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DOE OSTI2026

Power conversion in SnS photocathodes made by electrochemical growth is limited by recombination at (002) buried facets

Herzenbergite α-SnS is a promising p-type semiconductor for photovoltaic and solar fuel applications, but current devices are plagued by substantial photovoltage losses. Here we use vibrating Kelvin probe surface photovoltage for the first time to study the recombination losses in microcrystalline SnS photoelectrodes. α-SnS films of varied crystal orientation, size, and shape are obtained by electrochemical growth from aqueous tin( II ) chloride and sodium thiosulfate solutions near room temperature. After application of a CdS passivation layer, the films function as photocathodes for the methylviologen reduction reaction. Photoelectrochemical and surface photovoltage measurements reveal that the performance of these devices is sensitively controlled by mainly the SnS crystal orientation and to a lesser extent by the grain size. For example, the highest charge recombination rates of 8.97 × 10 14 s −1 cm −2 and lowest photocurrent (0.73 mA cm −2 ) and lowest photovoltage (0.12 V) occur for SnS films containing 500 nm crystals with irregular shapes and SnS lattices tilted away from the (001) orientation. On the other hand, the best performance (1.62 mA cm −2 , 0.16 V, 3.32 × 10 12 s −1 cm −2 ) is seen for 1100 nm fully (001) oriented SnS nanoplates. Furthermore, these findings agree with improved charge carrier mobility in the 001 direction and they also show that charge recombination in SnS films occurs mainly at dangling Sn–S bonds at buried (002) facets. Such buried interfaces need to be suppressed for optimized solar energy conversion with SnS.

Najaf, Zainab [University of California, Davis, CA↗

DOE OSTI2024

Design & Assembly of Atomically-Precise Quantum Materials & Devices (Final Report)

Atomic-layer honeycomb materials (Xene, where “X” may stand for a number of different elements) are a promising platform for new quantum states. When X is a heavier element such as tin (Sn) or bismuth (Bi), the edges of the honeycomb may conduct electron charge or spin without resistance - an effect that could persist up to room temperature in some cases. The type of edge states, and their robustness at room temperature, depend sensitively on (a) the substrate material that the Xene is sitting on; (b) out-of-plane buckling of the honeycomb structure; (c) the pattern of atoms or molecules sitting atop the honeycomb. This sensitivity suggests that Xene edge states could be tuned and rearranged to construct nanoscale electronic or spintronic devices. We report on theoretical progress in modeling the assembly and structure of Xenes, and their underlying substrates and overlaying atoms. Specifically, we model the stability of Sn atoms forming a single atomic layer (“stanene”), the stability and phase transitions

36 MATERIALS SCIENCE↗

DOE OSTI2022

Free Energy Dependencies for Interfacial Electron Transfer from Tin-Doped Indium Oxide (ITO) to Molecular Photoredox Catalysts

John B. Goodenough proposed that interfacial electron transfer kinetics from main group metal oxides should be fundamentally different from that of transition metal oxides, an expectation that has not been widely tested. Herein, the kinetics for interfacial electron transfer from mesoporous transparent conductive oxide Tin-doped Indium Oxide (ITO) to four photoredox catalysts (PCs) were characterized in acetonitrile electrolytes. The photocatalysts had the form: [Ru(4,4ʹ-R 2 -2,2′-bipyridine) 2 (4,4ʹ-(PO 3 H 2 ) 2 -2,2′-bipyridine)] 2+ , where R was H, methoxy, tert -butyl, and Br. The impact of the surface binding group was characterized with [Ru(2,2′-bipyridine) 2 (4,4ʹ-(CO 2 H) 2 -bpy)] 2+ . The interfacial electron transfer reaction ITO(e − )∣PC + → ITO∣PC was quantified by nanosecond absorption spectroscopy as a function of the applied potential (and hence ‒Δ G °). Specific conditions of applied potential were identified where the kinetics were sensitive to the incident irradiance. A layer-by-layer method was used to insert ionic methylene bridge(s) between the PC and the oxide surface. Marcus-Gerischer analysis of the kinetic data indicates non-adiabatic interfacial electron transfer with total reorganization energies that increase when bridges were placed between the photocatalyst and the ITO surface.

Bangle, Rachel E.↗

NASA NTRS1975

SEASAT economic assessment. Volume 4: Ocean mining case study and generalization

The results of a study of the weather sensitive features of near shore and deep water ocean mining industries are described. Problems with the evaluation of economic benefits for the deep water ocean mining industry are attributed to the relative immaturity and highly proprietary nature of the industry. Case studies on the gold industry, diamond industry, tin industry and sand and gravel industry are cited.

Source record↗

DOE OSTI2025

Mitigating humidity interference in chemiresistive hydrogen sensors through hydrophobic surface functionalization

Chemiresistive gas sensors based on semiconductor metal oxides, such as tin dioxide (SnO₂), are indispensable for detecting and monitoring toxic gases and pollutants, making them critical components in industrial and environmental applications. To enhance their performance, the metal oxides are loaded with noble metals such as palladium (Pd). However, ambient humidity poses a significant challenge to their performance. The presence of adsorbed water molecules on the oxide surface can considerably impair sensor sensitivity and overall performance. To address this issue, in this paper, we report on the application of an ultrathin, hydrophobic layer of hexamethyldisilazane to the surface of a Pd/SnO 2 sensor. This study investigates the influence of hydrophobic surface modifications on the metal oxide interface, focusing on their impact on sensor sensitivity and selectivity. The resulting sensor exhibits superior hydrogen sensing capabilities, operating effectively at low temperatures even in high humidity environments. Furthermore, the hydrophobic modification reduces the sensor’s susceptibility to interfering gases, thus enhancing its selectivity. The combined enhancements in moisture resistance and selectivity achieved through HMDS surface modification, along with the superior sensitivity of Pd/SnO₂ sensors, facilitate the development of gas sensors with enhanced humidity tolerance and broader applications.

Chemiresistive gas sensors↗

NASA NTRS2011

Fabrication method for a room temperature hydrogen sensor

A sensor for selectively determining the presence and measuring the amount of hydrogen in the vicinity of the sensor. The sensor comprises a MEMS device coated with a nanostructured thin film of indium oxide doped tin oxide with an over layer of nanostructured barium cerate with platinum catalyst nanoparticles. Initial exposure to a UV light source, at room temperature, causes burning of organic residues present on the sensor surface and provides a clean surface for sensing hydrogen at room temperature. A giant room temperature hydrogen sensitivity is observed after making the UV source off. The hydrogen sensor of the invention can be usefully employed for the detection of hydrogen in an environment susceptible to the incursion or generation of hydrogen and may be conveniently used at room temperature.

Seal, Sudipta↗

DOE OSTI2020

Water-Stable 1D Hybrid Tin(II) Iodide Emits Broad Light with 36% Photoluminescence Quantum Efficiency

The optical and light emission properties of tin and lead halide perovskites are remarkable because of the robust room-temperature (RT) performance, broad wavelength tunability, high efficiency, and good quenching resistance to defects. These highly desirable attributes promise to transform current light-emitting devices, phosphors, and lasers. One disadvantage in most of these materials is the sensitivity to moisture. Here, we report a new air-stable one-dimensional (1D) hybrid lead-free halide material (DAO)Sn 2 I 6 (DAO, 1,8-octyldiammonium) that is resistant to water for more than 15 h. The material exhibits a sharp optical absorption edge at 2.70 eV and a strong broad orange light emission centered at 634 nm, with a full width at half-maximum (fwhm) of 142 nm (0.44 eV). The emission has a long photoluminescence (PL) lifetime of 582 ns, while the intensity is constant over a very broad temperature range (145–415 K) with a photoluminescence quantum yield (PLQY) of at least 20.3% at RT. Above 415 K the material undergoes a structural phase transition from monoclinic (C2/c) to orthorhombic (Ibam) accompanied by a red shift in the band gap and a quench in the photoluminescence emission. Density functional theory calculations support the trend in the optical properties and the 1D electronic nature of the structure, where the calculated carrier effective masses along the inorganic chain are significantly lower than those perpendicular to the chain. As a result, thin films of the compound readily fabricated from solutions exhibit the same optical properties, but with improved PLQY of 36%, for a 60 nm thick film, among the highest reported for lead-free low-dimensional 2D and 1D perovskites and metal halides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Sorption‐Induced Fiber Optic Plasmonic Gas Sensing via Small Grazing Angle of Incidence

Abstract Sensing technologies based on plasmonic nanomaterials are of interest for various chemical, biological, environmental, and medical applications. In this work, an incorporation strategy of colloidal plasmonic nanoparticles (pNPs) in microporous polymer for realizing distinct sorption‐induced plasmonic sensing is reported. This approach is demonstrated by introducing tin‐doped indium oxide pNPs into a polymer of intrinsic microporosity (PIM‐1). The composite film (pNPs‐polymer) provides distinct and tunable optical features on the fiber optic (FO) platform that can be used as a signal transducer for gas sensing (e.g., CO 2 ) under atmospheric conditions. The resulting pNPs‐polymer composite demonstrates high sensitivity response on FO in the evanescent field configuration, provided by the dramatic response of modes above the total‐internal‐reflection angle. Furthermore, by varying the pNPs content in the polymer matrix, the optical behavior of the pNPs‐polymer composite film can be tuned to affect the operational wavelength by over several hundred nanometers and the sensitivity of the sensor in the near‐infrared range. It is also shown that the pNPs‐polymer composite film exhibits remarkable stability over a period of more than 10 months by mitigating the physical aging issue of the polymer.

Kim, Ki‐Joong↗

DOE OSTI2023

Ordered porous RGO/SnO 2 thin films for ultrasensitive humidity detection

In this work, ordered porous thin films of reduced graphene oxide and tin oxide (rGO/SnO 2 ) were synthesized by a polystyrene sphere monolayer colloidal crystal template method, and their gas-sensing properties were systematically studied. The formed amorphous SnO 2 and partially reduced graphene oxide were analyzed using several complementary material characterization techniques. Further, the results show that the incorporation of rGO significantly improved the humidity sensitivity and the electrical conductivity of the sensor relative to the pristine SnO 2 thin film. Fast response time and excellent selectivity towards humidity were also achieved for the rGO/SnO 2 composite film. The long-term stability of the rGO/SnO 2 sensor was confirmed by comparing its performance to a commercial humidity sensor. The enhanced sensor performance is attributed to the synergistic effects of the incorporation of rGO and the ordered porous structure of the composite film.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1990

Mechanistic studies of the CO-oxidation reaction on catalysts for use in long-life CO2 lasers

The catalytic recombination of carbon monoxide and oxygen was studied under conditions expected to be present in a sealed E-beam CO2 laser system. These conditions are typically a gas inlet temperature of 60 C, a substoichiometric CO/O2 ratio of ca. 2.5/1 with an oxygen feed rate of ca. 5 micromoles/s, a carrier gas comprising He, N2 and CO2 in the ratio of 3:2:1, near atmospheric pressure and a gas velocity of 4 m/s. Heterogeneous catalysts, based on precious metal supported on tin oxide, have been coated onto ceramic monoliths and tested for catalytic activity and stability after a reduction/passivation step. Two catalyst systems have been chosen. These are Pt/Pd/SnO2 and Pt/Ru/SnO2. Under the conditions described above, a characteristic decline in catalytic activity is apparent for both systems, and exit gas temperature has been recognized as a sensitive parameter by which to monitor the activity changes. A semilogarithmic plot of exit temperature as a function of time has revealed two distinct processes connected with the decline in activity: one process is associated with reduction of the oxidized precious metal (at Site A), whilst the other is related to the formation and approach to steady-state of an active site at the metal/support interface (Site B).

Dawood, Talat↗

DOE OSTI2020

Understanding the transport and break up of reactive ejecta

This manuscript investigates reactive- versus hydrodynamic-breakup processes of ejecta. For this paper, the reactive metal is cerium (Ce) and the nonreactive metal is tin (Sn), the nonreactive gas is helium (He) and the reactive gas is deuterium (D 2 ) or hydrogen (H 2 ). Experiments were performed in vacuum and the reactive- and nonreactive-gases at various pressures, where we endeavored to match the post-shock gas densities to differentiate between reactive- versus hydrodynamic-breakup processes. Hydrodynamic breakup sensitively links to the Weber number (gas density, liquid fragment diameter, surface tension, and the square of the relative velocity between the fragment and the gas), whereas reactive breakup links to the reactive dynamics which includes two processes. In one case the reactive metal breaks up into smaller fragments as rapidly as the reaction rate, and in the other a crust grows on the liquid fragments as the reactions occur, a diffusion limited process. In the latter case, the particle diameters increase with time as the crust grows. In this process, which is indicated by the data, particles breakup as the CeD 2 loses strength with increasing temperature, leaving an exponentially increasing diameter.

36 MATERIALS SCIENCE↗

DOE OSTI2026

Mass radius and D-term of atomic nuclei in relativistic mean field theory

Based on relativistic mean field theory for atomic nuclei, we compute the mass radius and other radii associated with the energy momentum tensor for dozens of spin-0 nuclei across the nuclear chart. We also compute the D-term of these nuclei, the forward limit of the gravitational form factor 𝐷⁡(𝑡=0)=𝐷. The dependence on the neutron number 𝑁 is systematically studied for calcium (Ca), nickel (Ni), zirconium (Zr), tin (Sn), and lead (Pb) isotopes. Remarkably, |𝐷| does not monotonically increase with 𝑁. Instead, it exhibits local maxima and minima when 𝑁 equals a magic number and even a submagic number. This results in characteristic kinks in the mass, scalar, tensor, and shear radii of these isotopes. Our work for the first time elucidates the strong sensitivity of the various mechanical properties of nuclei to the nuclear shell structure.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2022

High Accuracy Indicators of Androgen Suppression Therapy Failure for Prostate Cancer—A Modeling Study

Prostate cancer is a serious public health concern in the United States. The primary obstacle to effective long-term management for prostate cancer patients is the eventual development of treatment resistance. Due to the uniquely chaotic nature of the neoplastic genome, it is difficult to determine the evolution of tumor composition over the course of treatment. Hence, a drug is often applied continuously past the point of effectiveness, thereby losing any potential treatment combination with that drug permanently to resistance. If a clinician is aware of the timing of resistance to a particular drug, then they may have a crucial opportunity to adjust the treatment to retain the drug’s usefulness in a potential treatment combination or strategy. In this study, we investigate new methods of predicting treatment failure due to treatment resistance using a novel mechanistic model built on an evolutionary interpretation of Droop cell quota theory. We analyze our proposed methods using patient PSA and androgen data from a clinical trial of intermittent treatment with androgen deprivation therapy. Our results produce two indicators of treatment failure. The first indicator, proposed from the evolutionary nature of the cancer population, is calculated using our mathematical model with a predictive accuracy of 87.3% (sensitivity: 96.1%, specificity: 65%). The second indicator, conjectured from the implication of the first indicator, is calculated directly from serum androgen and PSA data with a predictive accuracy of 88.7% (sensitivity: 90.2%, specificity: 85%). Our results demonstrate the potential and feasibility of using an evolutionary tumor dynamics model in combination with the appropriate data to aid in the adaptive management of prostate cancer.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1983

Determination of physical and chemical states of lubricants in concentrated contacts, part 3

Solid and liquid thin films were analyzed by infrared emission Fourier microspectrophotometry. The apparatus used is a commercial absorption instrument modified to an emission instrument, comprising a rotating polarizing device, a miniature blackbody temperature reference adjustable in temperature and radiant flux and a microscope lens with a high numerical aperture in the entrance system for increased sensitivity and resolution. Studies of lubricant behavior in a simulated ball bearing showed the alignment of the fluid molecules in the Hertzian area. Polyphenyl ether plus 1% 1,1,2-trichloroethane (TCE) required lower shear rates for the same degree of alignment than without TCE. The experiment was run with 440 C stainless steel balls coated with TiN, a chemically inert material. In both cases, the alignment was strongly influenced by the presence of TCE. The results showed (1) the dependence of alignment of fluid molecules on flow and not on adsorption at metallic surfaces, (2) phase separation between lubricant and additive under high pressure which results in two phase flow and (3) reduction in traction of torque transmitting (traction) fluids.

Lauer, J. L.↗

DOE OSTI2025

Linear Dichroism of the Optical Properties of SnS and SnSe Van der Waals Crystals

Abstract Tin monochalcogenides SnS and SnSe, belonging to a family of Van der Waals crystals isoelectronic to black phosphorus, are known as environmentally friendly materials promising for thermoelectric conversion applications. However, they exhibit other desired functionalities, such as intrinsic linear dichroism of the optical and electronic properties originating from strongly anisotropic orthorhombic crystal structures. This property makes them perfect candidates for polarization‐sensitive photodetectors working in near‐infrared spectral range. A comprehensive study of the SnS and SnSe crystals is presented, performed by means of optical spectroscopy and photoemission spectroscopy, supported by ab initio calculations. The studies reveal the high sensitivity of the optical response of both materials to the incident light polarization, which is interpreted in terms of the electronic band dispersion and orbital composition of the electronic bands, dictating the selection rules. From the photoemission investigation the ionization potential, electron affinity and work function are determined, which are parameters crucial for the design of devices based on semiconductor heterostructures.

Chemistry↗

NASA NTRS2001

Real-time measurements of endogenous CO production from vascular cells using an ultrasensitive laser sensor

Carbon monoxide (CO) has been implicated as a biological messenger molecule analogous to nitric oxide. A compact gas sensor based on a midinfrared laser absorption spectroscopy was developed for direct and real-time measurement of trace levels (in approximate pmol) of CO release by vascular cells. The midinfrared light is generated by difference frequency mixing of two nearinfrared lasers in a nonlinear optical crystal. A strong infrared absorption line of CO (4.61 microm) is chosen for convenient CO detection without interference from other gas species. The generation of CO from cultured vascular smooth muscle cells was detected every 20 s without any chemical modification to the CO. The sensitivity of the sensor reached 6.9 pmol CO. CO synthesis was measured from untreated control cells (0.25 nmol per 10(7) cells/h), sodium nitroprusside-treated cells (0.29 nmol per 10(7) cells/h), and hemin-treated cells (0.49 nmol per 10(7) cells/h). The sensor also detected decreases in CO production after the addition of the heme oxygenase (HO) inhibitor tin protoporphyrin-IX (from 0.49 to 0.02 nmol per 10(7) cells/h) and increases after the administration of the HO substrate hemin (from 0.27 to 0.64 nmol per 10(7) cells/h). These results demonstrate that midinfrared laser absorption spectroscopy is a useful technique for the noninvasive and real-time detection of trace levels of CO from biological tissues.

Non-NASA Center↗

DOE OSTI2026

Interfacial Charge Transfer Pathways in Photoelectrochemical H 2 Evolution by a Single-Component Molecular Catalyst on a Conductive Metal Oxide

Dye-sensitized photoelectrosynthesis cells traditionally combine a photosensitizing dye to harvest light and a catalyst to generate chemical fuels on a semiconductor. Here, in this work, a photoactive catalyst capable of both light absorption and fuel formation, [Cp*Ir(4,4′-Y 2 -bpy)Cl][Cl] (Cp* = pentamethylcyclopentadienyl, bpy = 2,2′-bipyridine, Y = CH 2 PO 3 H 2 ), is anchored to a mesoporous tin-doped indium oxide (ITO) electrode and facilitates photoelectrochemical H 2 evolution in water without the need for additional photosensitizers or sacrificial reductants. Spectroelectrochemistry indicates a single-site H 2 evolution mechanism involving charge injection to ITO, in contrast to the bimetallic mechanism observed in solution. Cyclic voltammetry and variable-potential chronoamperometry under illumination probe competing pathways via interfacial electron transfer between the Ir hydride excited state and the conductive ITO electrode. A Marcus theory framework provides reorganization energies for competing interfacial electron transfer pathways from potential-dependent quantum yield measurements. The light-driven H 2 evolution catalysis on conducting oxide proceeds with high Faradaic efficiency and current densities comparable to photoelectrodes utilizing p-type semiconductors. By uncovering the principal electron transfer pathways that govern photocatalytic efficiency, this study establishes design principles for hybrid molecular photoelectrocatalysts.

catalysts↗

DOE OSTI2019

Origin of Broad-Band Emission and Impact of Structural Dimensionality in Tin-Alloyed Ruddlesden–Popper Hybrid Lead Iodide Perovskites

Hybrid organic-inorganic lead halide perovskites have shown promising results as active layers in light-emitting diodes, typically utilizing the near-monochromatic, free exciton emission. Some perovskite compounds, however, show broad-band emission that is more intense than the free exciton counterpart. In this study, we show that the light emission properties of Ruddlesden-Popper hybrid perovskites PEA 2 MA n-1 Pb n I 3n+1 (PEA = phenethylammonium, MA = methylammonium) can be tuned by Sn alloying and are highly sensitive to Sn %. With increasing dimensionality, the broad-band emission quantum yield decreases drastically, from 23% in n = 1 to <1% for the n = 3 compound. Using density functional theory calculations and transient reflectance spectroscopy, the broad emission is identified as originating from self-trapped excitons. A dynamic picture of the formation process is also presented, for which ultrafast (<5 ps) hole-trapping at the Sn site is the first step, followed by electron localization from Coulombic interaction. These findings are particularly valuable for designing perovskite materials with intense room-temperature broad-band emission for solid-state lighting applications.

14 SOLAR ENERGY↗