integrity as suggested by the lack of emission features related to the neutral form of the chromophore. The self-assembled biohybrid shows a total quenching of protein fluorescence, in favor of an energy transfer process from the protein to the phthalocyanine, as demonstrated by fluorescence lifetime and ultrafast transient absorption measurements. These results provide insight into the rich photophysics of fluorescent protein-dye complexes, anticipating their applicability as water-based photoactive materials.

Competitiveness of chia against brassica weeds improves through a narrow spatial arrangement

Chia (Salvia hispanica L.) is a promising crop valued as a sustainable source of omega-3. However, chia yield and quality are reduced because of weed competition and the lack of registered herbicides. This study evaluated how chia spatial arrangement suppresses weed growth and provided management options for this crop. The performance of chia plants was assessed over three growing seasons in field experiments using a factorial design that considered spatial arrangement (narrow and wide), weed management (control without weeds, soil bank brassica (Brassica rapa L.), and sown brassica), and cover crop (with or without a rye (Secale cereale L.) cover crop during chia fallow). Chia and brassica are not complementary, leading to resource competition (relative yield total around 1) and negative effects on each other. A significant decrease in chia grain yield of 0.9% per unit increase in the percentage of weeds in total biomass was observed. As chia had a competitive advantage over brassica, the grain yield reduction was ameliorated with a narrow spatial arrangement. Narrow spatial arrangement promotes faster canopy closure during the early growth stages, decreasing light penetration and suppressing weed growth. The high extinction coefficient of chia (0.91) and the low critical LAI (3.3) contributed to this light interception behavior. Accordingly, to maximize chia productivity and profitability, a narrow spatial arrangement is an effective management strategy to suppress weeds. This study contributes valuable insights into chia-weed interactions and emphasizes the importance of sustainable crop management practices.

A NIR-II Organic Dendrimer with Superb Photothermal Performance Based on Electron-Donor Iteration for Photothermal Immunotherapy.

Organic photothermal materials have attracted extensive attention due to their designable molecular structure, tunable excited-state properties, and excellent biocompatibility, however, the development of near-infrared II (NIR-II) absorbingorganic photothermal materials with high photothermal conversion efficiency (PTCE) and molar extinction coefficient (ɛ) remains challenging. Herein, a novel "electron-donor iteration" strategy is proposed to construct organic photothermal dendrimers (CR-DPA-T, CR-(DPA)2-T and CR-(DPA)3-T) with donor-π-acceptor-π-donor (D-π-A-π-D) features and diradical characteristics. Owing to the enhanced D-A effect and intramolecular motions, their absorption and photothermal capacity increase as the generation grows. Surprisingly, an excellent photothermal performance (ɛ1064 ×PTCE1064) with a superb value of 2.85×104 in the NIR-II region is achieved for CR-(DPA)3-T nanoparticles (CR-(DPA)3-T NPs) compared to most reported counterparts. Besides, CR-(DPA)3-T NPs exhibit superior antitumor efficacy by the synergistic effect of photothermal therapy (PTT)and immunotherapy, efficiently inhibiting the growth of both primary and distant tumors. To the best knowledge, organic photothermal dendrimer is for the first time reported, and a universal donor engineering strategy is offered to develop NIR-II-absorbing organic photothermal materials for photothermal immunotherapy.

Ternary Ag3AuS2 Nanocrystals for Thin-Film Solar Cells.

The concept of clean and pollution-free energy development has promoted the rise of environmentally friendly silver-based chalcogenide nanocrystal (NC) solar cells, but currently reported silver-based NCs need complex synthesis processes at high temperatures that may bring zerovalent noble metal impurities for their high redox potentials. In this study, we report a facile synthesis of novel Ag3AuS2 NCs by injecting highly active oleylamine sulfur complexes as sulfur sources into metal precursor solutions at low temperatures of 60 °C. The obtained Ag3AuS2 NCs exhibit broad absorption spectra and high molar extinction coefficients (106 M-1 cm-1). Then, the Ag3AuS2 NCs are applied as the light-absorbing active layer in environmentally friendly thin-film solar cells. By introducing a hybrid mixture of charge acceptors and donors (NCs/P3HT hybrid film) at the interface, the device gains an absorption increment and enhanced charge extraction, achieving a final power conversion efficiency of 3.38%. This work demonstrates the enormous potential of Ag3AuS2 NCs from low-temperature preparation for photovoltaic applications.

Direct comparison of colorimetric signal amplification techniques in lateral flow immunoassays.

The lateral flow immunoassay (LFIA) is widely adopted for point-of-care testing, but its limit of detection (LoD) falls short of that of laboratory-based immunoassays. Several techniques have been proposed to enhance the LoD of LFIAs using visual colorimetric readouts, yet a direct comparison of the LoDs achieved by these techniques has not been performed. In this work, we measure the LoDs of LFIAs designed for the detection of a malaria protein, PfHRP2, using four different colorimetric signal generation techniques: (i) AuNP(40 nm)-tagged detection antibodies (base case), (ii) AuNP-based enhancement of AuNP(40 nm) signal, (iii) oxidation of chloronaphthol/diaminobenzidine (CN/DAB) using HRP-tagged detection antibodies, and (iv) oxidation of CN/DAB using polyHRP(400)-tagged detection antibodies. The LoDs and the 95% confidence intervals of the LoDs achieved by the 4 techniques were 19.34 (13.37-27.62) ng mL-1, 9.57 (6.76-13.28) ng mL-1, 21.57 (14.26-32.18) ng mL-1, and 6.09 (2.23-13.47) ng mL-1, respectively. Contrary to popular perception, enzymatic signal generation using HRP-tagged detection antibodies did not improve the LoD compared to the base case of AuNP-based signal generation. Further studies revealed that the very high extinction coefficient of gold nanoparticles renders them an excellent choice for colorimetric detection, surpassing the performance of enzymatic signal generation using HRP-tagged antibodies. However, enzymatic signal generation using polyHRP-tagged antibodies improved the LoD compared to the base case. These results show that enzymatic signal amplification should not be a priori assumed to be superior to AuNP-based signal generation; and provide a reference point to LFIA developers to select an appropriate signal generation modality.

Flame stabilization and emission reduction: a comprehensive study on the influence of swirl velocity in hydrogen fuel-based burner design

PurposeThis study aims to numerically analyse a full-scale burner across a wide range of operating pressure conditions and determine the effect of swirl velocity on flame stabilization, flame holding and combustion performance.Design/methodology/approachThis study uses a numerical analysis approach to investigate a three-dimensional full-scale burner. Modified governing equations are used to determine the effect of swirl velocity on flame stabilization and flame holding. The GR-Mech 3.0 chemical reaction mechanism is used to predict the combustion process. To validate the model, a grid independence study is performed.FindingsThe study reveals that swirl velocity enhances flame stability, resulting in better combustion rates. As the swirl velocity increases, higher flame temperatures are observed due to high convective heat recirculation. The heat transfer coefficient and high radiative extinction coefficient are found to vary based on fuel swirl velocity. The mass fraction of CH4 and CO emphasizes the role of swirl velocity on flame structure. Increasing velocity potentially improves combustion by delaying the process, leading to better combustion and lower emissions.Originality/valueThe findings of this study contribute to the understanding of swirl-stabilized combustion and can guide the development of advanced combustion technologies, making it a valuable addition to the existing combustion field.

A glutathione responsive photosensitizer based on hypocrellin B for photodynamic therapy

As a typical natural photosensitizer, hypocrellin B (HB) offers the advantages of high molar extinction coefficient, high phototoxicity, low dark toxicity, and fast metabolism in vivo. However, the lack of tumor specificity hinders its clinical applications. Herein, we designed and synthesized a glutathione (GSH) responsive photosensitizer based on HB. The 7 − nitro − 2,1,3 − benzoxadiazole (NBD) covalently connected to HB not only served as a fluorescence quenching group but also as a GSH activating group. The photosensitizer HB−NBD showed almost no fluorescence and singlet oxygen generation as a result of the photoinduced electron transfer between HB and NBD. The designed photosensitizer HB−NBD can be activated by GSH in solutions and cancer cells, and then obtain recuperative fluorescence and photosensitive activity.

Effect of electron-donating and -withdrawing substitutions in naphthoquinone sensitizers: The structure engineering of dyes for DSSCs in Quantum Chemical Study

Dye-sensitized solar cells (DSSCs) are cost-effective photovoltaic devices that convert solar energy into electricity using a dye sensitizer, TiO2 photoanode, electrolyte, and counter electrode. This study investigates the impact of substituents on the performance of naphthoquinone-based dye sensitizers in DSSCs. We analyzed various naphthoquinone derivatives’ electronic structures and light absorption properties using DFT and TD-DFT. Our results demonstrate that electron-donating groups enhance DSSC performance by improving light absorption and electron injection. Specifically, naphthoquinone derivatives with methoxy (Dye-2) and methyl (Dye-3) groups showed superior properties. TD-DFT analysis revealed high molar extinction coefficients over a broad spectrum, making these dyes efficient at capturing sunlight. Additionally, these dyes effectively interact with TiO2, which is crucial for photostability and photovoltaic performance. In conclusion, naphthoquinone derivatives with electron-donating groups significantly improve DSSC performance, with Dye-2 and Dye-3 being strong candidates for high-performance applications.

Palladium catalyzed carbon-carbon bond formation on tunable quinolines with DFT study

The synthesis of new quinoline fluorophores was accomplished through a meticulous four-step molecular assembly utilizing Suzuki and acid-amine cross-coupling reactions. The integrity of each fluorophore was rigorously confirmed via comprehensive spectroscopic analyses, including 1H and 13C NMR, DEPT-135, H-H COSY, HSQC NMR and HRMS techniques. Subsequently, the absorbance and emission spectra of the newly synthesized fluorophores were thoroughly investigated. Notably, these fluorophores displayed impressive characteristics, with high intensity and significant molar extinction coefficients, along with Stokes shifts ranging from 0.5052 × 104 to 0.6234 × 104 in acetonitrile (ACN) solvent. Absorbance spectra were found to confine within the 320–360 nm range, while emission spectra were consistently observed within the 380–450 nm range upon excitation at 350 nm. The electronic structure of the molecules was elucidated using techniques such as Density Functional Theory (DFT) and Molecular Electrostatic Potential (MEP) mapping. Additionally, the calculated global reactivity parameters provided valuable insights. In particular, compound 8b exhibited a distinctly larger energy gap compared to other fluorophores, demonstrating its exceptional properties. The comparison between experimental and theoretical UV-Vis spectra also showcased the remarkable consistency and quality of the synthesized fluorophores, highlighting the significant potential of this work in the field of fluorophore development.

Performance enhancement of dye solar cell using mixed synthetic organic dyes

The potential of dyes derived from Bromophenol and Rhodamine, both as single and mixed dyes, in dye-sensitized solar cells (DSSCs) to achieve panchromatic light harvesting and enhance cell performance is assessed in this study. The study finds that a high molar extinction coefficient caused by the combined properties of the dyes matched with the spectrum area where the novel sensitizers deficit light-harvesting, indicating effective co-sensitization. To ascertain the dyes' characteristics and appropriateness as sensitizers, a variety of methods, including cyclic voltammetry, UV–Vis spectroscopy, and Fourier-transform infrared spectroscopy (FTIR), are used. Cyclic voltammetry results indicate that the dyes under study exhibit excellent redox stability and sufficient thermodynamic dynamic force for efficient electron introduction. According to the photovoltaic performance statistics, the mixed dye of Rhodamine and Bromophenol based cell had the maximum efficiency (η) and power (Jsc) are 4.06 mA and 1.29 %, respectively. This is made feasible by photosensitive light-harvesting, remarkable visual activity, and sufficient energy levels. Acidified mixed dyes were more able to load on the TiO2 surface due to their homogenous dispersion, reduced steric barriers, and multi-anchor group connected to the semiconductor surface. With such novel mixed dye, it is expected that the mixed dye with not only high efficiency but higher Jsc value will be an alternative to single dyed based DSSCs.

Fabrication of dye-sensitised solar cell using dry Ixora extract as sensitiser

ABSTRACT A dye-sensitised solar cell was fabricated using dry Ixora flower extract. The sensitiser was obtained by physical extraction using a mixture of ethanol and distilled water as solvent in the ratio of 7:3. The optical study of the sample was done within wavelength range of 230 nm to 1100 nm using spectrophotometer (UV- 750 series). The outcome shows an optimum absorption in the visible region of the EM spectrum, which shifted to the UV region when adsorbed onto a nano-porous TiO2 surface. An alternative peak of 0.95a.u in the visible region was observed with enhanced optical absorption across the infrared region of the spectrum. The absorption coefficient values suggest the extract absorbs light in the visible region, which was also confirmed with the relatively high extinction coefficient observed in the visible region of the EM spectrum. The extract exhibits a low transmittance in the visible range, which increases to over 99% in the red wavelengths. The extract has low reflectance of about 20% in the visible range, which falls lower as wavelength increases into the infrared region. The energy band gap (for direct transition) of 2.13 eV was obtained for dry Ixora dye extract. The fabricated solar cell performed a fill factor of 0.27, Jsc of 0.1273 mA/cm2, Voc of 0.7001 V, and conversion efficiency of about 0.02%. with these results, the dye extract of dry ixora flower can serve as a good photo-sensitiser for the fabrication of dye-sensitised solar cell.

(Invited) Reshaping Light with Hybrid Quantum Dot: Molecule Systems

Photon upconversion is an energy conversion process wherein a material absorbs two or more low-energy photons and uses their energy to generate high-energy photons. Upconversion systems that convert near-infrared light into the visible range can address current challenges in solar energy capture and near-infrared sensor design while materials that operate at higher energy, producing UV photons from visible light, can enable applications in photocatalysis and light-based 3D printing. Due to their high extinction coefficients and size-tunable optical properties, quantum dots have emerged as ideal photosensitizers for photon upconversion systems. In these systems, light absorbed by a quantum dot is passed to a molecule at its surface, placing the molecule into a spin-triplet state. Upconversion is achieved when two molecules in their triplet state encounter one another and undergo triplet fusion, a process that deexcites one molecule and promotes the other to a high-energy, emissive spin-singlet state. In this presentation, I will present spectroscopic measurements and electronic structure calculations that identify energy transfer rates and key intermediates involved in two quantum dot systems that respectively demonstrate red-to-blue and blue-to-UV photon upconversion. In the first system, which consists of silicon quantum dots functionalized with anthracene ligands, we find that by controlling the chemical structure of molecular tethers that covalently link anthracene to silicon, we can produce strongly coupled states wherein excited charge carriers are shared between silicon and anthracene. By controlling the energy of these states, we can optimize the system’s performance, achieving an upconversion quantum yield of 17.2%. In the second system, we use CsPbBr3 perovskite quantum dots to drive triplet energy transfer to naphthalene ligands. This energy transfer process is found to be highly sensitive to the structure of the chemical linker that binds naphthalene to CsPbBr3, which we attribute to modulation of the degree of wavefunction overlap between the states of the quantum dot energy donor and naphthalene energy acceptor.

Synthesis, Electrochemistry and Photochemistry of Hypervalent Phosphorus(V) Porphyrin and Antimony(V) Porphyrin Black Dyes

In the last few years, our focus has been on push-pull type hypervalent Group 15 porphyrins with intramolecular charge transfer (ICT) properties. Insertion of P(V) or Sb(V) ion in the porphyrin cavity results in a highly electron-deficient porphyrin center, under this condition the presence of electron-rich units in porphyrin meso-positions results in charge transfer within the molecules. Recently, we extended this strategy to 5,10,5,20-tetrakis(triphenylamine)porphyrin derivative where strong electron donor triphenylamine (TPA) units are in meso-positions. Upon insertion of the P(+5) and Sb(+5) ion, the resulting hypervalent Group 15 porphyrins manifested a strong ICT from the TPA units to the central porphyrin ring. The existence of ICT makes the absorption profiles cover the entire visible region with high molar extinction coefficients. Due to this reason, the studied hypervalent Group 15 porphyrins appear as black dyes. Here, I will present these porphyrins and discuss their structural, redox, and remarkable photophysical properties. Figure 1

Improving Photophysical Properties and Hydrophily of Conjugated Polymers Simultaneously by Side-Chain Modification for Near-Infrared Cell Imaging.

Conjugated polymers (CPs)-based near-infrared phototheranostics are receiving increasing attention due to their high molar extinction coefficient, wide emission wavelength, easy preparation and excellent biocompatibility. Herein, several new conjugated polymers with D2-D1-A structures were easily prepared through one-pot coupling using triphenylamine (D2) as well as thiophenes (D1) as electron donors and benzothiadiazole (A) as electron acceptors. Interesting, their optical performance and power conversion efficiency could be tuned by side chains on thiophenes (D1). The introduction of ethylenedioxy into D1 as side chain significantly improves fluorescence imaging brightness, photothermal conversion efficiency and hydrophilicity, and extends emission wavelength, which are beneficial for phototheranostic. The side chain modification provides new opportunity to design efficient phototheranostics without construction new fluorescent skeletons.

Emission-based sensing of cobalt (II) and vitamin B12 via a bis-indole derivative.

In this study, a bis-indole compound was synthesized, characterized by 1H NMR, Fourier transform infrared, and mass spectroscopic measurements and used as a selective and efficient probe for the spectrofluorimetric analysis of Co (II). The cobalt-induced quenching in the emission maximum at 567 nm was considered as the analytical signal in calibration studies. When encapsulated in a polymethyl methacrylate (PMMA) matrix, the bis-indole compound exhibited a limit of detection (LOD) of 3.60 × 10-11 M for Co (II). Vitamin B12, which contains a cobalt ion in the center of a corrin ring in its structure, was also successfully quantified using the same probe. The bis-indole compound showed a linear response based on quenching for increasing concentrations of vitamin B12, partially mimicking the contracted tetrapyrrole ring found naturally in the center of vitamin B12. The LOD for vitamin B12 was found to be 76 nm. Promising photophysical properties of the proposed probe, including high molar extinction coefficient, considerable quantum yield (0.46 and 0.64 in tetrahydrofuran and PMMA, respectively), high Stoke's shift and satisfactory photostability, make it a good choice for fluorescence-based Co (II) determination. The ML3-type stoichiometry of the complex between the dye and cobalt was elucidated both by Job's method and by high-resolution mass spectrometry (HR-MS).