Sulfur Species Research Articles

Enhancement of Li/S Battery Performance by a Modified Reduced Graphene Oxide Carbon Host Decorated with MoO3.

Electrochemical energy storage systems based on sulfur and lithium can theoretically delivery high energy with the further benefit of low cost. However, the working mechanism of this device involves the dissolutions of sulfur to high-molecular weight lithium polysulfide (LiPs with general formula Li2Sn, n>4) in the electrolyte during the discharge process. Therefore, the resulting migration of partially dissociated LiPs, by diffusion or under the effect of the electric field, to the lithium anode activates an internal shuttle mechanism, reduces the active material and in general leads to loss of performance and a reduced cycling stability. These drawbacks poses challenges to the commercialization of Li/S cells in the short term. In this study, we report on the decoration of reduced graphene oxide with MoO3 particles to enhance interactions with LiPs and retain sulfur at the cathode side. The combination of experiments and density functional theory calculation demonstrated improvements in binding interactions between the cathode and sulfur species, enhancing the cycling stability of the Li/S half-cell.

Metagenome mining and functional analysis reveal oxidized guanine DNA repair at the Lost City Hydrothermal Field.

The GO DNA repair system protects against GC → TA mutations by finding and removing oxidized guanine. The system is mechanistically well understood but its origins are unknown. We searched metagenomes and abundantly found the genes encoding GO DNA repair at the Lost City Hydrothermal Field (LCHF). We recombinantly expressed the final enzyme in the system to show MutY homologs function to suppress mutations. Microbes at the LCHF thrive without sunlight, fueled by the products of geochemical transformations of seafloor rocks, under conditions believed to resemble a young Earth. High levels of the reductant H2 and low levels of O2 in this environment raise the question, why are resident microbes equipped to repair damage caused by oxidative stress? MutY genes could be assigned to metagenome-assembled genomes (MAGs), and thereby associate GO DNA repair with metabolic pathways that generate reactive oxygen, nitrogen and sulfur species. Our results indicate that cell-based life was under evolutionary pressure to cope with oxidized guanine well before O2 levels rose following the great oxidation event.

The role of hydrothermal processes and the formation of the J-M reef and associated rocks of olivine-bearing zone I of the Stillwater Complex, Montana

AbstractSeveral lines of evidence, including hydrous melt inclusions and unusually Cl-rich apatite, have been used to suggest that the reappearance of olivine and PGE-sulfide of the J-M Reef in the Stillwater Complex, Montana, is due to fluid infiltration and hydration melting. This study builds upon the hydration melting model using the programs MELTS and PELE with Stillwater bulk rock compositions for the original protolith. Cl-bearing phases are not modeled by MELTS and thus simple oxide mixtures of either a pure H2O or a H2O + Na2O “faux brine” are added to norite, gabbronorite, and melanorite protoliths at 1050 °C at 2 kbar pressure, conditions for which the nominally “dry” protolith is > 95% solid. Incongruent hydration melting results in up to 37% olivine produced in the melanorite. The olivine Fo content is a function of the partial melt retained on cooling, and ranges between 76 and 86, overlapping the natural range of olivine compositions observed in the rocks. Modeling with the PELE program, which includes a silicate liquid Cl component, sulfur species, and a more complex C-O–H-S fluid, suggests that, for CO2-rich fluids, fluid metal concentrations on the order of 25 ppm Pt, 75 ppm Pd, 0.03 wt.% Cu, and 0.20 wt.% Ni at a fluid/rock mass ratio of ~ 0.25 are needed to account for the observed ore grades. Sulfide and ore metals are readily remobilized for more H2O-rich fluids, consistent with heterogeneous distribution of sulfide and regionally variable ore grades.

Nano‐LaMnO3 Modified Separator for Enhanced Redox Reaction Kinetics and Electrochemical Performance of Lithium‐Sulfur Batteries

AbstractThe “shuttle effect” and sluggish conversion reaction kinetics of polysulfides seriously hinder the practical application of Li−S batteries. In this study, nano‐sized LaMnO3 (N‐LMO) with typical perovskite structure combined with highly‐conductive carbon black (SP) was introduced on the commercial separator to fabricate a functional surface modification. It is found that the polar N‐LMO with abundant active sites offers strong chemisorption towards the soluble polysulfides meanwhile accelerates their redox conversion, and the conductive SP contributes to extra spots to reactivate the trapped sulfur species. Consequently, the synergistic effect of adsorption‐catalysis‐conduction built by the cooperative N‐LMO/SP modification greatly enhances the sulfur redox kinetics as well as suppresses the polysulfide shuttling not at the expense of weakening Li‐ion transport, which endows the Li−S cell with a high initial discharge capacity of 1143.6 mAh g−1 at 0.2 C and a capacity decay rate of only 0.072 % per cycle at 1 C over 500 cycles.

A ratiometric fluorescent probe with dual-targeting capability for heat shock imaging

HSO3− is an important reactive sulfur species that maintains the normal physiological activities of living organisms and participates in a variety of redox homeostatic processes. It has been found that changes in HSO3− levels is closely related to the heat stroke phenomenon of the organism. Heat stroke causes damage to normal cells, which in turn causes damage to the body and even death. It is crucial to accurately monitor and track the physiological behavior of HSO3− during heat stroke. Herein, a ratiometric multifunctional fluorescent probe DRM-SO2 with dual-targeting ability to rapidly and precisely recognize HSO3− being constructed based on the FRET mechanism. DRM-SO2 has extra Large Stokes shift (216 nm), very high sensitivity (DL = 12.2 nM), fast response time and good specificity. When DRM-SO2 undergoes Michael addition with HSO3−, the fluorescence emission peak was blue-shifted from 616 nm to 472 nm, and a clear ratiometric signal appeared. The interaction between lysosomes and mitochondria in maintaining cellular homeostasis was investigated by the dual-targeting ability of the probe using HSO3− as a mediator. DRM-SO2 achieved successful targeting and real-time monitoring of exogenous and endogenous HSO3− in the cells. More importantly, imaging experiments in heat stroke mice revealed high HSO3− expression in intestinal tissues. This provides new ideas and research tools for early prevention of heat stroke-induced diseases such as intestinal injuries. In addition, the semi-quantitative monitoring experiments for paper-based visualization of HSO3− make the probe promising for the design of portable detectors.

An Expanded Palette of Fluorescent COS/H2S‐Releasing Donors for H2S Delivery, Detection, and In Vivo Application

AbstractHydrogen sulfide (H2S) is an important reactive sulfur species that is involved in many biological functions, and H2S imbalances have been indicated as a potential biomarker for various diseases. Different H2S donors have been developed to deliver H2S directly to biological systems, but few reports include donors with optical responses that allow for tracking of H2S release. Moreover, donor systems that use the same chemistry to deliver H2S across a palette of fluorescent responses remain lacking. Here we report five thiol‐activated fluorescence turn‐on COS/H2S donors that utilize blue, yellow, orange, red, and near infrared‐emitting dyes functionalized with an H2S‐releasing sulfenyl thiocarbonate scaffold. Upon treatment with thiols, each donor provides a fluorescence turn‐on response (3–310‐fold) and high H2S release efficiencies (>60 %). Using combined electrode and fluorescence experiments, we directly correlate the measured H2S release with the fluorescence response. All donors are biocompatible and release H2S in live cell environments. In addition, we demonstrate that the NIR donor allows for imaging H2S release in live rats via subcutaneous injection of the donor loaded into an alginate gel, which to the best of our knowledge is the first in vivo tracking of H2S release from a fluorogenic donor in non‐transparent organisms.

A Volcano Correlation between Catalytic Activity for Sulfur Reduction Reaction and Fe Atom Count in Metal Center.

Sulfur reduction reaction (SRR) facilitates up to 16 electrons, which endows lithium-sulfur (Li-S) batteries with a high energy density that is twice that of typical Li-ion batteries. However, its sluggish reaction kinetics render batteries with only a low capacity and cycling life, thus remaining the main challenge to practical Li-S batteries, which require efficient electrocatalysts of balanced atom utilization and site-specific requirements toward highly efficient SRR, calling for an in-depth understanding of the atomic structural sensitivity for the catalytic active sites. Herein, we manipulated the number of Fe atoms in iron assemblies, ranging from single Fe atom to diatomic and triatomic Fe atom groupings, all embedded within a carbon matrix. This led to the revelation of a "volcano peak" correlation between SRR catalytic activity and the count of Fe atoms at the active sites. Utilizing operando X-ray absorption and X-ray diffraction spectroscopies, we observed that polysulfide adsorption-desorption and electrochemical conversion kinetics varied up and down with the incremental addition of even a single iron atom to the catalyst's metal center. Our results demonstrate that the metal center with exactly two iron atoms represents the optimal configuration, maximizing atom utility and adeptly handling the conversion of varied intermediate sulfur species, rendering the Li-S battery with a high areal capacity of 23.8 mAh cm-2 at a high sulfur loading of 21.8 mg cm-2. Our results illuminate the pivotal balance between atom utilization and site-specific requirements for optimal electrocatalytic performance in SRR and diverse electrocatalytic reactions.

Characterization of polysulfides (Sx2−) in seawater euxinic conditions by electroanalytical methods

Polysulfides (Sx2−) are important reduced sulfur species (RSS) that play a role in numerous environmental processes. A sound analytical method for the measurement of Sx2− in euxinic waters is lacking. In this work, differential pulse voltammetry (DPV) at the Hg electrode was used to measure the presence of Sx2− in a model seawater solution and an euxinic marine lake (Rogoznica Lake - RL Croatia), in which the concentration of RSS, mainly HS−, varies between 100 and 4000 μM. In the DPV, an adsorption phenomenon associated with Sx2− reduction on Hg produces a characteristic current minimum at −1.0 V (vs. Ag/AgCl), the magnitude of which is proportional to the concentration of polysulfidic sulfur.The DPV current minima were recorded in the model solution K2Sx NaCl/NaHCO3 (pH ~ 8.2) in a concentration range from 10 to 100 μM of polysulfidic sulfur. Total RSS was measured by cyclic voltammetry, and sampled DC voltammetry showed the ratio between HS− and S0 within the Sx2−. Using the same methodology, the presence of Sx2− below the chemocline enriched by photoptrophic sulfur bacteria was measured in the euxinic layer of RL at concentrations of up to 70 μM of polysulfidic sulfur. The results suggest that euxinic RL samples can be considered as polydisperse solutions of S0 or of S-rich compounds that can change their physicochemical properties and speciation during sample manipulation. These changes can be detected by electrochemistry. Atomic force microscopy proved the release of bacterial cellular S0 during the acidification and purging step in the electrochemical measurements, which contributed to the voltammetric RSS signal.

An AND-Gate Photoacoustic Probe for Cys and H2S Precise Photoacoustic Sensing in Localized Tumors.

Photoacoustic (PA) tomography has shown many promising aspects in noninvasive and precise imaging of deep-localized biomarkers. However, these traditional single-locked PA probes always face challenges in precise PA imaging with high specificity. Here, we report a novel AND-gate photoacoustic probe, BAE, to improve tumor imaging accuracy via the combination of two tumor-associated biomarkers, cysteine (Cys) and hydrogen sulfide (H2S). Only when Cys and H2S are concurrently introduced into the detection system does the absorption of BAE red-shift from the initial 680 to 810 nm, thereby showing a 5.29-fold enhancement in its PA signal at 810 nm. The good specificity of BAE is proven, since an obvious PA signal could be observed only in the solution containing both Cys and H2S and was not affected by other reactive sulfur species. After being taken up by tumors with the assistance of a nanomicelle, the AND-gate PA probe BAE was applied for dynamic real-time monitoring of Cys and H2S in vivo, achieving precise identification of tumors. This AND-gate PA probe provides a potential technical tool for precise sensing analysis of deep-seated diseases.

Mechanism of the desulfurization route of the reduction of SO2 on carbons. Dimerization of Disulfur and Tetrasulfur

AbstractThe desulfurization of carbons modified with SO2 was studied as a dispersion in boiling cyclohexane (81°C) using activated carbon (mAC) and graphene oxide (mGO), modified by SO2. The steady‐state species in the carbon matrix after the catalytic reduction of SO2 was considered a trisulfane. For mAC, there was a burst of a sulfur species identified as S2 by UV spectrum with a maximum at 217 nm (εM at 217 nm = 2.56 × 103) that showed a second‐order decay of absorbance with = 47.29 M‐1·sec‐1 (= 18.1 kcal·mol‐1). The product was postulated to be S4. No other consecutive reaction was observed because of the possible adsorption of S4 in the carbon matrix. The desulfurization of mGO was shown by XPS and the kinetics were a second‐order decay up to 16 min ( 18.41 M‐1·sec‐1;= 18.8 kcal·mol‐1) followed by a second‐order increase of absorbance with = 3.84 M‐1·sec‐1 (= 19.9), where the product showed a double maximum at 260‐285 nm typical of S8. These results are consistent with a mechanism of consecutive thermodynamically favorable dimerizations of S2 and S4 and with the desulfurization mechanism that has been previously postulated.

Novel Cu(II)-based metal–organic framework STAM-1 as a sulfur host for Li–S batteries

Due to the increasing demand for energy storage devices, the development of high-energy density batteries is very necessary. Lithium–sulfur (Li–S) batteries have gained wide interest due to their particularly high-energy density. However, even this type of battery still needs to be improved. Novel Cu(II)-based metal–organic framework STAM-1 was synthesized and applied as a composite cathode material as a sulfur host in the lithium–sulfur battery with the aim of regulating the redox kinetics of sulfur cathodes. Prepared STAM-1 was characterized by infrared spectroscopy at ambient temperature and after in-situ heating, elemental analysis, X-ray photoelectron spectroscopy and textural properties by nitrogen and carbon dioxide adsorption at − 196 and 0 °C, respectively. Results of the SEM showed that crystals of STAM-1 created a flake-like structure, the surface was uniform and porous enough for electrolyte and sulfur infiltration. Subsequently, STAM-1 was used as a sulfur carrier in the cathode construction of a Li–S battery. The charge/discharge measurements of the novel S/STAM-1/Super P/PVDF cathode demonstrated the initial discharge capacity of 452 mAh g−1 at 0.5 C and after 100 cycles of 430 mAh g−1, with Coulombic efficiency of 97% during the whole cycling procedure at 0.5 C. It was confirmed that novel Cu-based STAM-1 flakes could accelerate the conversion of sulfur species in the cathode material.

In situ self-activation strategy for the synthesis of double-layered S/Cl co-doped sorbents for elemental mercury removal from oxy-fuel combustion flue gas

Mercury capture from oxy-fuel combustion flue gas remains an enormous challenge for carbon capture and storage because of the lack of cost-effective, sulfur-resistant and water-resistant sorbent. In this work, double-layered S/Cl co-doped sorbents (CDSs) were synthesized through an in situ self-activation method i.e. co-pyrolysis of waste tire and PVC plastic, which were adopted for elemental mercury (Hg0) immobilization from oxy-fuel combustion flue gas. A synergistic effect between waste tire and PVC plastic was observed during co-pyrolysis. For this reason, chlorine was successfully doped into the CDSs in the form of covalent chlorine and ionic chlorine. The CDSs showed high Hg0 removal efficiency (>80 %) over a wide temperature range (20–140 °C) and excellent sulfur and water resistance. Both the initial Hg0 adsorption rate and adsorption capacity of CDSs were far higher compared with raw tire char. The Hg0 removal mechanisms were further proposed, where Hg0 preferentially reacted with covalent chlorine instead of active sulfur species. Density functional theory calculations revealed that the Hg0 adsorption over CDSs was chemisorption with an adsorption energy of −249.85 kJ/mol. The synergistic effect between sulfur and chlorine was beneficial for the formation of HgCl2 whereas it had negligible effect on the formation of HgCl.

One-pot Synthesis of High-capacity Sulfur Cathodes via In-situ Polymerization of a Porous Imine-based Polymer.

Lithium-ion batteries, essential for electronics and electric vehicles, predominantly use cathodes made from critical materials like cobalt. Sulfur-based cathodes, offering a high theoretical capacity of 1675mAhg-1 and environmental advantages due to sulfur's abundance and lower toxicity, present a more sustainable alternative. However, state-of-the-art sulfur-based electrodes do not reach the theoretical capacities, mainly because conventional electrode production relies on mixing of components into weakly coordinated slurries. Consequently, sulfur's mobility leads to battery degradation - an effect known as the "sulfur-shuttle". This study introduces a solution by developing a microporous, covalently-bonded, imine-based polymer network grown in-situ around sulfur particles on the current collector. The polymer network (i) enables selective transport of electrolyte and Li-ions through pores of defined size, and (ii) acts as a robust host to retain the active component of the electrode (sulfur species). The resulting cathode has superior rate performance from 0.1C (1360mAhg-1) to 3C (807mAhg-1). Demonstrating a high-performance, sustainable sulfur cathode produced via a simple one-pot process, our research underlines the potential of microporous polymers in addressing sulfur diffusion issues, paving the way for sulfur electrodes as viable alternatives to traditional metal-based cathodes.

One‐pot Synthesis of High‐capacity Sulfur Cathodes via In‐situ Polymerization of a Porous Imine‐based Polymer

Lithium‐ion batteries, essential for electronics and electric vehicles, predominantly use cathodes made from critical materials like cobalt. Sulfur‐based cathodes, offering a high theoretical capacity of 1675 mAh g–1 and environmental advantages due to sulfur's abundance and lower toxicity, present a more sustainable alternative. However, state‐of‐the‐art sulfur‐based electrodes do not reach the theoretical capacities, mainly because conventional electrode production relies on mixing of components into weakly coordinated slurries. Consequently, sulfur's mobility leads to battery degradation – an effect known as the “sulfur‐shuttle”. This study introduces a solution by developing a microporous, covalently‐bonded, imine‐based polymer network grown in‐situ around sulfur particles on the current collector. The polymer network (i) enables selective transport of electrolyte and Li‐ions through pores of defined size, and (ii) acts as a robust host to retain the active component of the electrode (sulfur species). The resulting cathode has superior rate performance from 0.1 C (1360 mAh g–1) to 3 C (807 mAh g–1). Demonstrating a high‐performance, sustainable sulfur cathode produced via a simple one‐pot process, our research underlines the potential of microporous polymers in addressing sulfur diffusion issues, paving the way for sulfur electrodes as viable alternatives to traditional metal‐based cathodes.

Chlorine bridge bond-enabled binuclear copper complex for electrocatalyzing lithium–sulfur reactions

Engineering atom-scale sites are crucial to the mitigation of polysulfide shuttle, promotion of sulfur redox, and regulation of lithium deposition in lithium–sulfur batteries. Herein, a homonuclear copper dual-atom catalyst with a proximal distance of 3.5 Å is developed for lithium–sulfur batteries, wherein two adjacent copper atoms are linked by a pair of symmetrical chlorine bridge bonds. Benefiting from the proximal copper atoms and their unique coordination, the copper dual-atom catalyst with the increased active interface concentration synchronously guide the evolutions of sulfur and lithium species. Such a delicate design breaks through the activity limitation of mononuclear metal center and represents a catalyst concept for lithium–sulfur battery realm. Therefore, a remarkable areal capacity of 7.8 mA h cm−2 is achieved under the scenario of sulfur content of 60 wt.%, mass loading of 7.7 mg cm−2 and electrolyte dosage of 4.8 μL mg−1.

MoC‐MoSe2 Heterostructures as Multifunctional Catalyst Toward Promoting the Stepwise Polysulfide Conversion for Lithium‐Sulfur Batteries

AbstractCatalyzing polysulfides conversion for lithium‐sulfur batteries is an efficient strategy to overcome the sluggish kinetics of polysulfides conversion as well as its serious shuttling effect. Due to the multistep and complicated phase transformation of sulfur species, the monofunctional catalyst can hardly promote the overall polysulfides redox process. Herein, a molybdenum‐based heterostructure is proposed, that facilitates the entire reduction process by tandemly catalyzing liquid‐liquid conversion and liquid‐solid conversion. It is uncovered that the MoC physiochemically immobilizes the soluble long‐chain polysulfide and accelerates the conversion between S8 to Li2S4 through adsorbing Li2S8 and extending its S─S bond distance. Then, the kinetics of Li2S precipitation is enhanced by facilitating the migration of Li2S4 from MoC to MoSe2. This is driven by the internal electric field at the heterogeneous interface and the low diffusion energy barrier on MoSe2 for Li2S4. Moreover, MoC‐MoSe2 exhibits the smallest degree of Li2S2 disproportionation throughout the reduction process. Consequently, the cell with MoC‐MoSe2/C/S cathode delivers an initial discharge‐specific capacity of 841.1 mAh g−1 and long‐term cycling stability with a capacity attenuation rate of 0.08% per cycle at 1.0 C. This work presents a novelty view to design a rational multifunction catalyst for sequentially accelerating the stepwise conversion of polysulfides.

Regulating charge transfer for enhanced PAA activation over sulfur-doped magnetic CoFe2O4: A novel strategy for simultaneous micropollutants degradation and bacteria inactivation

Micropollutants and bacteria are prevalent pollutants in wastewater, posing significant risks to ecosystems and human health. As peracetic acid (PAA) is being increasingly used as a disinfectant, activation of PAA by low-cost and high-performance activators is a promising strategy for wastewater treatment. In this study, the sulfur-doped magnetic CoFe2O4 (SCFO) is successfully developed for efficient PAA activation to simultaneously decontaminate and disinfect wastewater. PAA/SCFO-0.3 exhibits exceptional performance, degrading 100 % of 8 μM sulfamethoxazole (SMX) with a first-pseudo reaction rate of 1.275 min−1, and achieving 5.3-log inactivation of Escherichia coli (E. coli) within 3 min at a PAA dosage of 0.2 mM and catalyst dosage of 0.025 g/L (initial pH 6.5). Scavenging experiments and electron paramagnetic resonance (EPR) analysis identify CH3C(O)O• and CH3C(O)OO• as the dominant reactive species for SMX degradation. The sulfur species in SCFO-0.3 facilitate Co2+ regeneration and regulate charge transfer, promoting PAA activation for SMX degradation. Moreover, the PAA/SCFO-0.3 system demonstrates operational feasibility over a broad range of water matrices and has excellent stability and reusability (maintaining 93 % removal of SMX after 5 cycles), demonstrating its potential for industrial applications. This study provides insights into enhancing PAA activation through sulfur doping in transition metal catalysts and highlights the practical applicability of the PAA/SCFO-0.3 system as an advanced alternative to conventional disinfection for simultaneous decontamination and disinfection in wastewater.

Characterization of low molecular weight sulfur species in seaweed from the Antarctic continent.

Antarctic seaweeds are vital components of polar marine ecosystems, playing a crucial role in nutrient cycling and supporting diverse life forms. The sulfur content in these organisms is particularly interesting due to its implication in biogeochemical processes and potential impacts on local and global environmental systems. In this study, we present a comprehensive characterization of seaweed collected in the Antarctic in terms of their total sulfur content and its distribution among different classes of species, including thiols, using various methods and high-sensitivity techniques. The data presented in this paper are unprecedented in the scientific literature. These methods allowed for the determination of total sulfur content and the distribution of sulfur compounds in different fractions, such as water-soluble and proteins, as well as the speciation of sulfur compounds in these fractions, providing valuable insights into the chemical composition of these unique marine organisms. Our results revealed that the total sulfur concentration in Antarctic seaweeds varied widely across different species, ranging from 5.5 to 56gkg-1 dry weight. Furthermore, our investigation into the sulfur speciation revealed the presence of various sulfur compounds, including sulfate, and some thiols, which were quantified in all ten seaweed species evaluated. The concentration of these individual sulfur species also displayed considerable variability among the studied seaweeds. This study provides the first in-depth examination of total sulfur content and sulfur speciation in brown and red Antarctic seaweeds.

Effect of SO2 on the soot oxidation activity of flame spray pyrolysis-made manganese oxide catalyst in gasoline model exhaust

AbstractThis study deals with the effect of SO2 on the soot oxidation activity of flame spray pyrolysis-prepared manganese oxide in gasoline model exhaust. The catalyst was exposed to 15 and 30 ppm SO2 at 250 °C and was characterized by N2 physisorption, SO2-TPD, O2-TPD, DRIFTS, XPS and PXRD. It was shown that the SO2 adsorption results in the formation of surface sulfate, while the uptake increased from 26 to 45 μmol/g with growing sulfur content of the model exhaust. The sulfur adsorption reduces the mobility and availability of oxygen on the catalyst thus inhibiting the oxygen transport from gas phase over the catalyst to the contact points of the soot. Consequently, the soot oxidation activity, investigated with tight contact blends of catalyst and soot, decreases with inclining amount of sulfate. Finally, the sulfate species were mostly removed by thermal treatment at 705 °C, which additionally provoked catalyst sintering. As a result, the catalytic performance of the de-sulfated catalyst was slightly lower compared to the sulfated sample.

An Expanded Palette of Fluorescent COS/H2S-Releasing Donors for H2S Delivery, Detection, and In Vivo Application.

Hydrogen sulfide (H2S) is an important reactive sulfur species that is involved in many biological functions, and H2S imbalances have been indicated as a potential biomarker for various diseases. Different H2S donors have been developed to deliver H2S directly to biological systems, but few reports include donors with optical responses that allow for tracking of H2S release. Moreover, donor systems that use the same chemistry to deliver H2S across a palette of fluorescent responses remain lacking. Here we report five thiol-activated fluorescence turn-on COS/H2S donors that utilize blue, yellow, orange, red, and near infrared-emitting dyes functionalized with an H2S-releasing sulfenyl thiocarbonate scaffold. Upon treatment with thiols, each donor provides a fluorescence turn-on response (3-310-fold) and high H2S release efficiencies (>60%). Using combined electrode and fluorescence experiments, we directly correlate the measured H2S release with the fluorescence response. All donors are biocompatible and release H2S in live cell environments. In addition, we demonstrate that the NIR donor allows for imaging H2S release in live rats via subcutaneous injection of the donor loaded into an alginate gel, which to the best of our knowledge is the first in vivo tracking of H2S release from a fluorogenic donor in non-transparent organisms.