X-ray Photoemission Spectroscopy Research Articles

Efficient nitrophenol reduction with Noria-GO nanocomposite decorated with Pd–Cu nanoparticles

We report a facile approach to synthesize Pd–Cu nanoparticles immobilized on a Noria-GO nanocomposite for efficient nitrophenol reduction. The unique architecture of the Noria and the hydrophilic nature of GO contribute to the improved performance and structure of the resulting nanocomposite. The simple sol-immobilization approach employed NaBH4 as a reductant and polyvinyl alcohol as a capping agent to evenly decorate small Pd–Cu nanoparticles with a diameter of 1.4 nm on the Noria-GO surface. The prepared Pd–Cu@Noria-GO nanocomposite was utilized as a nanocatalyst in converting of nitrophenol to aminophenol using NaBH4 solution. Our Pd–Cu@Noria-GO nanocomposite exhibited superior catalytic efficacy with large conversion percentages, Kapp, and KAF values of 95%, 0.225 min−1, and 225 min−1g−1, respectively. X-ray photoemission spectroscopy confirmed the oxidation state of the prepared nanoparticles, and TEM findings demonstrated the homogenous decoration of Pd–Cu NPs on the Noria-GO surface. Additionally, the durability of the Pd–Cu@Noria-GO nanocomposite shown its potential as a robust and promising material for remediating organic contaminants. Our results indicate that Pd–Cu@Noria-GO nanocomposite can be an effective and sustainable approach for mitigating the hazards associated with nitrophenols.

Investigation of iron oxide shell and iron core in magnetically-assisted synthetized wire-like nanochains

The zerovalent iron (Fe0) nanomaterials tend to be spontaneously oxidized in the presence of oxygen. This leads to the formation of interface composed of iron core and thin iron oxide shell. These structures are frequently observed with transmission electron microscope but, at the same time, it is hard to determine the precise structural and chemical composition of oxide shell. This feature is very important for possible applications of Fe0 nanostructures. Hence, the present work aims to deliver more detailed insights in this topic. The investigations are performed for the iron nanochains prepared in the magnetic-field-induce reduction of FeCl3 by NaBH4. The high-resolution transmission electron microscopy, electron energy loss spectroscopy, and x-ray photoemission spectroscopy confirm that the iron nanochains are covered by very thin oxide layer not exceeding over 3 nm. Moreover, the detailed XPS analyses of O 1s and Fe 2p lines indicate that the iron oxide shell reveals Fe3O4 nature. Moreover, this work demonstrated that some by-products of the reaction containing boron are presented in the sample even after a removal of the thin iron oxide shell by Ar+ treatment.

Sulfur Impurities in COx Feed Gases of Solid Oxide Cells: Effect on Degradation and Removal Strategies

High-temperature solid oxide cells (SOC) offer unrivaled Faradaic and energetic efficiencies for carbon dioxide electrolysis. However, it is yet unclear which contaminant level in carbon monoxide and carbon dioxide feed gases are tolerable to achieve low degradation rates. In this work, electrolyte-supported cells (ESC) with Ni/Gadolinia-doped ceria (Ni/CGO) fuel electrodes were exposed to CO/CO2 gas mixtures at open circuit voltage. The resistance evolution over time was monitored by means of electrochemical impedance spectroscopy. With this approach it is shown that a degradation over times of up to 96 h occurs. X-ray photoemission spectroscopy (XPS) and high-resolution secondary ion mass spectrometry (SIMS) imaging techniques were used to show that the degradation is related to sulfur impurities on the electrode surface. The results demonstrate the importance of feed gas purity for the commercialization of high-temperature CO2 electrolysis.

Room-temperature coating of Mn3O4–2D material (graphene and MoS2) nanocomposites for improving oxygen evolution reaction kinetics

Two-dimensional nanomaterials such as graphene nanosheets and molybdenum disulfide nanoflakes were easily hybridized with spinel Mn3O4 in a single deposition process at low temperature by a facile kinetic spray approach under low vacuum conditions using a nano-particle deposition system. The heterostructured Mn3O4–2D hybrid nanocomposites (NCs) were utilized to enhance the reaction kinetics of oxygen evolution. Hybrid NCs of Mn3O4 with MoS2 and graphene showed nanoflakes and nanosheet morphologies, respectively. The synergy improvement in nanocomposites of Mn3O4-graphene nanosheets and Mn3O4−MoS2 nanoflakes was examined by x-ray photoemission spectroscopy and analysis of Raman spectra that results in a decrease in OER overpotential to 289 mV at 10 mA⋅cm−2 for Mn3O4-graphene nanosheets and 295 mV for Mn3O4−MoS2 nanoflakes. The estimated Tafel slope strongly decreased from 88 mV⋅dec−1of pure Mn3O4 nanorods to around 44 mV⋅dec−1 for hybrid NCs. This behavior indicates improved charge transfer kinetics due to the decrease in charge transfer resistance. Furthermore, all fabricated nanostructure electrocatalysts exhibited very good stability for prolonged galvanostatic polarization up to 50 h.

Theoretical Investigation of Localized- and Itinerant Character of 4f Electron in Ce Intermetallics by Means of 3d-4f Resonant Inelastic X-ray Scattering

In order to show characteristic features in core-level spectroscopy, reflecting the localized- or itinerant nature of 4f electrons in Ce intermetallics, 3d x-ray photoemission spectroscopy, 3d x-ray absorption spectroscopy and 3d-4f resonant inelastic x-ray scattering (RIXS) are theoretically investigated for CeIn3 and CeSn3 with the AuCu3-type crystal structure. In this study, considering energy-band effects based on first-principles calculation within local density approximation, we employ an impurity Anderson model with full multiplet coupling. Moreover, in order to make a quantitative discussion, the basis configurations describing electron–hole pair creation are also included in the calculation within the configuration interaction scheme, which have been often neglected as a first approximation in previous studies. By comparing the calculated results for CeIn3 and CeSn3, we find two advantages of 3d-4f RIXS for a quantitative investigation of Ce intermetallics: (i) we can observe directly a binding energy in Kondo singlet formation by choosing proper polarization geometry of incident photons, and (ii) we can investigate an itinerant component related to Kondo singlet formation of Ce intermetallics by adjusting energy and polarization of incident photons.

Versatile procedure for the correction of non-isochromatism in XPEEM spectroscopic imaging

Non-isochromatism in X-ray PhotoEmission Electron Microscopy (XPEEM) may result in unwanted artifacts especially when working with large field of views. The lack of isochromatism of XPEEM images may result from multiple factors, for instance the energy dispersion of the X-rays on the sample or the effect of one or more dispersive elements in the electron optics of the microscope, or the combination of both. In practice, the photon energy or the electron kinetic energy may vary across the image, complicating image interpretation and analysis. The effect becomes severe when imaging at low magnification upon irradiation with high energy photons. Such imaging demands for a large X-ray illuminating spot size usually achieved by opening the exit slit of the X-ray monochromator while reducing the monochromaticity of the irradiating light. However, we show that the effect is linear and can be fully removed. A versatile correction procedure is presented which leads to true monochromatic photoelectron images at improved signal-to-noise ratio. XPEEM data recorded at the nanospectroscopy beamline of the Elettra synchrotron radiation facility illustrate the working principle of the procedure. Also, reciprocal space XPEEM data such as angle-resolved photoelectron spectroscopy (ARPES) momentum plots suffer from linear energy dispersion artifacts which can be corrected in a similar way. Representative data acquired from graphene synthesized on copper by chemical vapor deposition prove the benefits of the correction procedure.

Unrevealing tunable resonant excitons and correlated plasmons and their coupling in new amorphous carbon-like for highly efficient photovoltaic devices

An understanding on roles of excitons and plasmons is important in excitonic solar cells and photovoltaic (PV) technologies. Here, we produce new amorphous carbon (a-C) like films on Indium Tin Oxide (ITO) generating PV cells with efficiency three order of magnitude higher than the existing biomass-derived a-C. The amorphous carbon films are prepared from the bioproduct of palmyra sap with a simple, environmentally friendly, and highly reproducible method. Using spectroscopic ellipsometry, we measure simultaneously complex dielectric function, loss function as well as reflectivity and reveal coexistence of many-body resonant excitons and correlated-plasmons occurring due to strong electronic correlations. X-ray absorption and photoemission spectroscopies show the nature of electron and hole in defining the energy of the excitons and plasmons as a function of N or B doping. Our result shows new a-C like films and the importance of the coupling of resonant excitons and correlated plasmons in determining efficiency of photovoltaic devices.

Bismuth zinc borate- Polyacrylonitrile nanofibers for photo-piezocatalysis

This study investigates the use of an electrospun membrane composed of Bi2ZnB2O7 - Polyacrylonitrile (BBZO-PAN) for the degradation of Methylene blue (MB) dye. The membrane was fabricated using the electrospinning technique, and its structural and morphological properties were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). The membrane's chemical states before and after encapsulation of BBZO in PAN matrix were analyzed using X-ray photoemission spectroscopy (XPS). The optical studies revealed that the band gap of the BBZO-PAN membrane was 2.92 eV, which is lower than that of the PAN membrane (4.06 eV), due to the presence of BBZO in the PAN matrix. The prepared membrane demonstrated the capability to degrade dye under visible light irradiation via photocatalysis, piezocatalysis, and photo-piezocatalysis. The highest achieved degradation and kinetic rate constant were 82% and 8.8*10-3 min−1, respectively. The active species responsible for degradation were identified using scavenger tests for all catalytic processes. These results demonstrate the potential of the BBZO-PAN membrane for use in wastewater treatment and other environmental applications.

Investigation of the magnetic and mechanical performance of fly ash Geopolymer/BaFe12O19 nanocomposites

The magnetic and mechanical properties of a geopolymer (GeO) were improved by using composites with BaFe12O19 (BFO) nanoparticles. The composites were prepared with 0, 1, 3, and 5 wt% of BFO nanoparticles. All samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometry (VSM) and compressive strength measurements. The contribution of O 1s in all samples was observed using X-Ray photoemission spectroscopy (XPS). All composite samples exhibited ferromagnetic behavior at room temperature with large hysteresis loops and increased magnetization with higher BFO nanoparticle contents. The compressive strength values of the composites increased from 58.2 to 62.2 MPa as the BFO nanoparticle content was raised from 0 to 3 wt%. An increased strength of the GeO suggests a higher denser and more compaction due to addition of BFO nanoparticles in the voids of a N-A-S-H gel structure. The LAC values for the geopolymer composites increased with BFO powder levels.

Enhanced thermoelectric properties of porous hybrid ZnSb/EG-treated PEDOT:PSS composites

We adopt a new feasible strategy to fabricate hybrid inorganic-organic composites by soaking ZnSb in EG-treated PEDOT:PSS solution. The pristine ZnSb and the hybrid ZnSb/EG-treated PEDOT:PSS composites are characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), field emission scanning electron microscope (FE-SEM), Hall measurements, electronic transport and thermal transport. The compositing effects of this hybrid material system include a decrease in lattice constants, an increase in bulk density, and a decrease in porosity with increasing soaking days. As a result, the hybrid ZnSb/EG-treated PEDOT:PSS composite with a soaking time of 30 days has a higher power factor and lower thermal conductivity than that of the pristine ZnSb. This results in an improvement in the magnitude of zT with zT = 0.71 at 525 K.

Ultra-Sensitive and Fast Humidity Sensors Based on Direct Laser-Scribed Graphene Oxide/Carbon Nanotubes Composites.

In this paper, the relative humidity sensor properties of graphene oxide (GO) and graphene oxide/multiwalled nanotubes (GO/MWNTs) composites have been investigated. Composite sensors were fabricated by direct laser scribing and characterized using UV-vis-NIR, Raman, Fourier transform infrared, and X-ray photoemission spectroscopies, electron scanning microscopy coupled with energy-dispersive X-ray analysis, and impedance spectroscopy (IS). These methods confirm the composite homogeneity and laser reduction of GO/MWNT with dominant GO characteristics, while ISresults analysis reveals the circuit model for rGO-GO-rGO structure and the effect of MWNT on the sensor properties. Although direct laser scribing of GO-based humidity sensor shows an outstanding response (|ΔZ|/|Z| up to 638,800%), a lack of stability and repeatability has been observed. GO/MWNT-based humidity sensors are more conductive than GO sensors and relatively less sensitive (|ΔZ|/|Z| = 163,000%). However, they are more stable in harsh humid conditions, repeatable, and reproducible even after several years of shelf-life. In addition, they have fast response/recovery times of 10.7 s and 9.3 s and an ultra-fast response time of 61 ms when abrupt humidification/dehumidification is applied by respiration. All carbon-based sensors' overall properties confirm the advantage of introducing the GO/MWNT hybrid and laser direct writing to produce stable structures and sensors.

Electrostatic Self-Assembly of MXene on Ruthenium Dioxide-Modified Carbon Cloth for Electrochemical Detection of Kaempferol.

A superior composite material consisting of MXene and ruthenium dioxide-modified carbon cloth is synthesized by pulsed laser deposition and electrostatic self-assembly, which is further utilized to construct a class of novel electrochemical (EC) sensors for kaempferol (KA) detection. The carbon-cloth-based electrodes modified by ruthenium dioxide and then MXene are characterized by X-ray diffraction, scanning electron microscope, and X-ray photoemission spectroscopy. The EC process on the modified electrodes is analyzed by cyclic voltammetry, EC impedance spectroscopy, and differential pulse voltammetry. It is found that positively charged RuO2 not only possesses the remarkable electrical conductivity and electrocatalysis activity but also hampers the restacking of MXene, which accordingly enhances the exposure of the active surface area and greatly boosts the electrocatalysis activity of the entire composite. Consequently, this newly developed composite-based EC sensor exhibits a high sensitivity, selectivity, and remarkable stability to detect KA with two linear ranges of 0.06-1 and 1-15 µM. The inferred limit of detection is 0.039 µM via differential pulse voltammetry. More importantly, this novel EC sensor is found to be applicable for detecting KA in practical traditional Chinese medicines.

Deep UV transparent conductive Si-doped Ga2O3 thin films grown on Al2O3 substrates

β-Ga2O3 is attracting considerable attention for applications in power electronics and deep ultraviolet (DUV) optoelectronics owing to the ultra-wide bandgap of 4.85 eV and amendable n-type conductivity. In this work, we report the achievement of Si-doped β-Ga2O3 (Si:β-Ga2O3) thin films grown on vicinal α-Al2O3 (0001) substrates with high electrical conductivity and DUV transparency of promising potential as transparent electrodes. The use of Al2O3 substrates with miscut angles promotes step-flow growth mode, leading to substantial improvement of crystalline quality and electrical properties of the Si:β-Ga2O3 films. A high conductivity of 37 S·cm−1 and average DUV transparency of 85% have been achieved for 0.5% Si-doped film grown on a 6° miscut substrate. High-resolution x-ray and ultraviolet photoemission spectroscopy were further used to elucidate the surface electronic properties of the grown Si:β-Ga2O3 films. An upward surface band bending was found at the surface region of Si:β-Ga2O3 films. Interestingly, all the Si:β-Ga2O3 films have a very low work function of approximately 3.3 eV, which makes Si:β-Ga2O3 suitable materials for efficient electron injection. The present Si:β-Ga2O3 films with high conductivity, DUV transparency, and low work function would be useful as the DUV transparent electrode to develop advanced DUV optoelectronic devices.

Impact of La3+ doping on temperature coefficient of resistivity and peak temperature of La x Ca0.89-xSr0.11MnO3 films prepared by sol-gel spin coating method

Herein, refined LaxCa0.89-xSr0.11MnO3 (LCSMO, x = 0.65, 0.68, 0.71 and 0.74) films were prepared through the sol-gel spin-coating. The influence of La3+ content on the structural properties of LCSMO films was investigated by X-ray diffraction and Atomic force microscope, demonstrating that LCSMO films can grow well on SrTiO3 (00l) substrate. Besides, X-ray photoemission spectroscopy verified the double exchange (DE) effect was weakened with La3+ dopant. The La3+ doping and interconnected grains boundaries (GBs) led to the weakening DE effect and GBs scattering, respectively. Due to superior GBs connectivity, the resistivity of LCSMO films was less than 7.1 × 10−4 Ω·cm at low temperature of 100 K. Importantly, it is an effective control method to keep the temperature (Tk) corresponding to temperature coefficient of resistivity (TCR) at room temperature with Sr2+ content as constant in LCSMO films. At x = 0.71, the peak TCR value was found to be 8.84%/K and corresponding Tk was 283.15 K. These results are beneficial for advanced application of uncooling infrared bolometer.

Silicone Oil Tamponade Removal: Which Technique Is More Effective? An X-Ray Photoemission Spectroscopy Study.

To compare the efficacy of two surgical techniques used to remove silicone oil (SiO) emulsion tamponade after pars plana vitrectomy: triple air-fluid exchange (AFX) and balanced salt solution lavage (BSSL). X-ray photoemission spectroscopy measured silicon content of the dry residue of fluid samples taken during AFX and BSSL. Ten patients underwent AFX and five BSSL. Three fluid samples were taken per patient, and the dry residue of 10 drops per sample were analyzed. A fluid sample from a patient who never received SiO tamponade was also analyzed to set a "blank" reference sample. Patients' demographics showed no significant difference. Sample 1 of the two groups contained comparable silicon content while samples 2 and 3 of the AFX group contained significantly more silicon than that of the BSSL group (15.0 ± 0.1 and 12.0 ± 0.9 for the AFX group vs. 10.7 ± 1.4 and 5.2 ± 0.6 for the BSSL group, respectively; P < 0.05). The cumulative amount of silicon in the three successive samples was also significantly higher for the AFX group (42.3 ± 1.6 vs. 32 ± 2; P < 0.0001). The average silicon content ratio of consecutive samples was significantly higher for the AFX group compared to the BSSL group (0.90 ± 0.01 vs. 0.58 ± 0.06; P = 0.006). Triple AFX removed more silicon than triple lavage. The eye wall actively interacts with silicon emulsion retaining silicon content rather than behaving as a neutral container. Triple air-fluid exchange removed more silicon than BSS lavage. Neither technique behaved as a well-mixed box dilution, suggesting the eye walls actively retain emulsion and a dynamic equilibrium is established between silicon dispersion and the eye wall surface.

Lignocellulose biomatrix zero-valent cobalt nanoparticles: a dip-catalyst for organic pollutants degradation

Pollutant removal based on natural materials got comprehensive spread utilization because of their high efficiency in degrading toxic organic pollutants in an aqueous medium. In this work, a redox dip-nanocatalyst based on cobalt nanoparticles (Co NPs) at a size of approximately 100 nm anchored on lignocellulose biomatrix via wet impregnation was used for the degradation of model pollutants. The cobalt ions immobilized on rice husk (RH) biomass fibers were reduced to their respective zero-valent state by treatment with sodium borohydride (NaBH4). The as prepared catalyst was named as RH@Co NPs. Various analytical characterization techniques viz. Fourier transforms infrared (FTIR) spectroscopy, Field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), X-Ray photoemission spectroscopy (XPS), and X-ray diffraction analysis (XRD) were used to examine functional group analysis, morphological characteristics, stability, elemental composition, and crystalline nature of the as-prepared RH@Co nanocatalyst respectively. The catalytic properties of the RH@Co NPs were tested using different nitrophenols viz. 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), 4-nitrophenol (4-NP), and dyes viz. congo red (CR), methyl orange (MO), methylene blue (MB), and rhodamine B (RB). It was found that kinetic data followed zeroth order kinetics for the degradation of model pollutants. The RH@Co showed good catalytic activity for 2-NP, 3-NP, and 4-NP with apparent rate constants (kapp) of 0.019 min−1, 0.029 min−1, and 0.0416 min−1, respectively. Similarly, in the case of CR, MO, RB, and MB dyes, the kapp was 0.067 min−1, 0.12 min−1, 0.16 min−1, and 0.085 min−1, respectively. These results present the potential application of RH@Co as a sustainable and retrievable nanocatalyst for the remediation of pollutants. Furthermore, the results are general and can be used for the reduction of other organic pollutants.

X-ray irradiation-induced ligand cleavage of a phthalocyanine derivative, tin (IV) phthalocyanine dichloride: A potential for X-ray activation of caged compounds

The X-ray dissociation of tin (IV) phthalocyanine dichloride (SnCl2Pc) was investigated using X-ray photoemission spectroscopy. The photoemission spectra of SnCl2Pc after X-ray irradiation exhibited additional components assigned as chloride ions and tin (II) phthalocyanine, as well as decomposition products from the phthalocyanine framework, indicating that X-ray irradiation induced the release of chloride ions as ligands from SnCl2Pc. Although the ligand releases were caused not by a simple cleavage between Cl-Sn bonding but by accompanying the molecular framework destruction, these reactions may robustly facilitate a novel application of X-rays to activate caged compounds in tissues.

Solid‐State Synthesis and Characterization of Mg‐Substituted P2‐Na0.70Ni0.45Mn0.55O2 Cathode Materials for Practical Sodium‐Ion Batteries

AbstractSodium ion batteries are considered as a potential alternative to existing Li‐ion batteries. Layered transition metal oxides are found to be suitable cathode candidates for Na‐ion batteries. In this study, solid state synthesis of P2‐Na0.7Ni0.45Mn0.55O2 with different Mg substitutions is reported. The synthesized materials are characterized thoroughly using X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FE‐SEM), energy dispersive spectroscopy (EDS), inductively coupled plasma atomic emission spectroscopy (ICP‐AES), and x‐ray photoemission spectroscopy (XPS) analysis. SEM analysis reveals the morphology of synthesized materials to layered structure with a particle size in the range of 5–50 µm. Powder XRD shows all synthesized materials of P2 structure irrespective of Mg substitution. A spurious P3 phase is observed in 0% and 5% of Mg substituted samples which are absent in 10% and 15% of Mg substituted materials. Electrochemical performance analysis shows specific capacity reduces with Mg substitution whereas mid‐voltage reaches maximum up to 3.5 V with 10% substitution. 10% Mg substituted NMO shows a specific capacity 105 mA h g−1 in the voltage ranges of 2–4.3 V versus Na/Na+ with excellent cycling stability and rate capability.

Intrinsic resistive switching in ultrathin SiOx memristors for neuromorphic inference accelerators

Two-dimensional (2D) materials are promising memristive materials owing to their outstanding physical properties, electrical tunability and fast switching capability. However, 2D layered materials generally require sophisticated deposition techniques at the expense of limited large-scale homogeneity and high growth temperatures. Furthermore, the variability and reliability of the 2D materials based memristor should be further improved. Here, we report an intrinsic memristor based on ultrathin 2D-like nonlayered amorphous SiOx which is derived from a native oxidation process at ambient temperature. Such 2D-like memristors demonstrate low switching variability (3.7 %), nanosecond switching speed (15 ns), good endurance (>106 cycles) and high retention (>103 s at 85 °C). We verified the resistive switching mechanism via in-depth X-ray photoemission spectroscopy (XPS) analysis at different resistance states and confirmed the oxygen vacancies movement under the electric field between the SnOx reservoir layer and the SiOx layer. Moreover, Simulation results for an MNIST image classifier based on the ultrathin SiOx memristor show a high recognition accuracy of ∼ 98 %, manifesting its potential for the practical implementation of nonlayered 2D-like materials based neural network inference accelerator.

A New Approach in Prebiotic Chemistry Studies: Proline Sorption Triggered by Mineral Surfaces Analysed Using XPS.

The role of minerals in the origin of life and prebiotic evolution remains unknown and controversial. Mineral surfaces have the potential to facilitate prebiotic polymerization due to their ability to adsorb and concentrate biomolecules that subsequently can catalyse reactions; however, the precise nature of the interaction between the mineral host and the guest biomolecule still needs to be understood. In this context, we spectroscopically characterized, using infrared, X-ray photoemission spectroscopy (XPS) and X-ray diffraction (XRD) techniques, the interaction between L-proline and montmorillonite, olivine, iron disulphide, and haematite (minerals of prebiotic interest), by evaluating their interaction from a liquid medium. This work provides insight into the chemical processes occurring between proline, the only cyclic amino acid, and this selection of minerals, each of them bearing a particular chemical and crystal structures. Proline was successfully adsorbed on montmorillonite, haematite, olivine, and iron disulphide in anionic and zwitterionic chemical forms, being the predominant form directly related to the mineral structure and composition. Silicates (montmorillonite) dominate adsorption, whereas iron oxides (haematite) show the lowest molecular affinity. This approach will help to understand structure-affinity relationship between the mineral surfaces and proline, one of the nine amino acids generated in the Miller-Urey experiment.