Gaseous Research Articles

Design and analysis of organic thin film gas sensor based on bottom gate elevated electrode structure

Environmental pollution especially the air pollution has proved to be a threat to all lifeforms on earth. Due to various anthropogenic activities, toxic and ozone depleting gases are released in our environment (like ammonia, Sulphur di oxide, carbon monoxide, nitrogen di oxide etc.). To check the prevalence of such gases in the atmosphere we require sensors that could accurately detect their presence in our surroundings. For the detection of these gases various type of sensors like metal oxide-based gas sensor, optical gas sensor, electro-chemical gas sensor etc. are used. Such gas sensors are largely based on inorganic electronics technology that makes them rigid, expensive, and exclusive in nature. With advent of organic electronics such sensors have become incompatible with modern electronic devices developed with organic materials like smart watches, smart fabrics etc. Also, these sensors are stationary in nature and are operational only in a fixed position. Therefore, a new organic thin film gas sensor (OTFGS) is proposed in this article that could operate at low power and could readily be integrated with the modern personal electronic gadgets like smartphones and smart watches. This will provide the mobility to the sensor and toxic gases could be detected in real time at multiple locations rather than at specific points where stationary gas sensors are installed.

Plasma-Polymerized and Iodine-Doped Polyvinyl Acetate for Volatile Organic Compound Gas Sensing Applications

Nowadays, the increased emission of hazardous volatile organic compounds (VOCs) due to rapid growth in the manufacturing industry has enforced demand for highly sensitive, selective, and stable gas sensors. Among the different types of gas sensors, we resolved issues associated with chemoresistive alcohol sensors like low selectivity, temperature instability, and long-term instability using iodine-doped polyvinyl acetate (IPVAc) films. These polymer-based chemoresistive sensors will be beneficial for low power consumption, ease of manufacture, and long-term stability owing to their simple structure and operation. The polymer films were prepared using the inductively coupled tubular plasma polymerization method. These films were doped with iodine at room temperature. The physicochemical characterization of prepared films confirmed the uniform coating of granular type morphology, iodine doping, and cubical crystal structure. The obtained maximum sensitivity was 122 and 7360 a.u. for 1000 ppm of methanol gas for polyvinyl acetate (PVAc) and IPVAc films, respectively. Also, IPVAc films demonstrated sensitivities of 5554 and 1995 a.u. for 1000 ppm of each ethanol and 2-propanol gas, respectively. IPVAc films illustrated the highest selectivity of 600 a.u. for alcohols over other VOCs like acetone, benzene, toluene, and dichloromethane. The high electronegativity of IPVAc films due to iodine doping is the key origin of the highly selective adsorption of VOCs. Additionally, the IPVAc films have stable sensitivity performance over the temperature range of 30–130 °C and repeatability over 60 days. Thus, the plasma-polymerized IPVAc films can be applied for fabricating highly selective, sensitive, and stable VOC sensing applications.

Optimization of hydrothermal liquefaction process for bio-oil products from kitchen residue under subcritical conditions

Abstract In this work, the process parameters of batch hydrothermal liquefaction of kitchen residue were optimized with the yield of bio-oil as reference, including reaction temperature, residence time and initial pressure. According to the experimental results, the bio-oil yield of kitchen residue was the highest (39.73%) under the reaction conditions of 6 MPa, 300 °C and 30 min. The elemental content and components of bio-oil were characterized by organic element analyzer and gas chromatography/mass spectrometer. The surface and structural properties of biochar were detected and analyzed by Fourier transform infrared spectrometer, scanning electron microscope and surface area and porosity analyzer.

Hollow LDH cage covering with ultra-thin MXenes veil: Integrated micro-nano structure upon heat release suppression and toxic effluents elimination for polymer

The using of epoxy resin (EP) has been compromised by its high fire hazard. In this context, MXenes nanoflakes have been preferred as flame retardant, considering its merits in suppressing heat as well as toxic gases emission. Nevertheless, it is difficult to achieve the desired flame retardancy efficiency when the MXenes dosage is low. Thus far, the development of nanostructure based on MXenes with high flame retardant capacity has been seldom investigated. In this contribution, we have designed a strongly-coupled micro-nano structure based on hollow LDH covering with ultra-thin MXenes veil (MX@H-LDH) via assembly strategy. When loading 5.0 wt% MX@H-LDH, peak heat release rate, total heat release, peak CO production rate and total CO production can be reduced by 54.6%, 37.5%, 47.4%, 63.6%, accordingly. Meanwhile, the prominence of MX@H-LDH in inhibiting the release of heat is confirmed via the comparison with previous works. The curbed toxic CO, NO and HCN releases are also discerned in gases phase analysis. Moreover, it is satisfactory to find that the using of MX@H-LDH strengthens the mechanical capability, assigned to the mechanical interlocking action. Briefly, this work can be instructive for the design of novel MXenes-based nanostructure, mining its potentials in polymer composites with high performance.

Abraham Solvation Parameter Model: Revised Predictive Expressions for Solute Transfer into Polydimethylsiloxane Based on Much Larger and Chemically Diverse Datasets

Updated Abraham model correlations are reported for the transfer of organic solutes and inorganic gases to a polydimethylsiloxane coating from both water and the gas phase based on published experimental data for more than 220 different compounds. The derived mathematical expressions back-calculate the observed partitioning behavior to within standard deviations of the residuals of 0.206 and 0.176 log units, respectively.

Metastable Defects Decrease the Fill Factor of Solar Cells

Solar cells are made from semiconductors, which inevitably include defects. The defects in Cu(In,Ga)Se${}_{2}$ (CIGS) are known to be metastable: With excitation they change character, which can have a profound impact on device function. The authors show that these metastable defects reduce the efficiency of the solar cell due to an increased diode factor. It is possible to measure this quantity directly from the bare absorber (without needing to build the entire solar cell), yielding a lower limit for the whole device. Experiments and simulations indicate that metastable defects must be reduced to increase efficiency, and not just in CIGS-based solar cells.

Cryogenic Chemistry and Quantitative Non-Thermal Desorption from Pure Methanol Ices: High-Energy Electron versus X-Ray Induced Processes.

X-Ray irradiation of interstellar ice analogues has recently been proven to induce desorption of molecules, thus being a potential source for the still-unexplained presence of gaseous organics in the coldest regions of the interstellar medium, especially in protoplanetary disks. The proposed desorption mechanism involves the Auger decay of excited molecules following soft X-ray absorption, known as X-ray induced electron-stimulated desorption (XESD). Aiming to quantify electron induced desorption in XESD, we irradiated pure methanol (CH3 OH) ices at 23 K with 505 eV electrons, to simulate the Auger electrons originating from the O 1s core absorption. Desorption yields of neutral fragments and the effective methanol depletion cross-section were quantitatively determined by mass spectrometry. We derived desorption yields in molecules per incident electron for CO, CO2 , CH3 OH, CH4 /O, H2 O, H2 CO, C2 H6 and other less abundant but more complex organic products. We obtained desorption yields remarkably similar to XESD values.

Natural gas characteristics and gas-source comparisons of the Lower Triassic Feixianguan Formation, Eastern Sichuan Basin, China

There is great controversy regarding the origin and source of natural gas in the Lower Triassic Feixianguan Formation in the Eastern Sichuan Basin. This seriously restricts the study of natural gas dynamics in the Feixianguan Formation and thus hampers natural gas exploration in the region, so further study is urgently required. Using experimental tests of natural gas composition, stable isotopes, and noble gas isotopes with gas chromatography (GC) and mass spectrometry (MS) studies of source rock and reservoir asphalt saturated hydrocarbons, the natural gas geochemical characteristics, the genetic identification and a gas-source comparison of the Feixianguan Formation were studied. Then, constrained by the thermal history, the histories of gas generation and expulsion were restored by basin simulation technology. Finally, a gas accumulation model was established for the Feixianguan Formation. The results showed that (1) the H2S-rich and H2S-poor gas reservoirs of the Feixianguan Formation are distributed on the east and west sides of the Kaijiang-Liangping trough in the Eastern Sichuan Basin, respectively. The carbon and hydrogen isotope compositions of the natural gas in the gas reservoirs are generally heavy and have typical characteristics of high-maturity dry gas reservoirs. (2) The natural gas of the Feixianguan Formation is organic thermogenic gas, which is mainly oil-type gas generated by the secondary cracking of crude oil. The gas-generating parent material is mainly type II kerogen. (3) The natural gas of the Feixianguan Formation in the Eastern Sichuan Basin was mainly generated by argillaceous source rocks of the Upper Permian Longtan Formation. (4) Natural gas accumulation occurred as follows: the paleo-structure heights were filled with crude oil in the Early Jurassic, and paleo-oil reservoirs were formed in the Feixianguan Formation; during the Middle-Late Jurassic, the paleo-oil reservoirs were cracked when the reservoir temperatures rose above 160 °C, and paleo-gas reservoirs were formed. Since the end of the Late Jurassic, the paleo-gas reservoirs have been adjusted and reformed to form the present-day natural gas reservoirs. These results provide a basis for studying natural gas accumulation dynamics of the Feixianguan Formation in the Eastern Sichuan Basin.

Formaldehyde Gas Sensing Characteristics of ZnO-TiO2 Gas Sensors

Since the increase in the emission of various Volatiles Organic Compounds, gas and formaldehyde gas have had a harmful effect on the human body, and gas sensors that can measure those gases were fabricated in this study. After Pt coating was performed on the alumina substrate, Zn seed layers were fabricated. Nanostructures were formed through sonochemical synthesis by varying the ratio of ZnO and TiO2. Thereafter, the reactivity and recovery properties were compared and evaluated according to the concentrations of formaldehyde and toluene gas. The ZnO(99%)-TiO2(1%) gas sensor showed meaningful selectivity of about 40% or more at a concentration ranging from 5 to 20 ppm (high concentration) of formaldehyde and toluene gas, and showed a low selectivity of about 5% or more for a concentration ranging from 0.1 to 1 ppm (low concentration) of formaldehyde and toluene gas. This sensor can be optimized to have a meaningful selectivity of formaldehyde gas compared to other Volatiles Organic Compounds gases by optimizing the ZnO-TiO2 nanostructure.

Experimental investigation on hydrocarbon generation of organic-rich shale with low maturity in sub- and supercritical water

Sub- and supercritical water, as solvents for organic matters, are promising for hydrocarbon generation of low maturity organic-rich shale. However, there is still no noteworthy study on the difference of dynamic hydrocarbon generation of low maturity organic-rich shale between sub- and supercritical water conditions. In this study, a non-isothermal heating reactor was used to simulate the hydrocarbon generation experiment of low maturity organic-rich shale at 360 °C, 21 MPa subcritical water and 400 °C, 25 MPa supercritical water within the range of 2–12 h. The differences of the hydrocarbon generation performance, product distribution, mineral composition and pore size distribution evolution between sub- and supercritical water condition were investigated. The results showed that the utilization degree of organic carbon and gas yield under supercritical water conditions were higher than that under subcritical water conditions at any given time within 2–12 h. The supercritical water condition had the advantage of an oil yield before 10 h, which was surpassed by subcritical water condition after 10 h. The relative content of saturated hydrocarbon and aromatic hydrocarbon were higher than resin and asphaltene under both sub- and supercritical water condition. The oil produced under subcritical water condition had more aromatic hydrocarbons. The selectivity of supercritical water for H2, CH4, C2H4 and C2H6 was higher than that of subcritical water, and the selectivity of subcritical water for CO2 was higher than that of supercritical water within the range of 0–12 h. The pyrite removing and pore expansion effects of supercritical water were greater than subcritical water. The mechanism of supercritical water to enhance the utilization degree of organic carbon mainly includes the enhancement of thermal efficiency, solubility, diffusion in terms of physical property effect, and the promotion of free radical reaction in terms of chemical property effect. We hope that the results will provide technical and theoretical support for in-situ hydrocarbon generation of low-mature organic-rich shale.

Surface Engineering of Submicron Cu(In,Ga)Se2for High-Efficient Zn(O,S)-Based Solar Cells with Lower Light Soaking Effects

Surface Engineering of Submicron Cu(In,Ga)Se₂for High-Efficient Zn(O,S)-Based Solar Cells with Lower Light Soaking Effects

R.E.A.C.T-Rapid Electro-Analytical graphitic Carbon nitride-based screening Tool for lung cancer – Case study using heptane

Early disease detection and diagnosis through breath-based chemical assessment is broadly studied as a non-invasive tool and used as a cutting-edge opportunity in health care. Breath analytics or Breathomics is based on the recognition of levels of metabolites such as Volatile Organic Compounds (VOCs) and inorganic gases in an exhaled human breath. Lung cancer, one such disease state, alters the concentrations of hydrocarbons released in breath due to oxidative stress and lipid pre-oxidation. Heptane can be utilized as a VOC biomarker for the non-invasive diagnosis of lung cancer. This work outlines the fabrication of a graphitic carbon nitride-based electrochemical sensor platform that possesses increased catalytic activity and can be used for the screening of heptane vapors in the range of 0.45–5 ppm limit of detection of 0.45 ppm with 95% confidence interval. The synthesized material is characterized and validated using various standard analytical methods. Chronoamperometry is employed as an electrochemical technique to examine the diffusion dynamics of the target analyte. We demonstrated the specific sensing responses of the system in the presence of interferants by executing a cross-reactivity study with respect to other commonly found interferants in breath. We effectively established the use of a graphitic carbon nitride-based electrochemical sensor for point-of-care screening (qualitative analysis with p < 0.05) of heptane levels by the development of a prototype device utilizing a commercial microelectronic board. We envision that the in-house fabricated modified electrode platform can aid in early screening for lung cancer, thus leading to a reduction in the mortality rate.

Experimental and theoretical EBIC analysis for grain boundary and CdS/Cu (In, Ga)Se2 heterointerface in Cu (In, Ga)Se2 solar cells

AbstractThe behavior of carriers for an electron‐beam‐induced current (EBIC) evaluation is experimentally and theoretically analyzed for the polycrystalline Cu (In, Ga)Se2 (CIGS) thin‐film solar cells. The experimental EBIC signal in‐depth profiles of the CIGS layers show four features: peaks at grain boundaries (GBs), narrowed peaks near the surface, shifted peaks near the surface, and double peaks at the GBs and surface. Operating principles for CIGS solar cell devices under electron–hole pair excitation are systematically revealed utilizing a two‐dimensional theoretical EBIC simulation: (i) The EBIC peaks at the GBs are caused by a high hole barrier, including a valence band offset (ΔEV) and a band bending at the GBs; (ii) narrowing of EBIC peaks near the surface is caused by high defect densities at the GBs, grading of a conduction band minimum, and grading of acceptor concentration (Na) along with the CIGS depth direction; (iii) a shift in EBIC peaks near the surface is caused by high donor‐like defect densities at the surface; (iv) double peaks at the GBs and surface are caused by a thick surface layer (SL) with the ΔEV and the hole barrier at GBs. These findings of the EBIC analysis will help to comprehensively understand the complex polycrystalline CIGS carrier transport mechanism in realizing the highest‐efficiency CIGS solar cells.

Development and performance evaluation of an intelligent air purifier/humidifier using fuzzy logic controller

AbstractThis study aimed to develop and implement a fuzzy logic controlled-intelligent air purifier/humidifier. The concepts of passive purification and evaporative humidification were used to build this device, and engineering ideas and theories were used to guide the development of electrical and mechanical systems. Additionally, a fuzzy logic controller was designed, built and integrated into the air purifier/humidifier device to help with its operation. It does this by analysing input signals from all the sensors (dust, volatile organic compound gas, humidity and water level) and activating the actuators (suction and blow fan). On the Arduino IDE, a C/C++ programming code was developed and uploaded onto the Arduino Uno R3 board, which houses the ATmega328P microcontroller processor. In estimating the clean air delivery rate (CADR), noise level and moisture delivery rate, the performance of the developed air purifier/humidifier was assessed. Additionally, the electrical systems’ power consumption and the fuzzy logic controller’s ease of use were each assessed. In light of the room capacity taken into consideration, the findings obtained demonstrated that the proposed air purifier/humidifier device satisfies the minimum standard requirement of a CADR of 140m3/hr. The outcome also revealed that the designed device’s noise level is lower than the typical threshold for an air purifier, which is less than 40 db. Additionally, after 68 minutes, the device raised the humidity level in a controlled area from 21% to 40%.

Ground-state stability and excitation spectrum of a one-dimensional dipolar supersolid

We study the behavior of the excitation spectrum across the quantum phase transition from a superfluid to a supersolid phase of a dipolar Bose gas confined to a one-dimensional geometry. Including the leading beyond-mean-field effects within an effective Hamiltonian, the analysis is based on Bogoliubov theory with several order parameters accounting for the superfluid as well as solid structure. We find fast convergence of the ground-state energy in the supersolid with the number of order parameters and demonstrate a stable excitation spectrum with two Goldstone modes and an amplitude mode in the low-energy regime. Our results suggest that there exists an experimentally achievable parameter regime for dysprosium atoms, where the supersolid phase exhibits a stable excitation spectrum in the thermodynamic limit and the transition into the supersolid phase is of second order driven by the roton instability.

Self-regulation of black hole accretion via jets in early protogalaxies

ABSTRACT The early growth of black holes (BHs) in high-redshift galaxies is likely feedback regulated. While radiative feedback has been extensively studied, the role of mechanical feedback has received less scrutiny to date. Here, we use high-resolution parsec-scale hydrodynamical simulations to study jet propagation and its effect on 100 M⊙ BH accretion in the dense, low-metallicity gas expected in early protogalaxies. As the jet propagates, it shocks the surrounding gas forming a jet cocoon. The cocoon consists of a rapidly cooling cold phase at the interface with the background gas and an overpressured subsonic phase of reverse shock-heated gas filling the interior. We vary the background gas density and temperature, BH feedback efficiency, and the jet model. We found that the width of the jet cocoon roughly follows a scaling derived by assuming momentum conservation in the jet-propagation direction and energy conservation in the lateral directions. Depending on the assumed gas and jet properties, the cocoon either stays elongated to large radii or isotropizes before reaching the Bondi radius, forming a nearly spherical bubble. Lower jet velocities and higher background gas densities result in self-regulation to higher momentum fluxes and elongated cocoons. In all cases, the outward cocoon momentum flux balances the inward inflowing gas momentum flux near the Bondi radius, which ultimately regulates BH accretion. The time-averaged accretion rate always remains below the Bondi rate, and exceeds the Eddington rate only if the ambient medium is dense and cold, and/or the jet is weak (low velocity and mass loading).

The Physics of Twin Boundary Termination in Cu(In, Ga)Se2 Absorbers

The grain boundaries (GBs) in the absorber of a Cu(In,Ga)(S,Se)2 (CIGS) solar cell play a vital role in its efficiency and cells with polycrystalline absorbers exhibit high conversion efficiency (&gt;23%). Previous investigations confirm that the traits of GBs in CIGS are directly connected to their composition. However, such a relationship cannot be established for twin boundaries (TBs). This is because although electron beam‐induced current (EBIC) highlights the existence of both electrically inactive and active TBs, atom probe tomography is not able to detect composition fluctuations in a very limited volume (one or two monolayers). Therefore, herein, high‐resolution scanning transmission electron microscopy at TBs to investigate their differences and correlate them with their traits is used. It is found that the electrically neutral TBs are cation–anion‐terminated boundaries, whereas the electrically beneficial TBs are cation–cation terminated. Density functional theory results show that the formation of point defects next to cation–cation TBs is more favorable compared to the case with cation–anion TBs. The presence of Cu vacancies can result in a passivated TB and a hole‐depletion region next to the cation–cation TBs, and consequently a better electron transport, as the bright contrast observed in the EBIC map suggests.

Highly Sensitive and Selective Organic Gas Sensors Based on Nitrided ZSM-5 Zeolite

For next-generation gas sensors, conductive polymers have strong potential for overcoming the existing deficiencies of conventional inorganic sensors based on metallic oxides. However, the signal of organic gas sensors is inferior to that of inorganic metal oxide gas sensors because of organic gas sensors' poor charge carrier transport. Herein, the combination of an organic transistor-type gas sensor and a zeolite with strong gas-adsorbing properties is proposed and experimentally demonstrated. Among the various investigated zeolites, ZSM-5 with ∼5.5 Å pore openings enhanced the adsorption for small gas molecules when combined with a polymer active layer, where it provided a pathway for gas molecules to penetrate the zeolite channels. Moreover, nitrided ZSM-5 (N-ZSM-5) enhanced the sensing performance of NO2 molecules selectively because N in the N-ZSM-5 framework strongly interacted with NO2 molecules. These results open the possibility for zeolite-modified organic gas sensors that selectively adsorb target gas molecules via heteroatoms substituted into the zeolite framework.

Machine Learning-Assisted Volatile Organic Compound Gas Classification Based on Polarized Mixed-Potential Gas Sensors

The performance of electrochemical gas sensors depends on the reactions at the three-phase boundary. In this work, a mixed-potential gas sensor containing a counter electrode, a reference electrode, and a sensitive electrode was constructed. By applying a bias voltage to the counter electrode, the three-phase boundary can be polarized. The polarization state of the three-phase boundary determined the gas-sensitive performance. Taking 100 ppm ethanol vapor as an example, by regulating the polarization state of the three-phase boundary, the response value of the sensor can be adjusted from -170 to 40 mV, and the sensitivity can be controlled from -126.4 to 42.6 mV/decade. The working temperature of the sensor can be reduced after polarizing the three-phase boundary, lowering the power consumption from 1.14 to 0.625 W. The sensor also showed good stability and short response-recovery time (3 s). Based on this sensor, the Random Forest algorithm reached 99% accuracy in identifying the kind of VOC vapors. This accuracy was made possible by the ability to generate several signals concurrently. The above gas-sensitive performance improvements were due to the polarized three-phase boundary.

Genetic relationship between the Maoping Pb-Zn deposit and paleo-oil reservoir in the northern Yunnan-Guizhou depression: Evidence from bitumen trace elements and the in-situ sulfur isotope of pyrite associated with bitumen

The coexistence of numerous Mississippi Valley-type (MVT) Pb-Zn deposits and oil/gas reservoirs in the world demonstrates that a close genetic link between them. The northern Yunnan–Guizhou depression (NYGD) is a tectonic unit containing Pb–Zn deposits, paleo-oil reservoirs and shale gas. However, previous studies on the relationship between hydrocarbon accumulation and Pb–Zn mineralization have been ignored. The Maoping Pb–Zn deposit is a large-sized MVT deposit in the NYGD where a large amount of solid bitumen (i.e., a paleo-oil reservoir) occurs, and it is an ideal area to study the relationship between hydrocarbon accumulation and lead–zinc mineralization. In this paper, the bitumen and pyrite associated with bitumen from the Xujiazhai (discovered in this study) and Xiaocaoba paleo-oil reservoirs and the Maoping Pb–Zn deposit are researched. Geological observation has revealed that bitumen occurs in dissolution pores, fractures and intercrystalline pores in dolomite of the Upper Devonian and Carboniferous. The bitumen from Xujiazhai, Maoping and Xiaocaoba with high and similar Raman equivalent reflectance (RmcRo%) indicates they are in over-mature level and may be derived from the cracking of early-accumulated crude oils. The bitumen in the Xujiazhai paleo-oil reservoir and Maoping deposit has an abundant Pb and Zn content, indicating petroleum liquids may act as the transporting agents of metallogenic metal elements, carrying them to sites where mineralization may take place. The source rocks may have provided not only the oil for paleo-oil/gas reservoirs, but also a portion of ore metals for the Pb-Zn mineralization. The bacterial sulfate reduction (BSR) and thermochemical sulfate reduction (TSR) processes were recorded by the pyrite in the paleo-oil reservoir, which was consistent with the mechanism of reduced sulfur formation in the Maoping deposit. In addition, the large negative (−27.7‰ to −5.7‰) and positive (.9‰ to 19.2‰) δ34S values of the pyrite associated with the bitumen in the paleo-oil reservoir were similar to those of the sulfide in the Maoping deposit. We believe that the formation and evolution of the paleo-oil reservoirs are closely related to the metallogenic process of the Maoping Pb–Zn deposit, and the sulfides in them have the same sulfur source and formation mechanism as reduced sulfur. BSR phenomena could occur in prior to migration of the hydrocarbons into the reservoir or low mature oil stage in paleo-oil reservoir; a small amount of H2SBSR was combined with metal ions in ancient oil reservoirs and deposits to form early subhedral, xenomorphic granular, fine-grained strawberry aggregate pyrite and/or gelatinous sphalerite. The paleo-gas reservoir formed by the evolution of the paleo-oil reservoir in the main metallogenic period potentially participated in the mineralization; that is, organic gas acted as a reducing agent and transformed SO42− in the upper Devonian Zaige Formation gypsum strata on the periphery of the Maoping lead–zinc mining area into H2STSR through TSR, providing reduced sulfur and creating the environmental conditions for mineralization. During or after the transformation of the paleo-oil reservoir to a paleo-gas reservoir, the decoupling of metals and organic complexes may have provided the ore metals for mineralization. Massive sulfide precipitation may have occurred during or after the paleo-oil reservoir cracked into the paleo-gas reservoir.