Hydrogen Sulfide Molecules Research Articles

Convective-heating thermal decomposition/digestion of peptides and proteins on surfaces

A site specific cleavage at the N-terminus of the amino acid cysteine (Cys, C) was induced on peptides and proteins deposited on surfaces via convective heating (hot air) at temperatures between 220 and 270°C for 30s. Protein and peptide samples studied were prepared as thin films in order to simulate biological tissue sections. Specifically, a stream of hot air was applied to biological samples on surfaces. The site-specific bond cleavage at Cys was found to be initiated by a loss of a hydrogen sulfide molecule from its side chain, followed by the formation of an intermediate dehydroalanine, rearrangement and water addition. This thermal decomposition process induces a cleavage of the bond between the nitrogen and α-carbon (N-terminus) of Cys. The N-terminal product, with a mass change of −1Da, shows an amidated C-terminus, while the C-terminal product has a net −33Da mass change. Thermal decomposition products of peptides and proteins were analyzed by direct insertion probe electron ionization (DIP-EI)-mass spectrometry (MS), electrospray ionization (ESI)-MS and tandem MS (MS/MS), matrix-assisted laser desorption/ionization (MALDI)-MS, and MALDI-MS/MS analyses. Molecular water was found to have little influence on the elimination of hydrogen sulfide from the intact peptide, but essential in the final cleavage step. This thermal decomposition and digestion (TDD) reaction was observed in peptide and protein samples ranging in molecular weights from 770Da to 66kDa. The cleavage specificity and speed (30s) of the convective-heating TDD method make it a viable approach for the rapid analysis of proteins in tissue or biofilm samples as part of a bottom-up in situ (or on-tissue) protein identification protocol by MALDI-MS/MS.

Study of the possibility of determining the concentration of hydrogen-sulfide molecules in the atmosphere

A numerical solution of the lidar equation was obtained for the Raman scattering of light by hydrogen-sulfide molecules in the 180° direction under daylight probing conditions to select the wavelength of laser radiation and lidar parameters as well as to determine the maximum power of Raman scattering or minimum possible time for the measurement of the concentration of hydrogen-sulfide molecules. For our Raman lidar, the optimal wavelength of laser radiation is 266 nm, which enables the detection of a concentration of 1013 cm−3 within a duration of the order of 100 s.

Adsorption and dissociation of H2S on nitrogen-doped TiO2 anatase nanoparticles: Insights from DFT computations

We have investigated the adsorption and dissociation of hydrogen sulfide (H2S) molecule on the pristine and nitrogen-doped TiO2 anatase nanoparticles using first-principles calculations in order to obtain insights into the adsorption behaviors of H2S molecules. We have investigated different adsorption geometries of H2S over the nanoparticles. We have found that the H2S adsorption is not energetically more favorable on the pristine nanoparticle surface, but H2S is preferentially adsorbed on the N-doped nanoparticles with a higher favorability in energy. H2S molecule adsorbs on the dangling oxygen, doped nitrogen and fivefold coordinated titanium sites of the TiO2 nanoparticle. The hydrogen atom in the H2S molecule forms a hydrogen bond with the surface oxygen or doped nitrogen atom of TiO2. We have reported the results of DFT calculations including the bond lengths/angles, adsorption energies, electronic density of states and molecular orbitals. Charge analysis based on Mulliken charges reveals a significant charge transfer from the molecule to the TiO2 anatase particle. The inclusion of the vdW interactions results in considerable enhancement of H2S–TiO2 interaction, thereby increasing the adsorption energies of the molecules. The N-doped nanoparticles have stronger adsorption ability than the undoped ones, indicating the higher sensing capability of N-doped nanoparticles for H2S detection. Our results suggest a great potential of N-doped TiO2 for application as a highly sensitive H2S sensor.

Catalase as a sulfide-sulfur oxido-reductase: An ancient (and modern?) regulator of reactive sulfur species (RSS)

Catalase is well-known as an antioxidant dismutating H2O2 to O2 and H2O. However, catalases evolved when metabolism was largely sulfur-based, long before O2 and reactive oxygen species (ROS) became abundant, suggesting catalase metabolizes reactive sulfide species (RSS). Here we examine catalase metabolism of H2Sn, the sulfur analog of H2O2, hydrogen sulfide (H2S) and other sulfur-bearing molecules using H2S-specific amperometric electrodes and fluorophores to measure polysulfides (H2Sn; SSP4) and ROS (dichlorofluorescein, DCF). Catalase eliminated H2Sn, but did not anaerobically generate H2S, the expected product of dismutation. Instead, catalase concentration- and oxygen-dependently metabolized H2S and in so doing acted as a sulfide oxidase with a P50 of 20mmHg. H2O2 had little effect on catalase-mediated H2S metabolism but in the presence of the catalase inhibitor, sodium azide (Az), H2O2 rapidly and efficiently expedited H2S metabolism in both normoxia and hypoxia suggesting H2O2 is an effective electron acceptor in this reaction. Unexpectedly, catalase concentration-dependently generated H2S from dithiothreitol (DTT) in both normoxia and hypoxia, concomitantly oxidizing H2S in the presence of O2. H2S production from DTT was inhibited by carbon monoxide and augmented by NADPH suggesting that catalase heme-iron is the catalytic site and that NADPH provides reducing equivalents. Catalase also generated H2S from garlic oil, diallyltrisulfide, thioredoxin and sulfur dioxide, but not from sulfite, metabisulfite, carbonyl sulfide, cysteine, cystine, glutathione or oxidized glutathione. Oxidase activity was also present in catalase from Aspergillus niger. These results show that catalase can act as either a sulfide oxidase or sulfur reductase and they suggest that these activities likely played a prominent role in sulfur metabolism during evolution and may continue do so in modern cells as well. This also appears to be the first observation of catalase reductase activity independent of peroxide dismutation.

Information system for molecular spectroscopy: 6—systematization of spectral data on deutero-substituted isotopologues of the hydrogen sulfide molecule

Properties of data published on the spectral line parameters for deutero-substituted isotopologues of the hydrogen sulfide molecule (HDS, HD34S, D2S, and D2 34S) are described. Most properties follow from the results of vacuum wavenumber quality analysis. Two applications used for the data quality analysis in W@DIS information system are described. The results of computer-based data quality analysis of vacuum wavenumbers are completed by the expert evaluation of the quality of the same data set. The rotation-vibrational transitions and energy levels of deutero-substituted isotopologues of the hydrogen sulfide molecule are imported into the database; their properties are collected in the knowledge base and available in the W@DIS information system (http://wadis.saga.iao.ru/).

Geometries of H2S⋯MI (M = Cu, Ag, Au) complexes studied by rotational spectroscopy: The effect of the metal atom.

Complexes formed between H2S and each of CuI, AgI, and AuI have been isolated and structurally characterised in the gas phase. The H2S⋯MI complexes (where M is the metal atom) are generated through laser vaporisation of a metal rod in the presence of a low concentration of H2S and CF3I in a buffer gas of argon undergoing supersonic expansion. The microwave spectra of six isotopologues of each of H2S⋯CuI, H2S⋯AgI and three isotopologues of H2S⋯AuI have been measured by chirped-pulse Fourier transform microwave spectroscopy. The spectra are interpreted to determine geometries for the complexes and to establish the values of structural parameters. The complexes have Cs symmetry at equilibrium and have a pyramidal configuration about the sulfur atom. The local C2 axis of the hydrogen sulfide molecule intersects the linear axis defined by the three heavy atoms at an angle, ϕ = 75.00(47)° for M = Cu, ϕ = 78.43(76)° for M = Ag, and ϕ = 71.587(13)° for M = Au. The trend in the molecular geometries is consistent with significant relativistic effects in the gold-containing complex. The force constant describing the interaction between the H2S and MI sub-units is determined from the measured centrifugal distortion constant, ΔJ, of each complex. Nuclear quadrupole coupling constants, χaa(M) and χaa(I) (where M denotes the metal atom), are determined for H2S⋯CuI and H2S⋯AuI for the first time.

Adsorption behaviors of hydrogen sulphide on Au(110) nanoslit array surfaces using molecular dynamics simulations

The adsorption behaviour of gas molecules on detector surfaces has a profound influence on the sensitivity of the detector. For this reason, this study used molecular dynamics simulation to explore the dynamic adsorption behaviour of hydrogen sulphide (H2S) molecules on various types of Au surfaces, including a planar Au(1 1 0) structure and three types of slit array structures. The influence of system temperature, adsorbate concentration and the slit width of nanoarrays on diffusivity, average adsorption energy and static adsorption amount were systematically examined. Simulation results indicate that the self-diffusivity of the adsorbate molecules increases with temperature but decreases with adsorbate concentration. At low concentrations (~3 mol/L), each type of Au(1 1 0) surface structure shows good capacity to adsorb all H2S molecules. With increasing concentration at 6.5 mol/L, the high concentration leads to adsorption saturation and many free H2S molecules in the planar Au(1 1 0) structure. Moreover, desorption also begins to appear on the planar structures at a temperature of 300 K (at 6.5 mol/L). The simulation results indicate that the columnar array structures with a slit width ≥5.76 Å allow molecules to swiftly spread into the slits and provide more stable adsorption sites (i.e. with a higher adsorption energy), which can effectively address the issues of high-temperature desorption and adsorption saturation. Particularly at low temperatures (≤100 K), slit structures presented a level of static adsorption of H2S that was 30% to 35 higher than that of planar structures.

Double ionization of the hydrogen sulfide molecule by electron impact: Influence of the target orientation on multiple differential cross sections

Multiple differential cross sections of double ionization of hydrogen sulfide molecule impacted by electrons are here investigated within the first Born approximation. In the initial state, the incident electron is represented by a plane wave function whereas the target is described by means of a single-center molecular wave function. In the final state, the two ejected electrons are described by Coulomb wave functions coupled by the Gamow factor, whereas the scattered electron is described by a plane wave. In this work, we analyze the role played by the molecular target orientation in the double ionization of the four outermost orbitals, namely 2b1, 5a1, 2b2 and 4a1 in considering the particular case of two electrons ejected from the same orbital. The contribution of each final state to the double ionization process is studied in terms of shape and magnitude for specific molecular orientations and for each molecular orbital we identified the mechanisms involved in the double ionization process, namely, the Shake-Off and the Two-Step 1.

Density Functional Theory (DFT) Study: Electronic Properties of Silicene under Uniaxial Strain as H<sub>2</sub>S Gas Sensor

First principle calculation is performed to investigate structural and electronic properties of strained silicene (silicon analogue of graphene) when absorbing the hydrogen sulfide molecule gas. Two configuration of silicene-H2S system, center and hollow configuration, is checked under 0% (pure), 5%, and 10% uniaxial engineering strain. We report that the silicene-H2S system in center configuration has larger binding energy compare to the silicene-H2S system in hollow configuration. The results show that H2S is physisorbed on silicene. In this work, we also find the change of band gap energy (~60 meV) is appearing when H2S interacted with silicene in center configuration, whereas the band gap energy of silicene has no change when interacted with H2S in hollow configuration.

Hydrogen sulfide gas sensor based on decorated zigzag graphene nanoribbon with copper

Adsorption of hydrogen sulfide molecules on copper decorated zigzag graphene nanoribbon has been studied theoretically. By using density functional theory, it is shown that copper creates a strong bond with hydrogen sulfide molecule. We prove that copper can form stable bonds with up to three hydrogen sulfide molecules simultaneously. Transport properties of our model have been studied using non-equilibrium green function joined with density functional theory. We demonstrate that hydrogen sulfide molecule transfers fraction of charges to the copper that lead to the alternation in the transmission spectrum. These changes are studied in detail and we confirm that hydrogen sulfide reduces the resistance of the system in low bias voltages. Our results demonstrate that hydrogen sulfide molecules can alter correlation of orbitals and make visible fluctuations in the I–V curve. These results confirm that the decorated zigzag graphene nanoribbon can be considered as a proper structure for hydrogen sulfide gas sensor and can show remarkable capabilities for industrial usage.

Thin-walled SnO₂ nanotubes functionalized with Pt and Au catalysts via the protein templating route and their selective detection of acetone and hydrogen sulfide molecules.

Bio-inspired Pt (∼2 nm) and Au (∼2.7 nm) catalysts encapsulated by a protein shell, i.e., Pt-apoferritin (Pt@AF) and Au-apoferriten (Au@AF), were synthesized via the hollow protein nanocage (apoferritin) templating route and directly functionalized on the interior and exterior walls of electrospun SnO2 nanotubes (NTs) during controlled single-nozzle electrospinning followed by high temperature calcination with heating rate control. Fast crystallization of the exterior shell and outward diffusion of the interior Sn precursors and crystallites result in the continued growth of a tubular wall, which is related to rapid heating driven Ostwald-ripening behavior. Very importantly, the Pt and Au nanoparticles (NPs) were immobilized onto thin-walled SnO2 NTs with a diameter of ∼350 nm and a shell thickness of ∼40 nm without any aggregation of catalysts due to high dispersibility, which originated from repulsive electrostatic (Coulombic) forces acting on the surface charged protein shells, leading to an enhanced catalytic effect and outstanding gas sensing properties. Pt-loaded SnO2 NTs exhibited superior acetone response (R(air)/R(gas) = 92 at 5 ppm) compared to pure SnO2 NFs (R(air)/R(gas) = 4.8 at 5 ppm) and SnO2 NTs (Rair/Rgas = 11 at 5 ppm) while Au-loaded SnO2 NTs showed a high response when exposed to hydrogen sulfide (R(air)/R(gas) = 34 at 5 ppm), offering selective gas detection with minimal cross-sensitivity against other interfering gases such as NH3, CO, NO, C6H5CH3, and C5H12. Our results provide a new insight into facile, cost-effective, and highly dispersible catalyst loading on the interior and exterior walls of hollow metal oxide NTs via simple electrospinning as a potential breath analyzer.

Adsorption of H2S molecules on non-carbonic and decorated carbonic graphenes: A van der Waals density functional study

The adsorption of hydrogen sulfide (H2S) molecules on non-carbonic (B, Al, and Ga nitride) graphene was studied using a first-principles van der Waals density functional (vdW-DF) method. For the adsorption of a single molecule, we determined the most stable configurations, equilibrium geometries, adsorption energies, and electronic properties by approaching the molecule on the surface of non-carbonic graphenes at different possible sites. The Ga nitride (GaN) graphene was more capable of H2S molecule adsorption than the other graphenes due to the higher binding energy value and shorter bonding distance between the H2S molecule and the graphene surface. Electron transfer calculations confirmed that the electronic properties of GaN graphene changes significantly compared to other graphenes after H2S molecule adsorption. The density of states results indicated a stronger physical hybridization between H2S and GaN graphene. Furthermore, co-adsorption of two H2S molecules on the GaN graphene as a single-layer/bi-layer of adsorbed molecules was examined. Finally, Al and Ga metal atoms decorated on carbonic graphene (Al- and Ga-cargraph) to investigate H2S adsorption. The adsorption of H2S on Al- and Ga-cargraph was weaker than that on the non-carbonic graphenes. Therefore, based on the obtained results, GaN graphene is promising for uses in gas sensor devices for detect H2S.

Penning ionization electron spectroscopy of hydrogen sulfide by metastable helium and neon atoms.

The dynamics of the Penning ionization of hydrogen sulfide molecules by collision with helium and metastable neon atoms, occurring in the thermal energy range, has been studied by analyzing the energy spectra of the emitted electrons obtained in our laboratory in a crossed beam experiment. These spectra are compared with the photoelectron spectra measured by using He(I) and Ne(I) photons under the same experimental conditions. In this way we obtained the negative energy shifts for the formation of H2S(+) ions in the first three accessible electronic states by He*(2(3,1)S1,0) and Ne*((3)P2,0) Penning ionization collisions: the 2b1 (X̃(2)B1) fundamental one, the first 5a1 (Ã(2)A1), and the second 2b2 (B̃(2)B2) excited states, respectively. The recorded energy shifts indicate that in the case of He* and Ne*-H2S the autoionization dynamics depends on the features of the collision complex and is mainly driven by an effective global attraction that comes from a balance among several non covalent intermolecular interaction components. This suggests that the Penning ionization should take place, in a specific range of intermolecular distances, as we have already observed in the case of Penning ionization of water molecules [Brunetti, B. G.; Candori, P.; Falcinelli, S.; Pirani, F.; Vecchiocattivi, F. J. Chem. Phys. 2013, 139, 164305-1-164305-8].

The spontaneous synchronized dance of pairs of water molecules

Molecular beam scattering experiments have been performed to study the effect of long-range anisotropic forces on the collision dynamics of two small polar molecules. The main focus of this paper is on water, but also ammonia and hydrogen sulphide molecules have been investigated, and some results will be anticipated. The intermolecular distances mainly probed are of the order of 1 nm and therefore much larger than the molecular dimensions. In particular, we have found that the natural electric field gradient, generated by different spatial orientations of the permanent electric dipoles, is able to promote the transformation of free rotations into coupled pendular states, letting the molecular partners involved in the collision complex swinging to and fro around the field direction. This long-ranged concerted motion manifested itself as large increases of the magnitude of the total integral cross section. The experimental findings and the theoretical treatment developed to shed light on the details of the process suggest that the transformation from free rotations to pendular states depends on the rotational level of both molecules, on the impact parameter, on the relative collision velocity, on the dipole moment product and occurs in the time scale of picoseconds. The consequences of this intriguing phenomenon may be important for the interpretation and, in perspective, for the control of elementary chemical and biological processes, given by polar molecules, ions, and free radicals, occurring in several environments under various conditions.

Vibration spectrum calculations of isotopic species of hydrogen sulfide using the discrete variable representation (DVR) method

In this work, a modified three-dimensional discrete variable representation (MDVR3D) program, which could be used to calculate the bound state vibration spectrum of some triatomic molecules is developed. The sine basis functions are chosen to define the DVR for the radial coordinates for this new program. Both the three-dimensional discrete variable representation (DVR3D) program and the MDVR3D program are used to calculate the vibration energy levels of the isotopic species of hydrogen sulfide (H232S, H233S, H234S, D232S, D233S, D234S, T232S, T233S, T234S). The calculated vibration energy levels from the MDVR3D program are consistent with the counterparts from the DVR3D program, which means that they are good procedures for calculating the bound state energy levels of the triatomic molecules and testing the quality of the potential energy surface (PES). The comparison of the experimental and theoretical vibration energy levels for the nine isotopic species of hydrogen sulfide molecule is made and shows good consistency. This work forms the basis for dealing with the rotational spectrum calculations and presents the first theoretical results for D233S, T232S, T233S, and T234S. Future spectrum observations are needed to compare with these new results.

Relationship between endogenous hydrogen sulfide and blood stasis syndrome based on the Qi-blood theory of chinese medicine

"Qi" and "blood" are two essential concepts in Chinese medicine (CM). As qi is intangible, the concept of qi is still controversial between CM and Western medicine. However, the endogenous hydrogen sulfide (H2S) and other gaseous signaling molecules provides a new approach for understanding the essence of qi in CM. Blood stasis syndrome is a common syndrome in CM. According to the CM theory, the incidence of blood stasis syndrome is closely correlated to the reckless movement of qi, as qi and blood are inseparable in regulating physiological functions. In recent years, more and more evidences suggest a close correlation between blood stasis syndrome and microcirculation dysfunction. In this paper, we discuss the relationship between endogenous H2S and blood stasis syndrome based on qi-blood theory of CM. We found that endogenous H2S maybe a material basis in concept of qi in CM, while dysfunctional microcirculation is the pathological basis of the blood stasis syndrome. As qi is closely associated with incidence and progression of blood stasis syndrome, endogenous H2S may play an important role in preventing and treating the blood stasis syndrome by improving the function of microcirculation.

Low Temperature Catalytic Decomposition of Hydrogen Sulfide into Hydrogen and Diatomic Gaseous Sulfur

A new catalytic reaction of hydrogen sulfide decomposition is discovered, the reaction occurs on metal catalysts in gas phase according to equation $$2{\text{H}}_{2} {\text{S}} \leftrightarrow 2{\text{H}}_{2} + {\text{S}}_{2}^{{({\text{gas}})}}$$ to produce hydrogen and gaseous diatomic sulfur, conversion of hydrogen sulfide at room temperature is close to 15 %. The thermodynamic driving force of the reaction is the formation of the chemical sulfur–sulfur bond between two hydrogen sulfide molecules adsorbed on two adjacent metal atoms in the key surface intermediate and elimination of hydrogen into gas phase. “Fingerprints” of diatomic sulfur adsorbed on the solid surfaces and dissolved in different solvents are studied. In closed vessels in adsorbed or dissolved states, this molecule is stable for a long period of time (weeks). A possible electronic structure of diatomic gaseous sulfur in the singlet state is considered. According to DFT/CASSCF calculations, energy of the singlet state of S2 molecule is over the triplet ground state energy for 10.4/14.4 kcal/mol. Some properties of gaseous diatomic sulfur are also investigated. Catalytic solid systems, both bulk and supported on porous carriers, are developed. When hydrogen sulfide is passing through the solid catalyst immersed in liquid solvent which is capable of dissolving sulfur generated, conversion of hydrogen sulfide at room temperature achieves 100 %, producing hydrogen in gas phase. This gives grounds to consider hydrogen sulfide as inexhaustible potential source of hydrogen—a very valuable chemical reagent and environmentally friendly energy product.

Influences of salinity and temperature on the stable isotopic composition of methane and hydrogen sulfide trapped in pressure-vessel hydrates

The stable isotopic composition of carbon (δ13CCH4) and hydrogen (δ2HCH4) in methane and sulfur (δ34SH2S) in hydrogen sulfide can be used to infer the source of volatile molecules encaged in gas hydrates. Differentiation of methane and hydrogen sulfide from microbial and thermal origins provides valuable information for hydrocarbon exploration and for climatic models assessing the role of gas hydrates during climate change. In astrobiological studies, δ13CCH4, δ2HCH4, and δ34SH2S values will be critical in deciphering the origin of methane and hydrogen sulfide molecules if gas hydrates are detected within the cryosphere of Mars or associated with ice-covered oceans on Europa or Enceladus. It is challenging, however, to apply isotope systematics to hydrate-forming systems due to complex influences on nucleation and decomposition under varying conditions of salinity, pressure, and temperature. Few laboratory studies have evaluated the effect of hydrate formation, on isotopic composition of free, encaged, and dissolved gas molecules. In this study, pressure-vessel hydrates were nucleated under conditions inferred for marine continental margins and terrestrial permafrost: low temperatures, moderate pressures, saturation of methane and/or hydrogen sulfide saturation, and varying concentration of sodium chloride (NaCl) and magnesium sulfate heptahydrate (MgSO4·7H2O). Methane experiments show less than 1‰ differences in values of δ13CCH4 between free and encaged molecules and up to 6.5‰ variations in values of δ2HCH4 between free and encaged molecules. In hydrogen-sulfide hydrates, δ34SH2S values show less than 4‰ differences between free and encaged molecules, but up to 14‰ differences between dissolved and free molecules and between dissolved and encaged molecules. Results presented here indicate that shifts found for free and encaged values of δ13CCH4 and δ2HCH4 are small and do not complicate interpretation of gas provenance. Conversely, in hydrate systems containing H2S molecules values of δ34SH2S need to be interpreted with caution. Although isotopic fractionation between free- and encaged-sulfur molecules is mild during hydrate formation, values of dissolved δ34SH2S are substantially fractionated and necessitate careful examination of sulfur isotopic values. Because dissolved H2S could potentially be recycled by oxidation and reduction processes during hydrate formation events, use of δ34SH2S values might complicate assessment of biosignatures for other planetary bodies.

Investigation of interaction hydrogen sulfide with (5,0) and (5,5) single-wall carbon nanotubes by density functional theory method

Herein, the interaction of hydrogen sulfide with inside and outside single-wall carbon nanotube of (5,0) and (5,5) is investigated using density functional theory at B3LYP/6-31G* level of theory in the gaseous phase by Gaussian 09. The adsorption energies, thermodynamic properties, highest occupied molecular orbital, lowest unoccupied molecular orbital, energy gaps, and partial charges of the interacting atoms are also studied during two kinds of rotation of hydrogen sulfide (H2S) molecules as vertical and horizontal to the main axes of the nanotube. For these systems, the binding energy of H2S-single-wall carbon nanotubes is low and the process is thermodynamically near-simultaneous.

Pt-decorated graphene as superior media for H2S adsorption: A first-principles study

The adsorption mechanism of hydrogen sulfide (H2S) molecules on pristine and Pt-decorated graphene sheets was studied using density functional theory calculations based on local density approximation and generalized gradient approximation methods. Our calculations show that a Pt-decorated graphene system has much higher binding energy, higher net charge transfer values and shorter connecting distances than pristine graphene due to chemisorption of the H2S molecule. Furthermore, the calculated density of states show that orbital hybridization is visible between the H2S and Pt-decorated graphene sheets, while there is no evidence for hybridization between the H2S molecule and the pristine graphene sheet. Interestingly, we find that up to seven H2S molecules can stably bind to a Pt atom on each side of the graphene sheet with desirable binding energy.