Uncharged Surface Research Articles

An Analytical Adhesion Model for Elastic Contact Electrification

Abstract Contact electrification is a universal phenomenon that commonly occurs in almost every solid–solid contact pair. The tribo-charges deposited on two surfaces by contact electrification can significantly affect adhesion; however, contact electrification is often overlooked in the study of adhesive contact. Here, we develop an analytical model to investigate electroadhesion during the contact phase between two initially uncharged dielectric surfaces, namely, an elastic parabolic surface and a rigid flat. A system of nonlinear equations is derived to describe the relationship between the indentation, normal load, radius of contact area, and radius of the charged zone using the Barthel–Maugis–Dugdale model (Barthel, 1999, “Modelling the Adhesion of Spheres: When the Form of the Interaction Is Complex, Colloids. Surf., A., 149, pp. 99105.). The analytical results show good agreement with the numerical results of the full self-consistent contact model. When contact electrification leads to a higher tribo-charge density and a larger charged zone, it has a greater impact on the normal traction, interfacial gap, force-approach curves, jump-out, and dissipated energy. The analytical model developed in this study serves as the foundation for advances in rough surface electroadhesive contact and electroadhesion testing, and it sheds light on the usage of adhesive joints in ultra-high vacuum environments and outer space, where contact electrification has a significant impact.

Adsorption behaviors and mechanisms of bilirubin onto charged amorphous carbon surface with and without water by a molecular dynamics simulation

The adsorption of bilirubin onto a carbon surface holds pivotal significance in enhancing bilirubin clearance efficiency within artificial liver devices. We performed molecular dynamics simulations to reveal the adsorption behaviors and mechanisms of bilirubin onto a charged amorphous carbon surface. The hydrogen atoms are used as binding sites facilitating the adsorption of bilirubin molecules onto the uncharged amorphous carbon surface. Conversely, the oxygen atoms are used as binding sites, enhancing bilirubin adsorption on charged amorphous carbon surfaces due to their higher electronegativity. The bilirubin adsorption rate, the mean-squared displacements of bilirubin, and the interaction energy between bilirubin and amorphous carbon increase as the surface charge increases, and the adsorption amount reaches an asymptotic value as the surface charge approaches a certain threshold. In the presence of water, the competitive adsorption between bilirubin and water would occur. The hydration layer formed on charged amorphous carbon surface and the electrostatic and near-wall hydrogen-bond interactions emerge as two pivotal factors influencing bilirubin adsorption. The structured arrangement of hydration water can hinder the bilirubin adsorption, whereas the electrostatic interaction and near-wall hydrogen-bond interaction promote it. The whole competitive adsorption process unfolded in distinct stages of bilirubin adsorption and desorption, and a critical value of surface charge exists for the complete desorption of bilirubin.

Ternary Solid Polymer Electrolytes at the Electrochemical Interface: A Computational Study.

Polymer-based solid-like gel electrolytes have emerged as a promising alternative to improve battery performance. However, there is a scarcity of studies on the behavior of these media at the electrochemical interface. In this work, we report classical MD simulations of ternary polymer electrolytes composed of poly(ethylene oxide), a lithium salt [lithium bis(trifluoromethanesulfonyl)imide], and different ionic liquids [1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide] confined between two charged and uncharged graphene-like surfaces. The molecular solvation of Li+ ions and their diffusion as well as the polymer conformational picture were characterized in terms of the radial distribution functions, coordination numbers, number density profiles, orientations, displacement variance, polymer radius of gyration, and polymer end-to-end distance. Our results show that the layering behavior of the ternary electrolyte in the interfacial region leads to a decrease of Li+ mobility in the direction perpendicular to the electrodes and high energy barriers that hinder lithium cations from coming into direct contact with the graphene-like surface. The nature of the ionic liquid and its concentration were found to influence the structural and dynamic properties at the electrode/electrolyte interface, the electrolyte with low amounts of the pyrrolidinium-based ionic liquid being that with the best performance since it favors the migration of Li+ cations toward the negative electrode when compared to the imidazolium-based one.

Electret‐induced antibacterial response of Mg1‐xCaxSi1‐xZrxO3 (x = 0–0.4) bioceramics

AbstractThe potential risk of bacteria‐induced prosthetic infection during implantation/post‐operative healing raises a serious concern about the success of implant/surgery. In this context, the present study successfully established the antibacterial efficacy of the electret form of Mg1‐xCaxSi1‐xZrxO3 (x = 0, 0.1, 0.2, 0.3, 0.4 [MCSZO‐X]) bioceramics, toward both, Escherichia Coli and Staphylococcus aureus bacteria with reference to those of hydroxyapatite (HAP). MCSZO‐X bioceramics were synthesized using a solid‐state route. The influence of Ca‐ and Zr co‐doping on the crystallite size of MCSZO‐X has been analyzed using X‐ray peak profile analyses. The electrets were developed by corona poling of sintered MCSZO‐X samples at voltage and temperature of 20 kV and 500°C (30 min), respectively. The charge, stored on the surface of MCSZO‐X electret samples was calculated to be 0.253, 0.294, 0.320, 0.173, and 0.161 µC/cm2 via thermally stimulated depolarized current measurement. The positive and negative ends of MCSZO‐ X electrets exhibited a reduction in the viability of E. coli bacteria by (24%, 25%, 30%, 43%, and 42%) and (29%, 37%, 39%, 51%, and 48%), respectively, in comparison to those of HAP. On the contrary, the viability of S. aureus bacteria has decreased by (26%, 33%, 35%, 46%, and 42%) and (21%, 22%, 27%, 395, and 37%) on the surfaces of the positive and negative ends of MCSZO‐ X electrets, respectively, with the reference of those of HAP. The mechanism of electret‐induced antibacterial activity has been revealed via various assays, such as catalase activity, superoxide production (SOD), , protein estimation, and lipid peroxidation (LPO) assays. The positive ends of MCSZO‐X electrets demonstrate antibacterial efficacy by means of more reactive oxygen species generation as compared to their negative ends of electrets and uncharged surfaces of MCSZO‐X samples, as revealed by SOD, protein estimation, catalase activity, and LPO assays. However, the negative ends of electrets prevent the adhesion of bacterial cells via electrostatic repulsion.

Tangential Casimir force in the misaligned system: Magnetic media, real conductors, and a torque

Uncharged parallel plates in the misaligned system can experience a tangential Casimir force between them. We consider the role of magnetic response in this effect by extending the tangential force to magnetic media, and the extension is realized by working out the total zero-point energy of multilayered magnetodielectrics. Then we investigate the tangential force for real conductors by taking into account the temperature dependence of their dielectric constants, and obtain needed results for experimental investigations that are expected to be conducted at room temperature. Thereafter, we discuss a Casimir torque between parallel plates made of isotropic media, which offers a simple way to realize torques for uncharged surfaces.

Relationships between Water's Structure and Solute Affinity at Polypeptoid Brush Surfaces.

Excellent antifouling surfaces are generally thought to create a tightly bound layer of water that resists solute adsorption, and highly hydrophilic surfaces such as those with zwitterionic functionalities are of significant current interest as antifoulant strategies. However, despite significant proofs-of-concept, we still lack a fundamental understanding of how the nanoscopic structure of this hydration layer translates to reduced fouling, how surface chemistry can be tuned to achieve antifouling through hydration water, and why, in particular, zwitterionic surfaces seem so promising. Here, we use molecular dynamics simulations and free energy calculations to investigate the molecular relationships among surface chemistry, hydration water structure, and surface-solute affinity across a variety of surface-decorated chemistries. Specifically, we consider polypeptoid-decorated surfaces that display well-known experimental antifouling capabilities and that can be synthesized sequence specifically, with precise backbone positioning of, e.g., charged groups. Through simulations, we calculate the affinities of a range of small solutes to polypeptoid brush surfaces of varied side-chain chemistries. We then demonstrate that measures of the structure of surface hydration water in response to a particular surface chemistry signal solute-surface affinity; specifically, we find that zwitterionic chemistries produce solute-surface repulsion through highly coordinated hydration water while suppressing tetrahedral structuring around the solute, in contrast to uncharged surfaces that show solute-surface affinity. Based on the relationship of this structural perturbation to the affinity of small-molecule solutes, we propose a molecular mechanism by which zwitterionic surface chemistries enhance solute repulsion, with broader implications for the design of antifouling surfaces.

Superfast adsorption of small and uncharged urea from water using post-sonicated iron-based metal-organic framework

Urea is widely used in fertilizer production for agricultural purposes which risks runoff into soil and water sources. An excess of urea can result in algal or toxic blooms which can poison wildlife or even humans by accumulation in food sources. The removal of urea from water is challenging due to the small size (0.254 nm) and uncharged surface of urea. Intensive research has been conducted on a variety of methods to remove environmental concentrations of urea using adsorbents, but most of them lack effective removal, require long (>2 h) process time, and lack re-generability. Metal-organic frameworks (MOFs) are the new generation of adsorbents with excellent structural and functional group tunability. In this study, we synthesized MIL-100 (Fe), an iron-based MOF, as an efficient adsorbent for the removal of uncharged urea from water. The urea adsorption capacity of MIL-100 (Fe) was tested under varying experimental conditions such as pH (2–10), temperature (25–65 °C), MOF concentration (25–400 ppm), and urea concentration (25–1000 ppm). The results showed the superfast adsorption (more than 85% removal within 2 min) of neutrally charged urea molecules on MIL-100 (Fe). The MOF was able to reach a maximum adsorption efficiency of around 85% with a maximum uptake capacity of 3321 mg/g. The MIL-100 (Fe) showed acceptable re-generability by retaining up to 90% removal efficiency after four regeneration cycles. The urea adsorption followed pseudo 2nd-order adsorption kinetics and dipole-dipole interactions and π-NH bonding were the primary adsorption mechanism.

Medical imaging applied to heritage.

The use of imaging has transformed the study of cultural heritage artefacts in the same way that medical imaging has transformed medicine. X-ray-based techniques are common in both medical and heritage imaging. Optical imaging, including scientific photography and spectral imaging techniques, is also common in both domains. Some common medical imaging methods such as ultrasound and MRI have not yet found routine application in heritage, whereas other methods such as imaging with charged and uncharged particles and 3D surface imaging are more common in heritage. Here, we review the field of heritage imaging from the point of view of medical imaging and include some classic challenges of heritage imaging such as reading the text on burnt scrolls, identifying underdrawings in paintings, and CT scanning of mummies, an ancient calculating device and sealed documents. We show how hyperspectral imaging can offer insight into the drawing techniques of Leonardo da Vinci and explain how laparoscopy has identified the method of construction of a 500-year-old pop-up anatomical text book.

Eco-friendly aqueous foam stabilized by cellulose microfibers with great salt tolerance and high temperature resistance

A low-cost eco-friendly aqueous foam, especially the robust foam with great tolerance to high salinity and high temperature, is in great demand in the oil industry, e.g., oil and gas well or geothermal well drilling. Herein, an ultra-stable aqueous foam was developed using the biodegradable cellulose microfiber (CMF) as a foam stabilizer. The foam stabilized by CMF shows excellent tolerance to the high concentration of NaCl (6.0 wt%) and CaCl2 (0.25 wt%) and the related drainage half-life times (T0.5) reach 1750 and 2340 s respectively. By contrast, the foams without CMF are completely drained (T0.5 = 0 s) when NaCl concentration is greater than 6.0 wt% or CaCl2 concentration is greater than 0.20 wt%. Notably, T0.5 of the foams stabilized by CMF at these saline concentrations still can maintain above 1000 s even after aging at 120 °C for 16 h, exhibiting an outstanding foam-stabilizing performance at high temperature. Experimental results suggest that the salt and high-temperature tolerance of CMF in foam stabilization is attributed to the electrically uncharged surfaces, the formation of a gel-like structure and the excellent thermal stability. This work not only provides a promising candidate of aqueous foam stabilizer to deal with high temperature and high salinity but also presents a natural-based solution for an environmentally friendly drilling industry in the future.

Protonation of Surface Carboxyls on Rice Straw Cellulose Nanofibrils: Effect on the Aerogel Structure, Modulus, Strength, and Wet Resiliency.

Rice straw cellulose nanofibrils from the optimal 2,2,6,6-tetramethylpiperidine-1-oxyl oxidation/blending process carrying 1.17 mmol/g surface carboxyls were protonated to varying charged (COO-Na+) and uncharged (COOH) surfaces. Reducing the electrostatic repulsion of surface charges by protonation with hydrochloric acid from 11 to 45 and 100% surface carboxylic acid most prominently reduced the aerogel densities from 8.0 to 6.6 and 5.2 mg/cm3 while increasing the mostly open cell pore volumes from 125 to 152 and 196 mL/g. Irrespective of charge levels, all aerogels were amphiphilic, super-absorptive, stable at pH 2 for up to 30 days, and resilient for up to 10 repetitive squeezing-absorption cycles. While these aerogels exhibited density-dependent dry [11.3 to 1.5 kPa/(mg/cm3)] and reduced wet [3.3 to 1.4 kPa/(mg/cm3)] moduli, the absorption of organic liquids stiffened the saturated aerogels. These data support protonation as a critical yet simple approach toward precise control of aerogels' dry and wet properties.

On the contact conditions for the density and charge profiles in the theory of electrical double layer: From planar to spherical and cylindrical geometry

In this paper, starting from the Bogoliubov-Born–Green–Yvon equations of the liquid-state theory, we formulate two equivalent approaches for the calculation of the total density profile and of the charge density profile of ionic fluids near nonplanar charged surfaces. In the framework of these approaches, we establish exact conditions, that a particular point of these profiles should satisfy, in the form of contact theorems. These contact theorems for the total density profile and the charge density profile are obtained by direct integration of a system of equations derived from the Bogoliubov-Born–Green–Yvon equations. The contact theorems for both profiles have nonlocal character. It is shown that the contact value of the total density profile for uncharged surfaces is characterized by the bulk pressure and the surface tension. The contact theorems are applied to the cases of spherical and cylindrical surfaces. It is shown that the contact theorem for the total density profile coincides with the recent results obtained by W. Silvester-Alcantara, D. Henderson and L.B. Bhuiyan (Mol. Phys., 113, 3403, 2015).

Ionic liquids on uncharged and charged surfaces: In situ microstructures and nanofriction

In situ changes in the nanofriction and microstructures of ionic liquids (ILs) on uncharged and charged surfaces have been investigated using colloid probe atomic force microscopy (AFM) and molecular dynamic (MD) simulations. Two representative ILs, [BMIM][BF4] (BB) and [BMIM][PF6] (BP), containing a common cation, were selected for this study. The torsional resonance frequency was captured simultaneously when the nanoscale friction force was measured at a specified normal load; and it was regarded as a measure of the contact stiffness, reflecting in situ changes in the IL microstructures. A higher nanoscale friction force was observed on uncharged mica and highly oriented pyrolytic graphite (HOPG) surfaces when the normal load increased; additionally, a higher torsional resonance frequency was detected, revealing a higher contact stiffness and a more ordered IL layer. The nanofriction of ILs increased at charged HOPG surfaces as the bias voltage varied from 0 to 8 V or from 0 to —8 V. The simultaneously recorded torsional resonance frequency in the ILs increased with the positive or negative bias voltage, implying a stiffer IL layer and possibly more ordered ILs under these conditions. MD simulation reveals that the [BMIM]+ imidazolium ring lies parallel to the uncharged surfaces preferentially, resulting in a compact and ordered IL layer. This parallel “sleeping” structure is more pronounced with the surface charging of either sign, indicating more ordered ILs, thereby substantiating the AFM-detected stiffer IL layering on the charged surfaces. Our in situ observations of the changes in nanofriction and microstructures near the uncharged and charged surfaces may facilitate the development of IL-based applications, such as lubrication and electrochemical energy storage devices, including supercapacitors and batteries.

Water contact angles on charged surfaces in aerosols

Interactions between water and solid substrates are of fundamental importance to various processes in nature and industry. Electric control is widely used to modify interfacial water, where the influence of surface charges is inevitable. Here we obtain positively and negatively charged surfaces using LiTaO3 crystals and observe that a large net surface charge up to 0.1 C/m2 can nominally change the contact angles of pure water droplets comparing to the same uncharged surface. However, even a small amount of surface charge can efficiently increase the water contact angle in the presence of aerosols. Our results indicate that such surface charges can hardly affect the structure of interfacial water molecular layers and the morphology of the macroscopic droplet, while adsorption of a small amount of organic contaminants from aerosols with the help of Coulomb attraction can notably decrease the wettability of solid surface. Our results not only provide a fundamental understanding of the interactions between charged surfaces and water, but also help to develop new techniques on electric control of wettability and microfluidics in real aerosol environments.

Effects of Methyl, Ester, and Amine Surface Groups on Microbial Activity and Communities in Nitrifying Biofilms.

The objective of this study was to determine how different attachment surface chemistries affected the initial and long-term performance and microbial populations of nitrifying biofilms under well-controlled hydrodynamic mixing conditions. While much previous research has focused on the effects of surface properties such as hydrophobicity on bacterial attachment in pure cultures, this study evaluated the effects of specific functional groups on mixed culture composition and functional behavior. Three surfaces with varying hydrophobicity and charge were evaluated for biofilm community development and performance: unmodified poly(dimethylsiloxane) (PDMS), which included terminal methyl groups and was relatively hydrophobic (P-Methyl), PDMS silanized with ester groups (P-Ester), which was uncharged and relatively hydrophilic, and PDMS modified with amine groups (P-Amine), which possessed a positive charge and was the most hydrophilic. The surface chemistries of the three attachment surfaces were characterized by contact angle goniometry, Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). These surfaces were inoculated with dilute activated sludge, and biofilms were grown in rotating annular bioreactors for 80 days, with experimental triplicates. Nitrification rates increased most rapidly in P-Amine biofilm reactors, and their biofilm communities contained significantly more Nitrosomonas (p < 0.05) than those on the other surfaces in early growth stages (days 40-50). From days 50-60, the P-Amine surface biofilm had significantly higher nitrate production rates than the P-Methyl and P-Ester biofilms. The biofilms grown on the P-Amine and P-Methyl surfaces were significantly (p < 0.05) more diverse than the P-Ester biofilms, containing higher relative abundances of the order Rhizobiales, including a significantly higher abundance of the nitrifying genus Nitrobacter (p < 0.05), which coincided with higher rates of nitrate generation. Conversely, biofilms grown on the uncharged hydrophilic P-Ester surface were consistently less productive and had lower diversity than biofilms on the other surfaces. These results indicate that surface chemistry may be a useful design parameter to improve the performance of nitrifying biofilm systems for wastewater treatment and that surface chemistry affects mixed biofilm community composition.

Asymmetric boundary conditions and their relevance in minimal passive mass species transport in time-periodic electro-osmotic flows

A set of dimensionless groups along with constraints on their values are formulated to serve as an indication of the parametric combinations, leading to minimal enhancement of streamwise passive species transport in time-periodic electro-osmotic microchannel flows with asymmetric hydrodynamic slip and zeta potential boundaries. While the slip lengths and zeta potentials are mostly treated as uncoupled in the electrokinetic transport literature, we incorporate into the analysis wall surface charge/potential coupled apparent slip lengths and find that more than one minimal enhancement instances may be achieved during a zeta potential sweep, provided that the uncharged surface slip length ratio is large enough.

The Lubricating Activity of Phospholipids on Charged and Neutral Surfaces

Abstract In this paper, the amphoteric character of cartilage surface is used to study friction between charged (+/+), (−/−), and uncharged (±/±) biological surfaces. The surface of the bovine articular cartilage at varying pH solutions is either charged positively or negatively. When examining the coefficient of friction of the (cartilage/cartilage) pair, depending on the pH, we observe surfaces charged positively, negatively, and without charge. The uncharged surface refers to the iso-electric point (IEP) and shows greater friction than the charged surfaces of the cartilage. The measurement of surface energy versus. pH of the spherical lipid bi-layer will reveal the amphoteric nature of the membrane surface. The friction coefficient of the (cartilage/cartilage) pair and the surface energy of the spherical lipid bi-layer versus pH are expressed by a bell-shaped curve. This is an interesting case that confirms the fact that the phospholipid bi-layer is embedded on the surface cartilage. This experimental confirmation of negative surface cartilage is insufficiently highlighted in the literature on natural lubrication.

Interfacial interactions between protective, surface-engineered shells and encapsulated bacteria with different cell surface composition.

Surface-engineered encapsulation is a non-genetic method to protect living organisms against harsh environmental conditions. Different cell encapsulation methods exist, yielding shells with different interfacial-interactions with encapsulated, bacterial surfaces. However, the impact of interfacial-interactions on the protection offered by different shells is unclear and can vary for bacteria with different surface composition. Probiotic bacteria require protection against gastro-intestinal fluids and antibiotics. Here, we encapsulated two probiotic strains using ZIF-8 (zeolitic imidazolate framework) biomineralization (strong-interaction by coordinate-covalent bonding), alginate gelation (intermediate-interaction by hydrogen bonding) or protamine-assisted packing of SiO2 nanoparticles yielding a yolk-shell (weak-interaction across a void between shells and bacterial surfaces). The surface of probiotic Lactobacillus acidophilus was rich in protein, yielding a hydrophilic, positively-charged surface below and a negatively-charged one above pH 4.0. Probiotic Bifidobacterium infantis had a hydrophilic, uncharged surface, rich in polysaccharides with little proteins. Although amino groups are required for coordinate-covalent bonding of zinc and hydrogen bonding of alginate, both L. acidophilus and B. infantis could be encapsulated using ZIF-8 biomineralization and alginate gelation. Weakly, intermediately and strongly interacting shells all yielded porous shells. The strongly interacting ZIF-8 biomineralized shell made encapsulated bacteria more susceptible to antibiotics, presumably due to the cell wall damage already inflicted during Zif-8 biomineralization. Overall, weakly interacting yolk-shells and intermediately interacting alginate gels protected best and maintained probiotic activity of encapsulated bacteria. The impact of interfacial-interactions between shells and encapsulated bacteria on different aspect of protection described here, contributes to the further development of effective surface-engineered shells and its application for protecting bacteria.

Enhanced degradation of ofloxacin by persulfate activation with Mn doped CuO: Synergetic effect between adsorption and non-radical activation

Non-radical activation of persulfate (PS) is a promising technology for removing organic pollutants in water because of the higher selectivity and stability of activated PS than radicals. Hence, the development of effective catalyst for PS non-radical activation is highly desired. In this work, a series of Mn doped CuO samples were prepared and used for removing ofloxacin with PS activation. The correlation between their surface properties and catalytic performance was studied, and the key parameter affecting pollutant degradation was explored. The result indicates that the CM3 sample (Cu:Mn = 6:1) exhibited the highest activity for ofloxacin degradation at neutral pH due to its high adsorption capacity towards ofloxacin and high activity for non-radical activation of PS, which is beneficial for their surface reaction. The large surface area and uncharged surface of CM3 at neutral pH facilitate the adsorption of ofloxacin, while its surface Cu2+ with less electron deficiency might be responsible for the production of activated PS. Because ofloxacin was mainly degraded by the activated PS, the common ions in real water had little effect on this process. The toxicity assessment indicates that the treated ofloxacin solution was harmless. Finally, the reusability experiment demonstrates that CM3 is a stable and effective catalyst for non-radical activation of PS.

Biochar as agricultural alternative to protect the rice plant growth in fragile sandy soil contaminated with cadmium

Abstract Contamination by cadmium (Cd) is a serious problem in fragile sandy soils. In these soils, the high amount of sand fractions with uncharged surface and low organic matter content cause the high mobility of Cd. Biochar has been shown to be highly promising for mitigating adverse effects on soils, but little is known about its role in Cd-contaminated fragile soils. The aim of this study was to obtain biochar from different biomasses and evaluate their effects on root growth in rice plants and their protective effects against Cd stress in a Planosol. Three biochar obtained were characterized by 13C NMR and elemental composition. In the first experiment, biochar was added to the Planosol at different ratios (1.0%, 2.0%, and 3.0%), and root growth and photosynthesis parameters were evaluated after 28 days of growth. In the second experiment, the plants were grown in a Planosol with biochar (3.0%) contaminated with Cd, and the plant antioxidative defense parameters were evaluated. Biochar at 3.0% stimulated the growth of plant roots, as well as the photosynthetic pigment contents. The biochar showed a protective effect on the rice plants, decreasing the reactive oxygen species and malondialdehyde content and increasing the membrane permeability preservation when plants were subjected to Cd stress. Biochar may be an ecologically sustainable material for the preservation of soils and plants under conditions of fragile soils.

Photoelectron distribution on sunlit surface of the Moon: A formalism

An analytical formulation describing the characteristic energy distribution of photoelectrons over the sunlit regolith of the Moon has been presented. In deriving the distribution function, Fowler's approach based on fermionic lattice electrons for photoemission has been coupled with observed solar spectra, photoelectric quantum yield, and latitude dependent surface temperature. It is noticed that the dominant contribution in the photoelectron distribution function comes from extreme ultraviolet photons (3 eV–300 eV) of the solar spectra. The analysis also illustrates that the photoelectron distribution for the observed solar spectra is significantly different from the spectrum based on Planck's radiation law. In results, the photoelectron distribution is found to be a significant function of the lunar surface potential—the photoelectron distribution in the steady state considerably differs from that of the uncharged surface. In calculations, the variation in the photoelectron distribution function with the lunar latitude, quantum yield, and work function of the surface material has been parametrically analyzed, and it is found to be sensitive to the constituent parameters.