Photoinduced Electron Transfer Process Research Articles

Ultrasensitive and Selective Nitrogen-Doped Fluorescent Carbon Dots Probe for Quantification Analysis of Trace Cu2+ in the Aqueous Environment.

As a typical non-ferrous metal, copper is heavily used in the manufacturing and chemical industries. Copper pollution has been demonstrated to have a significant detrimental impact on the natural environment, as well as causing irreparable damage to the human body, such as elevated Cu2+ levels have been identified as a factor in the pathogenesis of AD (Alzheimer's disease). In this study, novel nanoscale carbon dots Blue-CDs (B-CDs) were obtained by the solvothermal approach in formamide solution utilizing citric acid as the carbon source and ethylenediamine as the nitrogen dopant. The particle size of B-CD was assessed to be 2.17nm, with a quantum yield (QY) of 10.28%. The B-CDs were found to be extinguished upon exposure to Cu2+, which exhibited a good fluorescence detection linear relationship within the concentration range of 0.25-10.0 µM Cu2+, showing a limit of detection (LOD) is 0.18 µM. B-CDs have been effectively used for the measurement of Cu2+ in actual aqueous systems. It is due to the chemical reactions that take place among the B-CDs and the Cu²⁺ that make the sensor highly sensitivities and highly selectivities. The results of the experiment demonstrate that the fluorescence quenching process is a consequence of Cu2+ binding to the amino groups of carbon dots, forming complexes via a non-radiative photoinduced electron transfer process. In conclusion, the described simple sensing techniques could be effectively utilized as monitoring tools for Cu2+ in environmental waters.

Visible-Light-Induced Imine Hydrogenation Catalyzed by Thioxanthone-TfOH Complex.

Amino compounds are important molecules, commonly found in nature and widely applied in industrial production. Recently, photocatalysis has been discovered as an efficient method to synthesize amino compounds by promoting imine hydrogenation. In this work, a strategy of imine hydrogenation catalyzed by 2e- consecutive photoinduced electron transfer (ConPET) process of thioxanthone-TfOH complex (9-HTXTF) was thoroughly investigated with its reaction conditions optimized, substrate scope examined, and reaction mechanism elucidated, which provides an efficient method for synthesizing amino compounds.

Conformation Regulation of Perylene Diimide Derivatives by Lanthanide Coordination for Turn-On Fluorescence Sensing of Sarin Simulants.

Fluorescent metal-organic frameworks (MOFs) are promising sensing materials that have received much attention in recent years, in which the organic ligand conformation changes usually lead to variations of their sensing behavior. Based on this, in the present work, perylene diimide (PDI) derivatives with excellent photochemical properties closely related to their conformation and molecule packing fashion were selected as organic linkers to detect sarin simulant diethyl chlorophosphate (DCP). By the coordination interactions with large lanthanide cations through terminal carboxylate groups from the PDI derivative, a series of one-dimensional coordination polymers, named [Ln(PDICl4-2COO)(μ2-O)0.5(DMF)1.5] (SNNU-112, Ln = Yb/Tb/Sm/Nd/Pr/Gd/Eu/Er/Ce, PDICl4-2COOH = N,N'-bis(4-benzoic acid)-1,2,6,7-tetrachlorohydrazone-3,4,9,10-tetracarboxylic acid diimide) were synthesized. Regulated by the coordination process, the ligand undergoes a certain degree of conformational turnover and thus leads to an electron distribution change compared to free PDICl4-2COOH. Notably, the contact with the DCP molecule triggered a further ligand conformational conversion of PDI ligands in SNNU-112 and thus caused a fluorescence turn-on phenomenon realizing a well-defined fluorescence detection performance for DCP on the basis of a photoinduced electron transfer process. Among nine lanthanide MOFs, Yb-MOF sensor exhibited the lowest detection limit (4.36 ppb), fast response, high selectivity, and good recyclability. Such molecular conformation regulation of PDI derivatives by metal coordination may provide a new way for the exploration of fluorescent sensors.

Dual Fluorometric and Colorimetric Chemosensor Based on Poly(Arylene Ether Nitrile)s Functionalized Zn(II)Porphyrins for Selective Detection of Cyanide

AbstractPoly(arylene ether nitrile)s (PAENs) appended with Zn(II)‐porphyrin in varied molar percentages (5% and 10%) are developed as dual colorimetric and fluorometric sensors for highly sensitive and selective cyanide (CN−) detection. The materials, DP‐5%PAEN@Zn and DP‐10%PAEN@Zn, exhibit significant Soret band shifts at 420 ± 2 nm, accompanied by the appearance of a new absorption band at 436 ± 2 nm, indicating strong CN− binding with high association constants of 1.3 × 10⁴ M−¹ and 2.3 × 10⁴ M−¹, respectively. A prominent color change from purple to green allowed for naked eye detection. Spectrofluorimetric studies revealed turn‐off fluorescence with Stern‐Volmer constants (Ksv) of 99.85 × 103 M−¹ for DP‐5%PAEN@Zn and 121.08 × 103 M−¹ for DP‐10%PAEN@Zn, achieving limit of detection (LOD) of 0.177 and 0.099 ppb, respectively. DP‐10%PAEN@Zn demonstrated excellent sensitivity and selectivity toward CN−, and also reusability, as it remained functional after ten TFA treatment cycles. The mechanistic investigation, supported by photophysical, electrochemical, and DFT analyses, revealed a photoinduced electron transfer process via static quenching. Material stability is confirmed through photodegradability, prolonged time, temperature, and humidity testing. Prototype test kits are developed for real‐time visual CN− detection in remote and environmental samples (tap, lake, sewage, and soil). Additionally, a smartphone‐based color recognition assay is implemented for qualitative and quantitative analysis.

Effect of Anion-Directed Structural Tuning of Triazole-Containing Ag(I) Coordination Polymers for "Turn-on" Sensing of the Disulfide (-S-S-) Amino Acid over the Monosulfide (-SH) Form: Experiments and DFT Corroboration.

Identification of disulfide-peptide-bond-containing glutathione (GSSG) over the monosulfide form (GSH) remains a very challenging task because of their identical chemical properties. Although GSH detection has been well documented, selective detection of GSSG has rarely been reported. Here, four cationic Ag-based coordination polymers (Ag CPs) were synthesized using newly synthesized monotriazole linker 3-amino-5-(4H-1,2,4-triazol-4-yl)pyridine to selectively screen GSSG over GSH. The judicious choice of the counteranion in the metal salt changes the architecture, which affects the detection limit at the parts per million level. The restriction of the photoinduced electron transfer process is the driving reason for the enhancement of the fluorescence, owing to the favorable energy band gap match of the Ag CPs with GSSG over GSH. The de novo strategy for incorporating polar heteroatoms (N) into the CP network plays a pivotal role in the host-guest noncovalent interactions with donor-acceptor transfer of electrons, which was supported by X-ray photoelectron spectroscopy and density functional theory studies. The Ag CPs are thermochemically robust, recyclable, and work efficiently in a very short time (within ∼14-18 s) in different pH ranges. Additionally, detection of GSSG in serum samples was carried out with appreciable detection limits and recovery percentages (94.40-117.89%).

RhB intercalated Zr(VI)-bipyridine architecture for efficient ratiometric fluorescent response toward Cr(VI) analyte and decontamination of Cr(VI) and reactive dye via photochemical REDOX

It is extremely‌ imperative to enhance the sensing accuracy of water-stable Zr-MOFs for Cr(VI), because the single emission signal in a sole Zr-MOF is rather vulnerable to external factors. Interpolation of guest luminous species into Zr-MOF crystals presents a feasible way to achieve dual-emission signals. In this contribution, a highly water-stable Zr-MOF (Zr-bcu-22bipy44dc) which emits bright-blue fluorescence was deployed as matrix to intercalate fluorochrome Rhodamine B (RhB), creating a novel dual-emission (at 410 and 580 nm) luminescent platform, RhB@Zr-MOF. Then, it was utilized as a fluorescence probe to accurately detect trace-level Cr(VI) ions, by assessing the relative fluorescence intensity (IR) difference between the host Zr-MOF (I410) and the guest RhB (I580). Interestingly, the septal interpolation of luminescent species within Zr-MOF matrix effectively suppresses aggregation-induced quenching (ACQ), which tends to occur easily for RhB molecules. Moreover, its determined detection limits (DL) for CrO42- (6.13 ppb) and Cr2O72- (10.04 ppb) ions have been remarkably enhanced by approximately 4.92-fold and 3.66-fold, respectively, compared to the initial Zr-MOF (30.11 and 36.76 ppb). DFT and TD-DFT calculations have confirmed that the orange-yellow photoluminescence exhibited by RhB@Zr-MOF should be attributed to the PET process inherent to the intercalated RhB molecules, rather than the commonly accepted intermolecular Förster resonance energy transfer (FRET) mechanism or the photo-induced electron transfer (PET) effect previously identified by us. Efficient antenna effect of RhB module synergizes with Zr-MOF's appropriate band structure, also enables RhB@Zr-MOF convincing ability to photochemically deoxidize Cr(VI) and bleach reactive dark blue K-R (K-R)

Antenna effect on Zn(II) porphyrin-based molecular ensembles for the detection of 2,4-dinitrophenol through energy and electron transfer process.

Twomodular systems were synthesizedcomposed of triphenylamine (ZnTPAP) and pyrene (ZnPyP) covalently linked at meso position of the Zn(II) porphyrins. Both compounds behaved as energy transfer antenna and orthogonal units to enhance the electron donating ability of Zn(II) porphyrins. Detailed photophysical and aggregation studies reveal that an appreciable electronic interaction exists between peripheral units to the porphyrin π-system so that they behave like strong donor materials. The electrochemical and computational studies demonstrate delocalization of the frontier highest occupied molecular orbital (-5.08eV) over the triphenylamine entities (ZnTPAP) in addition to the porphyrin macrocycle. Fluorescence experiments withZnTPAP and ZnPyP in the presence ofdifferent nitro analytes at various concentrations show turn-off fluorescence behaviour and exhibit superior selectivity towards 2,4-dinitrophenol (DNP) with limit of detection (LOD) of ~ 2.3 and 9.2ppm for ZnTPAP and ZnPyP. Photoinduced electron transfer process is involvedin the static and dynamicfluorescence quenching process. A Stern-Volmer quenching association constant (Ksv) determination revealed that ZnTPAP is more sensitive than the ZnPyP. This is attributed to thestrong donating behaviour of TPA unitscaused by intermolecular interaction through metal center and strong π-π interactions with nitro analytes. The present study provides new insights into the ability to tune the affinity and selectivity of porphyrin-based sensors utilising electronic factors associated with the central Zn(II) ion. Furthermore, a smartphone-interfaced portable fluorimetric method by recognising colour variations in RGB and the luminance (L) values facilitate sensitive and real-time sensing at low concentration levels will have a significant impact on development of a new class of chemosensors.

Exploring photophysical behavior and fullerene-induced quenching in difluoroboron flavanone [formula omitted]-diketonates for application in organic electronic devices: Experimental and theoretical analysis

The photophysical properties of two difluoroboron flavanone β-diketonates (DK1 and DK2) and their interaction with fullerene (C60) in toluene solution and spin-coated films were investigated using time-correlated single-photon counting, absorption spectroscopy, and steady-state fluorescence spectroscopy. In molecular crystal, the complexes exhibited red-shifted absorption and emission relative to their spectra in solution. Additionally, both complexes displayed bi-exponential decay behavior in time-resolved fluorescence measurements, indicating their capability to form both H and J types of aggregates in the solid state. The introduction of C60 resulted in significant fluorescence quenching and reduced excited-state lifetimes for both complexes. This quenching, observed in both solution and spin-coated films, was primarily driven by photo-induced electron transfer (PET) processes, underscoring the potential of these complexes as donors in fullerene-based heterojunction organic solar cells. To elucidate the process of aggregate formation and the impacts of different dimerization types within the crystalline structure of the complexes, first-principles calculations using Density Functional Theory (DFT) and time-dependent density functional theory (TD-DFT) were performed. We also employed DFT to explore various DK configurations on the fullerene surface, evaluating intermolecular distances and formation energies. These calculations highlighted the energetically favourable gap between the low-lying LUMO levels of the complexes and C60, confirming their suitability for such applications.

A theoretical comprehension of photophysical processes in Cu2+ sensing by 1,7-di(2-pyridyl)bispyrazolo[3,4-b:4′,3′-e]pyridines

Due to its simplicity and sensitivity, metal ion sensing by fluorescent probes has a high biological and ecological impact, and several preliminary applications for Cu2+ have been found. However, the poor understanding of photophysical phenomena by which probes work has led to the growth of unhelpful literature. In this way, 4-aryl-1,7-di(pyridin-2-yl)bispyrazolo[3,4-b:4′,3′-e]pyridines Py2BP2a-c were studied as tridentate ligands in developing the probe Py2BP2a (Ar = Ph, LODCu2+ = 26 nM); thus, this previous work is completed herein by DFT/TD-DFT studies to understand the sensing process. The basal and first excited state of Py2BP2a-c (Ar: Ph, 4-An, 4-Py) and the parent l,4,7-triphenylbispyrazolo[3,4-b:3′,4′-e]pyridine Ph3BP2 were optimised. Results suggest that the probes' fluorescence is due to a twisted intramolecular charge transfer (TICT) and ICT processes around the 4-aryl and 1,7-dipyridin-2-yl groups; likewise, the fluorescence turn-off in the presence of Cu2+ by probe Py2BP2b is due to a photoinduced electron transfer (PET) process, favouring a ligand-to-metal charge transfer (LMCT). These findings enhance our understanding of the sensing process and open new possibilities for its applications in various fields.

Strong Electrochemiluminescence Response Derived from Ionic Chiral Covalent Organic Frameworks for Enantioselective Discrimination of Amino Acid Enantiomers via an Electrostatic Attraction Effect.

Porous chiral materials accompanied by electrochemiluminescence (ECL) activity are rarely reported for enantioselective discrimination because of the big challenges to integrate the stereogenic center and ECL-active unit in the backbone. In the present study, ionic chiral covalent organic frameworks (iCCOFs) consisting of the pyridinium unit as the ECL-active species were prepared by a facile strategy. We were amazed that such iCCOFs could display strong cathodic ECL responses. Meanwhile, the as-prepared ECL-active iCCOFs performed enantioselective ECL quenching toward amino acid enantiomers, attributed to the enhanced photoinduced electron transfer process derived from the formed complex between the iCCOFs and amino acids via an electrostatic attraction effect. The iCCOF with an (S)-configuration was prone to interact with l-amino acids, producing a lower ECL intensity. The maximum intensity ratio between the d- and l-enantiomers was 33.0. Finally, the enantiomeric compositions of the measured amino acids presented a good linear relation with the obtained ECL intensity, which was fit for the determination of samples with unknown enantiomeric purity. In brief, the obtained results convince us that this study advances a new generation of ECL-active iCCOFs and displays great potential in enantioselective sensing.

Dual pH-responsive polypeptide nanoprobes for lysosomes enhanced bioimaging and tumor photothermal therapy under 1064 nm irradiation

Cancer cell precise fluorescence imaging and following tumor photothermal therapy have garnered ongoing interest. Lysosomes in cancer cells in a typical acidic environment can be used for smart bioimaging, and intelligent NIR-II fluorescence probes are attractive for tumor phototheranostics. Here, we successfully synthesized a pH-responsive NIR-II fluorescent dye FPZ and the introduction of N-methylpiperazine moiety at the ring position in the dye-endowed FPZ with fluorescence enhancement under acidic response. A pH-sensitive amphiphilic polypeptide was selected as the carrier to prepare FPZ-PN nanoparticles, which could be disassembled under acidic stimulation for efficient drug delivery and enrichment, and its fluorescence was significantly restored and enhanced (fluorescence enhancement of about 4.2 times) because of the blockage of the photoinduced electron transfer process, which allowed for efficient NIR-II fluorescence imaging, especially the lysosomes in cancer cells. In addition, the nanoparticles exhibited great photostability and a significant photothermal effect, with a photothermal conversion efficiency reaching as high as 69.96 % when subjected to a 1064 nm laser irradiation, which can effectively kill tumor cells. Thus, this work provides a new effective strategy for designing smart-responsive nanomedicine systems for precise localization and tumor elimination.

Selective monodeuteration enabled by bisphosphonium catalyzed ring opening processes

The selective incorporation of a deuterium atom into small molecules with high selectivity is highly valuable for medical and chemical research. Unfortunately, this remains challenging due to the complete deuteration caused by commonly used hydrogen isotope exchange strategies. We report the development of a photocatalytic selective monodeuteration protocol utilizing C–C bond as the unconventional functional handle. The synergistic combination of radical-mediated C–C bond scission and deuterium atom transfer processes enables the effective constructions of benzylic CDH moieties with high selectivity for monodeuteration. The combinational use of a bisphosphonium photocatalyst, thiol catalyst, and CH3OD deuteration agent provides operationally simple conditions for photocatalytic monodeuteration. Moreover, the photoinduced electron transfer process of the bisphosphonium photocatalyst is elucidated through a series of spectroscopy experiments, identifying a peculiar back electron transfer process that can be regulated by subsequent nucleophilic additions.

A multifunctional probe that responds sequentially to hydrogen sulfide and hypochlorous acid

Hydrogen sulfide is reductive and hypochlorous acid is oxidizing, both of which play an important role in maintaining the redox balance in vivo. Therefore, the development of a multifunctional probe that can simultaneously detect H2S and HClO has a crucial role. We have developed a novel sequence-specific probe (FS) that enables a multifunctional response to H2S and HClO in dual channels. Due to the presence of the PET (Photoinduced Electron Transfer) process, the fluorescence of FS was quenched. When FS responds to H2S, a new compound (FO) is formed, showing red fluorescence. FO further reacts with HClO to generate another compound (FO-O) with green fluorescence. FS can respond quickly to H2S and HClO with good selectivity. FS can be used to detect the dynamic changes of H2S and HClO in cells and has the ability to specifically target lipid droplets, which is of great significance for the prevention and diagnosis of related diseases.

Visible-Light Photoredox-Catalyzed Direct Carboxylation of Tertiary C(sp3)-H Bonds with CO2: Facile Synthesis of All-Carbon Quaternary Carboxylic Acids.

Direct carboxylation of C-H bonds with CO2 represents an attractive strategy to synthesize valuable carboxylic acids with high atom, step, and redox economy. Although great progress has been achieved in this field, catalytic carboxylation of tertiary C(sp3)-H bonds still remains challenging due to their inherent inertness and significant steric hindrance. Herein, we report a direct carboxylation of tertiary benzylic C(sp3)-H bonds with CO2 via visible-light photoredox catalysis. Various all-carbon quaternary carboxylic acids, which are of significant importance in medicinal chemistry, are successfully obtained with high yields. This direct carboxylation is characterized by good functional group tolerance, broad substrate scope, and mild operational conditions. Furthermore, our methodology enables the efficient and rapid synthesis of key drug or bioactive molecules, such as carbetapentane, caramiphen, and PRE-084 (σ1 receptor agonist), and facilitates various functionalizations of C(sp2)-H bonds using the directing ability of target carboxylic acids, thus highlighting its practical applications. Mechanistic studies indicate that a carbanion, which serves as the key intermediate to react with CO2, is catalytically generated via a single electron reduction of a benzylic radical through a consecutive photoinduced electron transfer process.

Excitation energy transfer based naphthalimide-boron-dipyrromethene dyads as two-photon fluorescent probes for palladium(0) detection and live cell imaging

Increasing industrial demand has accelerated the consumption and contamination of palladium (Pd) worldwide. The implementation of fluorescent probes, especially with two-photon excitation, holds great promise for Pd detection in environmental and biological analysis. In this work, two naphthalimide (NPI)-boron-dipyrromethene (BDP) dyads (named NBH and NBN) were developed as two-photon fluorescent probes for Pd(0) detection based on an excitation energy transfer (EET) strategy, employing NPI as the energy donor and BDP as the acceptor. Spectroscopic studies revealed that both probes exhibited a fast response to Pd(0) in a pronounced fluorescence "ON-OFF" manner. The Pd-catalyzed Tsuji-Trost reaction activated an intramolecular photoinduced electron transfer (PET) process between the aniline and BDP moieties, resulting in the fluorescence quenching of the BDP fluorophore. The reaction-based probes exhibited excellent sensitivity and selectivity for Pd(0) species with a detection limit as low as 2.4 nM. These probes were successfully applied to the determination of Pd residues in drug, soil, and water samples. A simple smartphone-based platform was also constructed to determine Pd(0) via an RGB reader. With negligible cytotoxicity, confocal imaging study validated their feasibility of monitoring Pd(0) in living cells through multiple excitation channels.

Facile synthesis and tunable fluorescent properties of a new D-π-A isocoumarin: Applications in encryption and OLED technology

A facile synthesis of a new D-π-A isocoumarin (ICP-NH2) with only two steps under mild conditions through O-acylation/Wittig/reduction reaction has been established. The readily accessible phosphonium salt precursor 1 and 4-nitrobenzoyl chloride 2 produced intermediate ICP-NO2 in the presence of triethylamine. Subsequently, ICP-NO2 underwent conversion to ICP-NH2 through the reduction of stannous dichloride. ICP-NH2 exhibits enhanced fluorescence overcoming the photo-induced electron transfer (PET) process in ICP-NO2. ICP-NH2 demonstrates a significant change in fluorescence from blue to green in various polar solvents, and DFT analysis confirmed that its solvatochromism is attributed to intramolecular charge transfer (ICT) effect. ICP-NH2 undergoes noticeable acidochromism based on reversible protonation and deprotonation reactions with TFA and TEA, leading to periodic changes in fluorescence from green to dark blue. This phenomenon can be utilized in designing reusable encryption technology. Additionally, ICP-NH2 can be employed in the fabrication of a cyan green OLED device.

Exploring the reaction mechanistic pathway for the sensing of G-Series nerve agent with Kemp's triacid derivative: A computational study

Kemp's triacid derivative have been reported as a candidate for sensing of nerve agents employing the photoinduced electron transfer (PET) processes. The sensor probe molecules were prepared with primary alcohol in very close proximity to a tertiary amine to acylate the alcohol with rapid intramolecular N-alkylation to produce quaternary ammonium salt. The reaction pathways for the formation of quaternary ammonium salt and isomethyl propyl phosphonate remain unexplored. In this report, the mechanistic pathways of G-series nerve agents sarin and its simulant diethylcholorophosphate (DCP) with Kemp's triacid derivatives has been explored computationally. The calculations performed with B3LYP-D3/6-311+G(d,p) level of theory in DCM solvent revealed that the reaction proceeds via intermolecular and intramolecular SN2 pathways. The probe molecule is sterically hindered, therefore, the frontside and backside SN2 reaction pathways have been examined. The computed results suggest that the first intermolecular SN2 reaction of Kemp's triacid derivatives (I &II) with sarin for the backside attack is energetically favored compared to the frontside attack and the following intramolecular SN2 reaction is a barrierless process. The calculations performed with simulant diethylcholorophosphate (DCP) and Kemp's triacid derivatives (I &II) show that the reactions are energetically more facile compared to the nerve agent sarin molecule. The Distortion-Interaction model and ΔNBOSteric analysis showed that the back side is energetically favored over the front side attack in such SN2 reactions. The designed Kemp's triacid derivative (II) with phosphorus center for sensing sarin and (DCP) suggests that the size of the hetero centers are important to facilitate the reaction in the probe molecule.

Near-Infrared Fluorescent Turn-On Probe for Selective Detection of Hypochlorite in Aqueous Medium and Live Cell Imaging.

Hypochlorite, as an important reactive oxygen species (ROS), plays a vital role in many physiological and pathological processes, but an excess concentration of hypochlorite (ClO-) may become toxic to humans and cause disease. Hence, the selective and rapid detection of hypochlorite (ClO-) is necessary for human safety. Here, we report a novel near-infrared (NIR) fluorescence "turn-on" and highly selective benzophenoxazinium chloride-based fluorescent probe, BPH (benzophenoxazinium dihydroxy benzaldehyde), for hypochlorite detection. Due to hypochlorite-induced vicinal diol oxidation to the corresponding ortho benzoquinone derivative, the photoinduced electron transfer (PET) process, which was operating from vicinal diol to the benzophenoxazinium chloride receptor moiety, was suddenly inhibited, as a result of which strong NIR fluorescence "turn-on" emission was observed. The detection limit of BPH was found to be 2.39 × 10-10 M, or 0.23 nM. BPH was successfully applied for exogenous and endogenous hypochlorite detection in live MDA-MB 231 cells.

On-site monitoring of L-adrenaline neurotransmitter in biological samples by chitosan oligosaccharide derived carbon dots

Carbon quantum dots (CDs) are fascinating fluorescent nanomaterial for spectrofluorimetry sensor applications, owing to the fact of its strong chemical stability, high quantum yield and high photostability. At this instance, we have developed the fluorescent sensing technique to detect the L-adrenaline (L-Adr) by nitrogen-doped carbon quantum dots as a sensing probe. The nitrogen-doped carbon dots was synthesized using chitosan oligosaccharide by hydrothermal method. The synthesized chitosan oligosaccharide derived CDs (COL-CDs) exhibits blue fluorescence under UV light and the size of the carbon quantum dots is 3.39 ± 0.08 nm calculated from HR-TEM image. The hormone called L-Adr found in the human body is crucial for controlling visceral processes. Utilizing the process of photo-induced electron transfer (PET), the previously mentioned COL-CDs have applied to sense the L-Adr. The sensing mechanism have explained clearly using Rehm-Weller equation by calculating ΔG. Tap water, blood serum, urine and adrenaline drug samples employed as real sample for the sensing L-Adr. A reagent free paper-based kit established for the purpose of on-site monitoring L-Adr. The smartphone’s colour picker software used to measure the RGB intensity from the paper-based kit.

Photoelectron-transfer-effect grafting: Validation of a generalized strategy for fluorescence and photoelectrochemical dual-mode detection of hydrogen sulfide

BackgroundThe progress of modern research is constantly fueled by the convergence of multiple technologies. Despite the enormous potential of both fluorescence (FL) and photoelectrochemical (PEC) technologies, the development of synergistic PEC-FL sensing platforms that combine the advantages of both is still in its early stages due to their relatively recent inception. Hydrogen sulfide (H2S), possessing dual irritant and asphyxiating traits, poses challenges for environmental preservation and human health. The development of the PEC-FL detection methodology for H2S in complex environmental settings is imperative. ResultsCombining FL and PEC sensing techniques, this work presented a new concept of photoinduced electron-transfer (PET) effect grafting for dual-mode fluorescence and PEC analysis. Briefly, a well-designed fluorescent molecule (BTFM-DNP) featuring the PET effect was synthesized and implemented to modulate the photoelectric response of the indium tin oxide (ITO)/BiOI photocathode electrode. After reacting with H2S, the thiolysis of dinitrophenyl ether eliminated the intramolecular PET effect and recovered the significant fluorescence of the probe. Remarkably, the newly formed 2,4-dinitrobenzenethiol (DBT) with strong electron-withdrawing groups was then grafted to the ITO/BiOI photoelectrode and achieved the successful transfer of the PET process, resulting in a sharp decrease in photocurrent. The as-developed dual-mode protocol exhibited good performance in terms of ultra-sensitivity, high selectivity, fast response, and a wide detection range from 1 pM to 80 μM. SignificanceThe newly developed PEC-FL sensing platform can be applied to detect H2S levels in both the environment and food. This study demonstrates a promising synergy between fluorescent probes and PEC sensors, offering a novel perspective on the advancement of multi-mode analysis techniques. This approach has the potential to significantly enhance detection accuracy and reliability.