Nylon- and cotton-based fabrics, particularly a 50:50 nylon-cotton blend ("NYCO"), are commonly used for military and workforce garments. Developing high-throughput methods to attach reactive or sorptive metal oxide or metal-organic framework (MOF) nanoparticles (NPs) is important for chemical protection. Open-air plasma treatment has been used to activate cotton, nylon, and NYCO such that they covalently bond to ca. 20 nm zinc oxide and UiO-66-NH2 MOF particles. For cotton, X-ray photoelectron spectroscopy (XPS) shows that plasma treatment partially oxidizes cellulose, with transformation of aliphatic carbons to hydroxyl and carbonyl groups. For nylon, XPS indicates the formation of additional hydroxyl groups and transformation of some amide groups to hydroxyamides. Plasma-treated fabrics and untreated controls were spray-coated with ethanolic suspensions of ZnO or UiO-66-NH2 particles, ultrasonicated in ethanol, and air-dried. In some cases, particle-covered fabrics were machine-washed to assess durability. For all three fabrics, scanning electron microscopy (SEM) and XPS demonstrated that plasma treatment significantly enhances the surface concentration of ZnO NPs that remain after ultrasonication. However, machine washing removes most of the ZnO NPs, with minimal differences between untreated and plasma-treated fabrics. In the case of UiO-66-NH2, particle sizes of ca. 200 and 500 nm were evaluated, and adhesion was significantly better on NYCO for the smaller particles due to more attachment sites per unit mass; a significant surface concentration of the smaller MOF remains on NYCO even after five wash cycles. To demonstrate the efficacy of the process for treating fabrics to impart chemical protection, permeation times of the nerve agent simulant dimethyl methylphosphonate were compared for bare and MOF-functionalized NYCO. The functionalized fabric exhibited a permeation time that was almost three times greater than for bare, plasma-treated fabric. These results demonstrate the practicality of the process for high-throughput preparation of metal oxide and UiO-66-NH2 functionalized NYCO for chemical protection.

Methods to attach metal oxide nanoparticles (MONPs) to inert supports such as polymers, fabrics and membranes, are important for applications that include filtration, lithium-ion battery separators, and photocatalysis. In the present study, a high-throughput method that consists of open-air plasma treatment of polypropylene (PP) knitted fabric, followed by spray-coating with ethanolic colloidal suspensions of various MONPs, has been investigated. X-ray photoelectron spectroscopy (XPS) indicates that open-air plasma treatment forms surface hydroxyl, carbonyl and carboxylic acid groups. The water contact angle of similarly treated spin-coated PP films decreases to 80 degrees, compared to 97 degrees for untreated PP. XPS and field emission scanning electron microscopy (FE-SEM) of plasma-treated and untreated controls spray-coated with MONPs, rinsed, and ultrasonicated in ethanol show that plasma treatment leads to enhanced particle adhesion. MONPs that act as weak Lewis acids, such as ZnO, MgO and In2O3, essentially completely coat the fibers, while more acidic MONPS, such as CeO2, SiOx, SnO2, TiO2, and WO3, adhere relatively poorly, even on plasma-treated fabric. Metal oxide coverage, determined by XPS, inversely correlates with the polarizing power of the cation in the metal oxide. It is hypothesized that the metal oxide hydroxyl groups play a key role in adhesion, with strong Lewis acid MONPs exhibiting weaker hydrogen bonding to the polar functional groups (e.g., carbonyl groups) of the plasma-treated PP. Photocatalytic application of this method of attaching nanoparticles is demonstrated by ultraviolet light-induced decomposition of methyl paraoxon by ZnO-functionalized PP.

Protective fabrics that combine chem-bio (CB) protection, flame retardancy, and thermal comfort are critical for high-risk applications. However, achieving this combination for lightweight and breathable materials remains a significant challenge. This study reports the development of a breathable multifunctional nylon/cotton blend (50:50) (Nyco) fabric with an electrospun thermoplastic polyurethane (TPU) membrane for enhanced chem-bio protection and flame retardancy. The composite membrane was fabricated by electrospinning a TPU solution containing a zirconium-based metal-organic framework (MOF) along with tannic acid, a nonhalogenated flame retardant onto a phosphoric acid-treated Nyco fabric. The samples were investigated by analyzing their morphology, thermal stability, chemical resistance, flammability, air permeability, and particle filtration efficiency. Morphological analysis showed electrospun nanofibers (0.2-0.4 mu m diameter) with well-dispersed MOF particles of about 0.5-5 mu m. Thermal analysis demonstrated reduced degradation temperatures with enhanced char formation (up to 29.53%), providing an effective thermal barrier necessary for enhanced thermal stability. Flammability tests confirmed improved flame resistance of the composite membranes, showing shorter char lengths (6 in.) and reduced after-flame times (5 s), compared to untreated samples. Cone calorimetry further demonstrated enhanced fire performance with the optimized composite reducing the peak heat release rate and total heat release by up to 23% and 24%, respectively. Chemical resistance testing using the nerve agent simulant dimethyl methyl phosphonate (DMMP) demonstrated the fabric's superior chemical protective capabilities. The integration of MOFs resulted in extended breakthrough times (5.2 min, 10-fold) due to the presence of the electrospun membrane layer and MOFs' high surface area and reactivity contributing to the effective adsorption of DMMP. These results demonstrate a clear and systematic improvement in chemical resistance relative to untreated control Nyco. The air permeability (4.07 L m-2 s-1) and particle filtration efficiency (99.99%) tests revealed an optimized balance between breathability and protective performance, ensuring protection without compromising comfort. The results highlight the potential of these advanced materials for protective clothing applications in high-risk environments, offering a unique combination of lightweight design, durability, and multifunctionality, making them promising candidates for military, emergency response, and industrial safety applications.

The reaction of l-cysteine and cysteamine hydrochloride with zinc oxide nanoparticles (ZnO NPs), by stirring excess reactant with the NPs in ethanol, has been studied by thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. l-Cysteine adsorption occurs via the thiol functional group, and there is no evidence for bonding via the carboxylic acid or amine functionalities. However, Raman spectroscopy and XPS reveal some protonated thiol, suggesting unbound l-cysteine is also present, as confirmed by XRD that shows the presence of l-cysteine crystallites. In the case of cysteamine/ZnO, TGA indicates that a large fraction of the sample is organic, and Raman spectroscopy reveals a dramatic shift in the C-S stretch from 796 cm-1 for unreacted cysteamine to 837 cm-1 for the reacted cysteamine. It is postulated that the acidic and chelating nature of the reaction causes dissolution of some Zn2+ ions that form a Zn(II) coordination complex with cysteamine. These studies have implications for biomolecular applications in which ZnO nanoparticles are used for biosensors, bioimaging, and drug delivery.

Despite numerous tutorials and standards written to the technical community on X-ray photoelectron spectroscopy (XPS), difficulties with data acquisition, analysis, and reporting persist. This work focuses on common errors in XPS that are frequently observed in the scientific literature and their sources. Indeed, this work covers: (i) XPS data collection, initial data analysis, and data presentation, (ii) Handling XPS backgrounds, (iii) Common errors in XPS peak fitting, and (iv) XPS data presentation and reporting. Graphical examples of errors and appropriate ways of handling data and correcting errors are provided. Additional readings are listed for greater in-depth exploration of the subjects discussed.

Ultraviolet photoelectron spectroscopy (UPS) is an important technique for measuring the energies of the valence states of metallic, semiconducting and adsorbate-covered metal and semiconducting surfaces. Applications include catalysis, organic electronics, optoelectronic devices and photovoltaics. While it is relatively straightforward to obtain a UPS spectrum in a laboratory photoelectron spectrometer equipped with an ultraviolet discharge lamp, obtaining a meaningful spectrum is more difficult and depends on various factors, including proper sample preparation and the elimination of surface charging. The basics of the technique, along with procedures for proper measurement of valence spectra of bare and adsorbate-covered metal and semiconducting surfaces, and conjugated polymer/oligomer films, are described. Best practices for presenting UPS data and measuring work functions from UPS spectra are also discussed.

Ozone, heating-in-air, and chromic acid treatments of polypropylene (PP) films and fibers were evaluated for their ability to promote ZnO nanoparticle (NP) adhesion. X-ray photoelectron spectroscopy (XPS) demonstrated that the oxygen content of the surface of PP films increased due to all treatments, with high binding energy O1s components emerging consistent with carbonyl, carboxylic acid, ester and hydroperoxide groups. The latter two were dominant for chromic acid treatment. The XPS measurements were complemented by attenuated total reflectance FTIR spectroscopy studies. Pull-off measurements from PP films, using a ZnO particle attached to the cantilever of an atomic force microscope, indicated that ozone and chromic acid treatments were equally effective at increasing adhesive forces. However, scanning electron microscopy studies of PP fibers treated with either ozone or chromic acid, and subsequent immersion in an ethanolic ZnO NP suspension, showed that ozone treatment was more effective than chromic acid treatment at promoting adhesion. This likely results from the poorer ability of ester and hydroperoxide groups, compared to carboxylic acid ones, to bind to hydroxylated ZnO NPs. It was further shown that excessive ozone treatment leads to brittleness of the fibers, as evidenced by cracking when the fibers are stirred. These results indicate that moderate ozone treatment of PP films and fibers may be a convenient method to attach metal oxide particles to PP surfaces.

Fibers and fabrics whose surfaces are decorated with metal oxide particles are finding important applications, including antimicrobial, filtration, and catalytic ones. In the present study, a very simple method has been developed to functionalize polypropylene (PP) surfaces, including those of fibers, with metal oxide nanoparticles (NPs). Extruded fibers and spin-coated films have been prepared from solid mixtures of PP and zinc oxide NPs using either 12 or 250 kDa PP (PP12k and PP250k, respectively). In the case of PP12k films containing 5 wt % ZnO, the segregation of the NPs to the polymer-air interface is detected by the emergence of Zn2p X-ray photoelectron spectroscopy (XPS) signal after either room temperature ozone exposure or annealing at 140 degrees C in an oxygen-containing atmosphere. For PP250k films, ozone exposure without heating does not induce surface segregation; however, it does occur upon annealing at 160 degrees C in an oxygen-containing atmosphere. Annealing in air causes the atomic percentages of Zn detected by XPS to increase from 0 to 0.22 and 0.34% for the PP12k and PP250K films, respectively. Cross-sectional scanning electron microscopy of a 3 wt % ZnO in PP12k fiber shows that NP migration to the surface does not deplete the bulk of ZnO, implying that the migration of NPs to the surface occurs from the near-surface region. Adsorption of a phosphonated dye, flavin mononucleotide, on surface-segregated films and fibers is confirmed by fluorescence microscopy, indicating that the ZnO NPs are available for surface reactions. XPS and Fourier transform infrared spectroscopy of PP exposed to ozone or heated in air demonstrate the presence of ketone and carboxylic acid functional groups. Heating of a ZnO surface-segregated PP12k film in ultrahigh vacuum to partially reverse oxidation also reverses surface segregation. It is postulated that surface segregation is enthalpically driven by the attraction of the ZnO NPs to the polar surface functional groups. This work may be useful for the preparation of fibers and fabrics for catalysis/photocatalysis applications.

Gold and lithium have been deposited on clean, stoichiometric TiO2(110) to study the evolution of the electronic structure of the surface. For thermally deposited gold, X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) indicate that the first monolayer (ML) grows two dimensionally, while additional gold forms islands, and that the surface becomes metallic by 1 ML. Downward band bending for low coverage is confirmed by a comparison of the XPS valence and UPS spectra, which have different detection depths. Inverse photoelectron spectroscopy (IPES) shows that the deposited gold attenuates the Ti 3d states, which dominate the conduction band. In the case of lithium, XPS analysis indicates that deposited atoms penetrate into the bulk, with a gradual buildup in the near-surface region. UPS shows the formation of a Ti3+ 3d gap state 1.4 eV below the Fermi level. Band bending is not observed for low Li coverage due to pinning of the Fermi level to the gap state. Deposition of more than 10 ML is required for the work function to reach that of bulk Li. Unoccupied 3d states disappear from the IPES spectrum as they are filled by electrons injected from Li.

The adsorption of 2-naphthalenethiol (2-NPT) and methanethiol (MT) on 13 different metal oxide nanoparticles, of approximately 30 nm average primary particle size, has been investigated. In the case of 2-NPT, which is fluorescent, a screening method to assess adsorption was developed that consists of mixing the nanoparticles with a dilute ethanolic solution of 2-NPT and performing several cycles of centrifuging and rinsing with ethanol. Fluorescence measurements on the re-dispersed particle suspensions were then used to diagnose whether or not adsorption had occurred. Complementary experiments were performed by mounting powder samples of each of the metal oxide nanoparticles onto sample stubs and performing X-ray photoelectron spectroscopy (XPS) before and after in situ dosing with MT. In both cases, adsorption was observed only on ZnO, TiO2, and In2O3. Adsorption did not occur on Al2O3, CeO2, Fe2O3, Gd2O3, Ho2O3, NiO, SiOx, WO3, Y2O3, and ZrO2. Density functional theory (DFT) calculations were performed using small metal oxide clusters, assuming that dissociative adsorption occurs by replacement of a hydroxyl group attached to a metal site and the formation of water. The theoretical and experimental results generally agree, suggesting that this is indeed the adsorption mechanism for most of the nanoparticles. The agreement also suggests that the size and geometry of the nanoclusters play a minor role and that the relative strengths of the metal-sulfur and metal-hydroxyl bonds dictate thiol adsorption. This work has important implications related to the functionalization of metal oxide nanoparticles and surfaces.

Tungsten oxide (WO3) nanoparticles, with an average size of ca. 50 nm, dramatically change color from light to dark green upon methanethiol (MT) exposure. Proton NMR indicates the presence of physisorbed MT and its oxidation product, dimethyldisulfide. X-ray photoelectron spectroscopy indicates that a maximum of ca. 33% of the W6+ is reduced to W5+ in the process of MT oxidation with creation of oxygen vacancies. Raman spectroscopy shows negligible changes in lattice vibrations, consistent with absence of proton insertion. These results demonstrate that the color change is due to W5+ to W6+ intervalence transitions and support an oxygen vacancy mechanism.

Random and block N-isopropylacrylamide (NIPAM)/cysteamine copolymers and a thiol-terminated NIPAM homopolymer have been synthesized, characterized, and covalently linked to gold nanoparticles. Electrical conductivities of their films have been measured as a function of temperature and laser irradiation wavelength in the presence of water, methanol, and hexanes vapors. For the homopolymer composite, the distance between particles is so large that the conductivity is negligible. For the block copolymer composite, changes in dielectric constant dominate film conductivity due to coating of the gold particles. The random copolymer composite film changes conductivity dramatically in the presence of water and methanol vapors upon heating because of swelling/shrinking of the NIPAM. Laser irradiation with light matching the energy of the surface plasmon resonance of the gold nanoparticles causes dramatic changes in the conductivity of the composite film in the presence of water vapor. However, minimal changes occu...

Photoluminescence (PL) changes of ZnO nano spheres at room temperature have been measured during exposure to gases and vapors using a traditional fluorometer and a portable, ultraviolet (UV) light-emitting diode-based instrument. Thermal gravimetric analysis indicates that the nanospheres are essentially fully hydroxylated, with OH groups and H atoms attached to surface Zn and O sites, respectively. The PL spectrum has both a UV excitonic emission peak and a visible, defect-related one. Exposure to the gases and vapors studied, whether they physisorb or chemisorb, causes a decrease in the intensity of the visible emission peak relative to pure nitrogen, although to different degrees. Electron-donating molecules, such as hydrogen and methanol, cause a reversible increase in the UV emission peak intensity due to formation of an electron-rich accumulation layer around the nanoparticles. Electron-withdrawing molecules, such as oxygen and water, cause a corresponding decrease due to a depletion layer. For reactive adsorption, such as by sulfur dioxide and methanethiol (MT), surface hydroxyl groups play an important role in reactivity and PL changes. X-ray photoelectron spectroscopy, coupled with density functional theory calculations, confirms that MT adsorption occurs by replacement of hydroxyl groups adsorbed on Zn sites, while SO2 adsorption leads to sulfite formation and removal of H atoms attached to O sites. The latter process causes a more dramatic decrease in visible emission, and it is postulated that hydroxyl groups formed by adsorbed H on O sites act as efficient charge traps that enhance visible PL. Their removal decreases visible PL, partially shutting down this energy pathway and causing an increase in UV emission. While SO2 and MT adsorption occur mainly by replacement of surface hydroxyls, benzene adsorbs at defect sites, such as oxygen vacancies. HCI and Cl-2 decrease the visible and UV emission peaks by transforming the surface of the ZnO to ZnCl2, while H2S causes the emergence of a PL peak at 422 nm, which is postulated to arise from the formation of Zn interstitial defects.

Experiments conducted during the last several decades demonstrate that multilayers of aromatic molecules cryogenically condensed on surfaces may be polymerized by X-rays, low-energy electrons, and in some cases ultraviolet (UV) light. The majority of studies indicate that photoelectrons and secondary electrons from the substrate are responsible for the process, as opposed to direct interaction of the photons or electrons with the aromatic molecules. UV photoelectron spectroscopy shows that π conjugation exists in the irradiated films, which may be up to several microns in thickness, and that the films are oligomeric, consisting of chains that are likely less than six units long. Thiophene and its derivatives have been the most widely studied class of aromatic molecules. In the case of 3-hexylthiophene, fluorescence measurements of beam-formed films support the conclusion that they are oligomeric. Some cross-linking is indicated by Fourier transform infrared (FTIR) spectroscopy of the films, and they appear similar to those obtained by electrochemical polymerization. Extensive electron or X-ray irradiation of thiophene, benzene, and other aromatic molecules eventually results in graphitic carbon, and forming graphene from a monolayer or a few layers of condensed molecules may be achieved. Patterns of conjugated oligomers may be formed either by using a focused electron beam or, for nanoscale lithography, a scanning tunneling microscope (STM) operating in field-emission mode. An STM tip operating in tunneling mode may also induce oligomerization by multiple-quantum transitions, such as vibrational excitation and C H bond cleavage. In the case of self-assembled monolayers with aromatic tail groups, electron irradiation may lead to cross-linking, with applications in resist formation. Possible mechanisms for photon- and electron-induced oligomerization are also discussed.