Photophysical Characterization Research Articles

Lasing properties, Judd-Ofelt and band gap investigation of cool green emanating Tb3+ complexes for solid and solution state luminescence

Optical and photophysical characteristics of six green emanating terbium complexes which have been prepared by eco-efficient solvent assisted grinding process. The prepared complexes display bright green luminescence with a prominent peak at 548 nm accredited to 5D4 → 7F5 transition of terbium ions, as examined by PL emission spectra monitored at 355 nm excitation wavelength. Spectroscopic investigation of these synthesised complexes was explored. Photometric features such as CIE coordinate, CCT and %CP asserted their green luminescence and are found in agreement with brilliant green light. Lasing properties, optoelectronic and thermal analysis of terbium complexes were performed. To determine the coordination environment around the metal ion, JO parameter (Ω2, Ω4, Ω6) and intensity ratio were also determined. The research offers a glowing cool green emitting constituent for the manufacturing of OLEDs and innovative optoelectronic devices. Antioxidant and antimicrobial properties were also examined. Computational studied of complexes were carried out successfully.

Preparation, characterization and spectroscopic analyses of Dy(III) β-diketonates with bidentate N donor neutral ligands for displays

A group of octa-coordinated, anhydrous in nature luminous compounds whose general formula is [Dy(DPD)3L] where ‘DPD’ denotes 1,3-diphenylprop-1,3-dione and ‘L’ corresponds to 2,2ʹ-bipyridine and its derivatives, has been synthesised and fully characterized by CHN, FTIR, NMR and thermal analyses. Dysprosium ion is chelated with ‘O’ atoms of three bidentate β-diketones and ‘N’ atoms of one bidentate neutral ligand. The NMR spectra of synthesised complexes revealed that the protons of β-diketone and –N donor ligands are shifted in opposite direction due to paramagnetic character of Dy(III) ion. Photophysical and electrochemical characteristics of synthesized complexes were studied by absorption, photoluminescence and cyclic voltammetry techniques. The PL spectra of dysprosium ion generate its characteristic yellow emission due to the hyper intense transition i.e.,4F9/2 → 6H13/2 which is sensitive to the bonding environment of trivalent ion. The optical band gap data and branching ratio (4F9/2 → 6H13/2) confirms the effectiveness of synthesized complexes in displays and magnets.

Solution-State Studies, X-ray Structure Determination and Luminescence Properties of an Ag(I) Heteroleptic Complex Containing 2,9-Bis(styryl)-1,10-phenanthroline Derivative and Triphenylphosphine

A novel heteroleptic Ag(I) compound, formulated as [AgL(PPh3)]BF4 (1) (where L represents 2,9-bis((E)-4-methoxystyryl)-1,10-phenanthroline and PPh3 stands for triphenylphosphine), was successfully synthesized and thoroughly characterized. The compound’s stability in solution was confirmed through 1D and 2D nuclear magnetic resonance (NMR). The photo-irradiation of the complex in a CDCl3 solution, utilizing a common portable UV lamp emitting at λ = 365 nm, led to the partial transformation of the E,E-geometric isomer to E,Z, ultimately yielding a 1:1.4 molar ratio of isomers. Its molecular structure was determined via X-ray crystallography, while molecular packing was assessed using Hirshfeld calculations. The most notable interactions (51%) within the cationic inner sphere involved H···H bonds. The photophysical characteristics of the complex and L were evaluated both in the solid state and in solution (dichloromethane). Compound 1 is a weak emitter, with photoluminescence quantum yields of 8.6% and 4.3% in solution and the solid state, respectively.

Theoretical analysis on D-π-A dye molecules with different acceptors and terminal branches for highly efficient dye-sensitized solar cells

Triphenylamine and 9-phenylcarbazole are the most common electron donor groups, now based on the two groups, eight D-π-A dyes are designed as sensitizers for dye-sensitized solar cells (DSSCs).The eight dyes use the same π-conjugated bridge (thiophene moiety and carbon-carbon double bond) and acceptor fragment (cyanoacrylic acid), and the donor group is added with additional electron-D groups to the original triphenylamine and 9-phenylcarbazole (C4H9 alkyl chain, C4F9 perfluoroalkyl chain, and methoxy), and comparing the properties of several donor groups and terminal branched chains while ensuring that the π-bridges and acceptors are identical. The photophysical properties, electronically excited states, and chemical reactivity affecting the performed dyes have been determined with DFT and TD-DFT calculations of bond lengths and dihedral angles between fragments, frontier molecular orbitals, density of states, isosurface molecular electrostatic potential, charge density differences, fragment transition density matrix, UV–Vis absorption spectra, quantum chemical, and photovoltaic parameters. Comparisons have been made between the dyes under study's photophysical characteristics, electrically excited states, and chemical reactivity. Among all the different donor dyes designed, SH-3 and ZD-3 are poorly molecularly planar compared to the same series of molecules with parameters such as large HOMO-LUMO energy gaps (2.78 eV, 3.28 eV), maximum excited energies (2.93 eV, 3.13 eV), and the shortest absorption peaks (422.76 nm, 396.48 nm), which are considered to be the worst material for photovoltaic applications. Whereas, SH-4 and ZD-4 have the smallest energy gap values (2.35 eV, 2.74 eV) and vertical excitation energies (2.66 eV, 3.04 eV) as well as having the longest absorption peaks (465.34 nm, 408.42 nm), the largest open circuit voltages (1.42 eV, 1.34 eV), which are the best designs among the two groups of molecules. The rest of the designed organic dyes have suitable photophysical properties and all of them are highly recommended for DSSCs.

Preparation of Carbazoles Involving 6π-Electrocyclization, Photoredox-, Electrochemical-, and Thermal Cyclization Reactions: Mechanistic Insights.

Carbazole is a heterocyclic motif that can be found in a diverse array of natural and unnatural products displaying a wide range of biological and physiological properties. Furthermore, this heterocycle is part of electronic materials like photoconducting polymers and organic optoelectronic materials owing to its excellent photophysical characteristics. Consequently, the development of synthetic strategies for carbazole scaffolds holds potential significance in biological and material fields. In this regard, a variety of preparation methods has been developed to exploit their efficient and distinct formation of new C-C and C-heteroatom bonds under mild conditions and enabling broad substrate diversity and functional group tolerance. Therefore, this review focuses on the synthesis of a set of carbazole derivatives describing a variety of methodologies that involve direct irradiation, photosensitization, photoredox, electrochemical and thermal cyclization reactions.

BODIPY-Based Molecules for Biomedical Applications.

BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) derivatives have attracted attention as probes in applications like imaging and sensing due to their unique properties like (1) strong absorption and emission in the visible and near-infrared regions of the electromagnetic spectrum, (2) strong fluorescence and (3) supreme photostability. They have also been employed in areas like photodynamic therapy. Over the last decade, BODIPY-based molecules have even emerged as candidates for cancer treatments. Cancer remains a significant health issue world-wide, necessitating a continuing search for novel therapeutic options. BODIPY is a flexible fluorophore with distinct photophysical characteristics and is a fascinating drug development platform. This review provides a comprehensive overview of the most recent breakthroughs in BODIPY-based small molecules for cancer or disease detection and therapy, including their functional potential.

The Effect of Monodentate Co-Ligands on the Properties of Pt(II) Complexes Bearing a Tridentate C^N*N-Luminophore

In this study, the insertion of different monodentate co-ligands on Pt(II) complexes bearing a monoanionic C^N*N luminophore as a tridentate chelator was achieved beyond the previously reported chlorido- ([PtCl(L)]) and cyanido-decorated ([PtCN(L)]) analogues. To investigate the impact of the auxiliary ligand on the photophysical properties, we introduced a neutral carbonyl-ligand and observed a lower photoluminescence quantum yield (ΦL) than with a cyanido moiety. However, the direct substitution of the chlorido co-ligand by a NO-related derivative was not successful. Interestingly, the attempted reduction of the successfully inserted nitrito-N-ligand in [PtNO2(L)] resulted in the oxidation of the Pt(II)-center to Pt(IV), as demonstrated by X-ray diffractometry. For comparison, the trifluoroacetato Pt(II) and chlorido Pt(IV) complexes ([PtTFA(L)] and [PtCl3(L)], respectively) were also synthesized. The photophysical characterization revealed similar photoluminescence profiles for all complexes, indicating a weak effect of the co-ligand on the excited state; in fact, all complexes display emission from metal-perturbed ligand-centered states (even the Pt(IV) species). Nonetheless, longer excited state lifetimes (τav) suggest a reduced thermally-activated radiationless deactivation via metal-centered states upon exchange of the chlorido units for other monodentate entities, yet without significantly improving the overall ΦL at room temperature. The irreversible oxidation waves (measured via cyclic voltammetry) mostly stem from the Pt(II)-center; the co-ligand-related drop of these potentials correlates with the increasing σ-donating capacities of the ancillary ligand. In summary, an enhanced π-acceptor capacity does not necessarily improve the ΦL and can even impair radiative rates by compromising the perturbative participation of the metal center on the emissive triplet state; in addition, strong σ-donor abilities improve the phosphorescence efficiencies by hampering the thermal population of dissociative electronic configurations related to the participation of antibonding d*-orbitals at the metal center.

A novel bis(β-Br-BODIPY) photosensitizer and its nanoscale delivery systems based on polymer micelles and zeolite-like MOFs

The design of biocompatible photosensitizers with an optimal combination of intense fluorescence and generation of singlet oxygen is a complex and urgent task. The article presents the results of synthesizing, analyzing the structure, and examining the chromophoric, fluorescent, and generation characteristics of new dimeric bis(β-Br-BODIPY) (1), as well as the features of its encapsulation in ZIF-8 zeolite framework and solubilization by Pluronic® F127 micelles. The photophysical characteristics of brominated dimer 1 were analyzed in comparison with non-halogenated dimers bis(β-H-BODIPY) (2), bis(β-CH3-BODIPY) (3), as well as dibromo-substituted mononuclear analogue β,β-dibromo-BODIPY (4). Dye 1 exhibits efficient fluorescence (from 53 to 72%) and 1O2 generation (from 19 to 42%) in solutions of nonpolar and weakly polar solvents. Dimerization leads to a high sensitivity of the fluorescence and generation characteristics of the halogenated dimer 1 to the solvent. The advantage of dimer 1 is a significantly lower tendency to aggregate compared to monomer 4. The conditions for the encapsulation of dye 1 in ZIF-8 nanoparticles and Pluronic® F127 micelles were determined and their structural and spectral characteristics were analyzed.

Design, synthesis, and evaluation of 5,15-diaryltetranaphtho [2,3]porphyrins as photosensitizers in real-time photodynamic therapy and photodiagnosis

In the pursuit of new potent photosensitizers (PSs) for photodynamic therapy (PDT) with better efficacy, a series of 5,15-diaryltetranaphtho [2,3]porphyrins (Ar2TNPs) with two or four carboxyalkoxy groups were designed, synthesized, and evaluated. These new compounds exhibited strong, broad and red-shifted UV–vis absorptions at 729 nm and other strong absorptions at 446, 475, 650, 659, 714 nm for tumors and other diseases of varying sizes and depths. They possess high molar extinction coefficients (0.95 × 105–1.48 × 105 M−1 cm−1), good singlet oxygen quantum yields and photodynamic antitumor effects towards Eca-109 cells in vitro. It is suggested that the extension of porphyrin with naphthalene into Ar2TNP results into remarkable improvement of photophysical characteristics, while the introduction of carboxyalkoxy groups on meso-phenyl can significantly improve the solubility and photodynamic effects in vitro and in vivo. Notably, compound II3 can localize primarily in lysosomes of Eca-109 cells and induce substantial cell apoptosis after PDT. It can also selectively accumulate in tumor tissues and be traced real-timely through in vivo fluorescence imaging with distinctive inhibition of tumor growth. Therefore, compound II3 deserves to be considered as a promising PDT drug candidate for individualized tumor real-time tracing and treatment.

A shining transmutation of lignin into multicolor carbon dots via the dynamic solvent-fractionation engineering

As a fascinating luminescent subclass, the rapid growth of versatile carbon dots from ideally sustainable biomass has been shouldering the duty of relieving energy and environment pressures that is committed to carbon neutrality. Despite the renewable lignin with conjugated aromatic structure, tunable linkages and functional species (e.g.,–OH, –COOH and –OCH3), the fabrication of multicolor lignin-derived carbon dots (LCDs) covering the red-emissive luminescence is awkward by lacking the task-specific techniques and modulating mechanisms. Herein, a library of blue, green and red-emissive LCDs is built through a stepwise solvent-fractionation engineering with dynamic ethanol sieving and dichloromethane/water extraction. By refined lignin, it is revealed that their average molecular weights and –OH/COOH contents dominate the nanosize, reactivity, lifetime, and photophysical features of LCDs. We then showcase the gradient lignin structure to involve LCDs properties capable of driving their potential functions in the multi-target sensing and solid-state luminescent films. Monitoring tetracycline and metal-ions (Fe3+, Al3+ and/or Ag+) with the ideal selectivity and sensitivity within a broad concentration is accomplished via evaluating the linear correlations. Transparent solid-state luminescent composite films that demonstrate the promising scalability of reserving perishable fruit are successfully prepared using red-emitting LCDs as additives in polyvinyl alcohol matrix. Hence the in-depth understanding of lignin chemistry will provide a technical guidance to achieving multicolor LCDs with tailored fluorescence performances and functionalities.

Fluorinated derivatives of 2-azinyl-4-(4-aminophenyl)quinazolines: Synthesis and photophysical properties

Herein, we present design, synthesis and photophysical properties of fluorinated 2-pyridyl and 2-pyrimidinylquinazolines bearing electron donating aminoaryl moiety at the position 4. The described compounds are synthesized in three steps starting from 2-cyanoazine and fluorinated anthranilic acid. The structures of the target compounds are confirmed by NMR spectroscopy, mass spectrometry as well as X-ray diffraction analysis. The photophysical characteristics are investigated in toluene and MeCN. In case of Et2N- and Ph2N-derivatives the quantum yields increase when going from MeCN to toluene and reach 87 %, whereas emission intensity of carbazolyl counterparts reduces with the decrease in solvent polarity. All the compounds exhibit considerable sensitivity to solvent polarity and change their emission color from blue to red–orange. Additionally, the 2,4-disubstituted fluorophores display two-photon absorption in MeCN with δ2PA in the range of 18.9–227.8 GM.

Revealing the Origin of Fast Delayed Fluorescence in a Donor Functionalized Bisterpyridine.

A new carbazole-substituted bisterpyridine with pronounced delayed fluorescence is presented. While the molecular donor-acceptor-donor design suggests the origin of this to be thermally activated delayed fluorescence (TADF), results from various photophysical characterizations, OLED characteristics, temperature-dependent NMR spectroscopy, and DFT calculations all point against the involvement of triplet states. The molecule exhibits blue emission at about 440 nm with two or more fast decay channels in the lower nanosecond range in both solution and thin films. The delayed emission is proposed to be caused by rotational vibrational modes. We suggest that these results are generally applicable, especially for more complex molecules, and should be considered as alternative or competitive emissive relaxation pathways in the field of organic light emitting materials.

Antibacterial photodynamic inactivation with elicited Andrographis paniculata (Burm. f.) Wall. ex Nees plant extract derived carbonaceous nanoparticle

BackgroundConversion of phytoproducts into nanoparticles for antimicrobial intervention is common but employing elicitation to the plant to achieve dual and more potent chemical and photodynamic effects is seldom researched or achieved. PurposeAntimicrobial photodynamic inactivation using nanotized plant extracts of Andrographis paniculata in the form of a carbonaceous nanoparticle is established here through the fabrication of a Carbon Dot (CD). Study designLeaves extracts of Plant growth promoting bacteria (PGPR) elicited plants are transformed to CD to induce unique photophysical properties without any surface modification and passivation to achieve the enhanced antimicrobial activity. MethodsCD with diameter ∼ 20 nm synthesized through hydrothermal pyrolysis of elicited A. paniculata leaf extracts. The nanoscale dimensions and photophysical characteristics of the CD were confirmed by Transmission electron microscopy (TEM), powder X-ray diffraction (XRD), Ultraviolet-visible (UV–Vis), Fluorescence, and Fourier transform infrared spectroscopy (FTIR) characterizations. Antibacterial activity in both Gram-positive and Gram-negative bacteria was evaluated to determine the combined effect of the dark activity and visible light-induced photosensitization. ResultsSecondary metabolites are elicited by microbial inoculation to form nanotized phytoproducts in the present study, which does not rely on any polymeric or lipidic nanocarriers. In vitro, studies showed that the antibacterial effects of CDs against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under the irradiation of visible light depend on the bioactive components, their concentrations, and duration of light irradiation. The CD itself sustainably acts as a photo-antibiotic as well as produces reactive oxygen species (ROS). ConclusionThis study showed that PGPR elicited leaf extracts of A. paniculata-derived CDs used as antibiotic therapy, due to its effectiveness in eliminating synthetic drug-resistant microbes through reactive oxygen species (ROS) via photodynamic inactivation. In comparison to the unelicited phyto substrate, it served as a more effective option for “Natural-Antibiotic-Antibacterial Photodynamic Therapy” (APDT) applications.

N-Based Polydentate Ligands and Corresponding Zn(II) Complexes: A Structural and Spectroscopic Study

Herein, the structural and photophysical features of two N-based polydentate ligands and the corresponding Zn(II) complexes are investigated. The obtained compounds were characterized using different spectroscopic techniques and their optical properties are discussed in relation to their chemical structure, defined by single-crystal X-ray diffraction and mass spectrometry. The spontaneous and quantitative complexation, investigated by UV-Vis, fluorescence, NMR, IR spectroscopies and mass spectrometry, makes these N-based polydentate ligands interesting candidates for possible applications in chelation therapy and in Zn(II) sensors.

Enhanced photodynamic activity of asymmetric non-ionic Zn(II) phthalocyanine amphiphiles: Effect of molecular design on In vitro activity

We herein introduce the rational design, synthesis, and photophysical characterizations of three asymmetric Zn(II)Pcs (Pc-Glu4, Pc-Mal4, and Pc-PEG4) bearing four neutral hydrophilic substituents, namely glucosyl, maltosyl, and PEG, on the macrocyclic dual rims. The photodynamic activity of the attained structures, as compared to their fully derivatized hydrophilic versions (hexadeca-glucosylated Pc-Glu16 and PEGylated Pc-PEG16 and AzaPc-PEG16), on several cell lines, e.g., HeLa, SK-MEL-28, MCF-7, was investigated. Results revealed that the newly designed macrocycles were characterized by higher photodynamic activity with EC50 values in (sub)micromolar ranges, which is about two orders of magnitude better than for symmetric hydrophilic counterparts. This has been attributed to their higher uptake by cells as well as their significant interaction with bovine serum albumin and biomembranes. A preserved photodynamic activity during the treatment without incubation on endothelial cell lines (HUVEC and EA.hy928) was detected for the asymmetrical gluco-macrocycles, indicating a good potential for vascular-targeted PDT.

Development of Photoswitchable Tethered Ligands that Target the μ-Opioid Receptor.

Converting known ligands into photoswitchable derivatives offers the opportunity to modulate compound structure with light and hence, biological activity. In doing so, these probes provide unique control when evaluating G-protein-coupled receptor (GPCR) mechanism and function. Further conversion of such compounds into covalent probes, known as photoswitchable tethered ligands (PTLs), offers additional advantages. These include localization of the PTLs to the receptor binding pocket. Covalent localization increases local ligand concentration, improves site selectivity and may improve the biological differences between the respective isomers. This work describes chemical, photophysical and biochemical characterizations of a variety of PTLs designed to target the μ-opioid receptor (μOR). These PTLs were modeled on fentanyl, with the lead disulfide-containing agonist found to covalently interact with a cysteine-enriched mutant of this medically-relevant receptor.

A facile tert-butyl nitrite-assisted preparation of deamino graphitic carbon nitride (DA-gCN) as a photocatalyst for the C-H arylation of heteroarenes using anilines as radical source.

In pristine graphitic carbon nitride (g-CN), amino groups often function as structural defects that trap photogenerated charges, resulting in low photocatalytic activity as well as reaction with nitrite, aldehyde, etc., ensuing in poor product yield. Without significantly altering the optical characteristics, the removal of amino groups is necessary to increase the photocatalytic activity and structural stability of pristine g-CN. The deamino graphitic carbon nitride (DA-gCN-5) was prepared by tert-butyl nitrite (TBN)-treatment, characterized and used as a photocatalyst for the radical C-H arylation of heteroarenes using anilines as radical source. Indeed, the photophysical characteristics of DA-gCN-5 and those of pristine g-CN are very comparable, except that DA-gCN-5 has a fewer residual amino groups, higher crystallinity, and compressed structure with a different morphology. Moreover, DA-gCN-5-catalyzed C-H arylation reaction offers greater product yield in a shorter reaction time compared to that of pristine g-CN in the coupling between heteroarenes and the in situ generated aryl diazonium salts from anilines under visible light irradiation. The amino groups in pristine g-CN absorbed the TBN that was added to convert aniline into the appropriate diazonium ions during the reaction. As a result, deamino graphitic carbon nitride produced by chemical treatment has better photophysical properties and catalytic activity than pristine g-CN. Additionally, this is the first method that uses diazotization reaction for the preparation of deamino graphitic carbon nitride, as far as we are aware.

E- or Z-Isomers Arising from the Geometries of Ligands in the Mercury Complex of 2-(Anthracen-9-ylmethylene)-N-phenylhydrazine Carbothioamide.

An anionic mercury(II) complex of 2-(anthracen-9-ylmethylene)-N-phenylhydrazine carbothioamide (HATU) and two isomers of a neutral mercury(II) complex of the anion of the same ligand (ATU) were reported. The anionic complex [Hg(HATU)2Cl2]·CH2Cl2 had a monodentate HATU ligand (a neutral form of the ligand) and chloride ligands. The two conformational isomers were of the neutral mercury(II) complex Hg(ATU)2·2DMF. The two isomers were from the E or Z geometry of the ligands across the conjugated C=N-N=C-N scaffold of the coordinated ligand. The two isomers of the complex were independently prepared and characterized. The spectroscopic properties of the isomers in solution were studied by 1H NMR as well as fluorescence spectroscopy. Facile conversion of the E-isomer to the Z-isomer in solution was observed. Density functional theory (DFT) calculations revealed that the Z-isomer of the complex was stable compared to the E-isomer by an energy of 14.35 kJ/mol; whereas, E isomer of the ligand was more stable than Z isomer by 8.37 KJ/mol. The activation barrier for the conversion of the E-isomer to the Z-isomer of the ligand was 167.37 kJ/mol. The role of the mercury ion in the conversion of the E-form to the Z-form was discussed. The mercury complex [Hg(HATU)2Cl2]·CH2Cl2 had the E-form of the ligand. Distinct photophysical features of these mercury complexes were presented.

Effect of sandwiched YbCl3 layer thickness on exciton dynamics of Yb3+ doped CsPbCl3 perovskite photodetectors

Yb3+ doped CsPbCl3 metal halide perovskite photodetectors (PDs) in the structure of CsPbCl3(50 nm)/YbCl3(x nm)/CsPbCl3(50 nm), in which x ranges from 10 to 40 nm corresponding to the molar ratio from 6.3% to 25.2%, are fabricated by thermal evaporation on Si/SiO2 substrate. Photoresponse from 350 to 980 nm have been achieved with the optimal responsivity (R) of 3959, 5425, 955 A W−1 for the case of 20 nm YbCl3 at the wavelength (λ) of 420, 680 and 980 nm, respectively. A series of photophysical and electrical characterization has been performed and it is found that the remarkably improved photoresponse originates from the combining effects of upconversion and defects passivation from Yb3+. Moreover, the optimal YbCl3 thickness of 20 nm can be ascribed to the balance between upconversion and concentration quenching of Yb3+. The influence of the YbCl3 doping on the CsPbCl3 electronic structure is investigated and downshifting and stabilization of valence band maximum (VBM) can be attributed to the p-type doping and counteracting effect of Yb3+ and Cl−, respectively.

Valkyrie Probes: A Novel Class of Enzyme-Activatable Photosensitizers based on Sulfur- and Seleno-Rosamines with Pyridinium Unit.

The rational design of activatable photosensitizers (aPSs) uncaged by specific disease biomarkers is currently booming due to their positive attributes to achieve targeted photodynamic therapy (PDT). In this context, we present here the synthesis and detailed photophysical characterization of a novel class of hetero-rosamine dyes bearing sulfur or selenium as bridging heavy atom and 4-pyridyl meso-substituent as optically tunable group. The main feature of such photoactive platforms is the spectacular change of their spectral properties depending on the caging/decaging status of their 4-pyridyl moiety (cationic pyridinium vs. neutral pyridine). The preparation of two alkaline phosphatase (ALP)-responsive probes (named Valkyrie probes) was achieved through formal N-quaternarization with 4-phosphoryloxybenzyl, the traditional recognition moiety for this important diagnostic enzyme. Bio-analytical validations including fluorescence/singlet oxygen phosphorescence enzyme assays and RP-HPLC-fluorescence/-MS analyses have enabled us to demonstrate the viability and effectiveness of this novel photosensitizer activation strategy. Since sulfur-containing Valkyrie probe also retains high fluorogenicity in the orange-red spectral range, this study highlights meso-pyridyl-substituted S-pyronin scaffolds as valuable candidates for the rapid construction of molecular phototheranostic platforms suitable for combined fluorescence diagnosis and PDT.