Specific Adsorption Sites Research Articles

Flower-like tin oxide membranes with robust three-dimensional channels for efficient removal of iron ions from hydrogen peroxide

Membrane technology has become the mainstream process for the production of electronic grade hydrogen peroxide (H2O2). But due to the oxidation degradation of the organic membranes (e.g. polyamide) by the strong oxidative radicals (e.g. OH) generated via the activation of H2O2 by iron ions (Fe3+), the short effective lifetime of membranes remains a challenge. Inorganic nano tin oxide (SnO2) has great potential for the removal of Fe3+ in strongly oxidative H2O2 because of its ability to stabilize H2O2 and preferentially adsorb Fe3+. Herein, we have designed for the first time a flower-like robust SnO2 membrane on the ceramic support by in situ template-free one-step hydrothermal method. The three-dimensional loose pore structure in the membrane built by interlacing SnO2 nanosheets endows the SnO2 membrane with a high specific surface area and abundant adsorption sites (OH). Based on the coordination complexation and electrostatic attraction between the SnO2 surface and Fe3+, the membrane shows a high Fe3+ removal efficiency (83%) and permeability (24 L·m−2·h−1·MPa−1) in H2O2. This study provides an innovative and simple approach to designing robust SnO2 membranes for highly efficient removal of Fe3+ in harsh environments, such as strong oxidation conditions.

High performance Hetero-Shelled hollow structure Metal-Organic framework hybrid material for the efficient electrochemical determination of lead ions

Electrochemical sensing has unique advantages in developing on-site and online detection technologies for heavy metal ions (HMIs) due to its fast response, simple operation, high sensitivity, and portable instruments. The vigorous development of modern micro/nanomaterial preparation technology has provided greater space for improving the performance of electrochemical sensing platforms. In this work, a novel hetero-shelled hollow structure metal–organic framework (MOF) hybrid material (denoted as HCZ@UN) was prepared by adopting the hollow carbonized ZIF-8 (HCZ) as the substrate for growing UiO-66(Zr)–NH2 (UN), and subsequently used for efficient electrochemical detection of lead ions (Pb2+). The grown UN crystal particles were anchored on the HCZ hollow cages and showed nanometer size. The unique shell structure and nanometer size of UN created large specific surface area and rich accessible adsorption sites, which promoted the preconcentration of Pb2+. While the hollow carbon polyhedron structure of HCZ improved the dispersibility of UN and electron transfer ability of the material. These factors synergistically improved the detection sensitivity and sensing performance for Pb2+ determination with a wide linear range of 0.100–500 nM, a low detection limit of 0.0492 ± 0.00523 nM as well as good selectivity, repeatability and long-term stability. This paper provides a simple and effective method for the preparation of electroactive MOF functional materials, which is expected to inspire more interest in building other MOF-based materials with unique structure, high-performance and extensive application value.

Removal of Paracetamol and Cu2+ from Water by Using Porous Carbons Derived from Agrowastes

Dende and babassu coconuts are largely used in tropical countries, namely in Brazil, for the extraction of oils from kernels. The remaining biowastes are industrially processed to produce porous carbons (PCs). PCs derived from dende and babassu biowastes and produced at an industrial scale have been characterized by textural, chemical, and ecotoxicological parameters. A commercial activated carbon (CC) of mineral origin has been used as a benchmarking material. Although the CC sample presented a higher surface area (SBET = 1083 m2/g), the PCs derived from the biowastes were richer in micropores (Vmicro = 0.25–0.26 cm3/g), while the CC carbon presented wider pore size distribution with a higher mesopore volume (Vmeso = 0.41 cm3/g). All the adsorbents used in this work have shown a non-acute ecotoxic behavior for the bacterium Vibrio fischeri (EC50-30 min > 99% v/v). The adsorbents have been tested for paracetamol and Cu2+ adsorption in mono- and bicomponent solutions. The uptake capacities of paracetamol (qe, 98–123 mg g−1) and Cu2+ (qe, 15–18 mg g−1) from monocomponent solutions were similar to the ones obtained in the bicomponent solutions, indicating no competition or cooperative effects but a site-specific adsorption. This finding represents an advantage for the removal of these adsorbates when present in the same solution as they can be adsorbed under similar rates as in the single systems. Paracetamol adsorption was related to micropore filling, π-π interactions, and H-bonding, whereas Cu2+ removal was attributed to the cation exchange mechanism and complexation to the hydroxyl groups at the carbons’ surface.

Carboxyl-based deep eutectic solvent modified magnetic graphene oxide as a novel adsorbent for fast enrichment and extraction of estrogens in milk prior to HPLC-UV analysis

In this study, a magnetic graphene oxide modified with green carboxyl-based deep eutectic solvent (MGO@DES) was synthesized for the first time and employed as a highly efficient adsorbent for the magnetic solid-phase extraction (MSPE) of three estrogens in milk samples. With large specific surface, good hydrophobicity and abundant adsorption sites, MGO@DES exhibited excellent extraction performance for estrogens. The adsorption kinetic experiment revealed that 5 mg of MGO@DES reached the equilibrium of estrogen adsorption within 3 min. MGO@DES based MSPE coupled with HPLC-UV method was developed and applied to the determination of three estrogens in milk samples. Good linearity (R2 > 0.9953) was obtained in the range of 1–200 ng mL−1 and the low limits of detection were 0.20–0.28 ng mL−1. The spiked recoveries were in the range of 90.3–105.7%, with RSDs less than 7.9%.

Electron-Donor Functional Groups, Band Gap Tailoring, and Efficient Charge Separation: Three Keys To Improve the Gaseous Iodine Uptake in MOF Materials.

Metal-organic frameworks (MOFs) have been largely investigated worldwide for their use in the capture of radioactive iodine due to its potential release during nuclear accident events and reprocessing of nuclear fuel. The present work deals with the capture of gaseous I2 under a continuous flow and its subsequent transformation into I3- within the porous structures of three distinct, yet structurally related, terephthalate-based MOFs: MIL-125(Ti), MIL-125(Ti)_NH2, and CAU-1(Al)_NH2. The synthesized materials exhibited specific surface areas (SSAs) with similar order of magnitude: 1207, 1099, and 1110 m2 g-1 for MIL-125(Ti), MIL-125(Ti)_NH2, and CAU-1(Al)_NH2, respectively. Because of that, it was possible to evaluate the influence of other variables over the iodine uptake capacity─such as band gap energies, functional groups, and charge transfer complexes (CTC). After 72 h of contact with the I2 gas flow, MIL-125(Ti)_NH2 was able to trap 11.0 mol mol-1 of I2, followed by MIL-125(Ti) (8.7 mol mol-1), and by CAU-1(Al)_NH2 (4.2 mol mol-1). The enhanced ability to retain I2 in the MIL-125(Ti)_NH2 was associated with a combined effect between its amino group (which has a great affinity toward iodine), its smaller band gap (2.5 eV against 2.6 and 3.8 eV for CAU-1(Al)_NH2 and MIL-125(Ti), respectively), and its efficient charge separation. In fact, the presence of a linker-to-metal charge transfer (LMCT) mechanism in MIL-125(Ti) compounds separates the photogenerated electrons and holes into the two distinct moieties of the MOF: the organic linker (which stabilizes the holes) and the oxy/hydroxy inorganic cluster (which stabilizes the electrons). This effect was observed using EPR spectroscopy, whereas the reduction of the Ti4+ cations into the paramagnetic Ti3+ species was evidenced after irradiation of the pristine Ti-based MOFs with UV light (<420 nm). In contrast, because CAU-1(Al)_NH2 exhibits a purely linker-based transition (LBT)─with no EPR signals related to Al paramagnetic species─it tends to exhibit faster recombination of the photogenerated charge carriers as, in this case, both electrons and holes are located over the organic linker. Furthermore, the transformation of the gaseous I2 into In- [n = 5, 7, 9, ...] intermediates and then into I3- species was evaluated using Raman spectroscopy by following the evolution of their respective bands at about 198, 180, and 113 cm-1. This conversion─which is favored by an effective charge separation and smaller band gaps─increases the I2 uptake capacity of the compounds by creating specific adsorption sites for these anionic species. In fact, because the -NH2 groups act as an antenna to stabilize the photogenerated holes, both In- and I3- are adsorbed into the organic linker via an electrostatic interaction with these positively charged entities. Finally, changes regarding the EPR spectra before and after the iodine loading were considered to propose a mechanism for the electron transfer from the MOFs structure to the I2 molecules considering their different characteristics.

Hollow-structured molecularly imprinted polymers enabled specific enrichment and highly sensitive determination of aflatoxin B1 and sterigmatocystin against complex sample matrix

The biotoxins with high toxicity have the potential to be manufactured into biochemical weapons, seriously threatening international public security. Developing robust and applicable sample pretreatment platforms and reliable quantification methods has been recognized as the most promising and practical approach to solving these problems. Through the integration of the hollow-structured microporous organic networks (HMONs) as the imprinting carriers, we proposed a molecular imprinting platform (HMON@MIP) with enhanced adsorption performance in terms of specificity, imprinting cavity density as well as adsorption capacity. The HMONs core of MIPs provided a hydrophobic surface that enhanced the adsorption of biotoxin template molecules during the imprinting process, resulting in an increased imprinting cavity density. The HMON@MIP adsorption platform could produce a series of MIP adsorbents by changing the biotoxin template, such as aflatoxin and sterigmatocystin, and showed promising generalizability. The limits of detection (LOD) of the HMON@MIP-based preconcentration method for AFT B1 and ST were 4.4 and 6.7 ng L−1, respectively, and the method was applicable to food sample with satisfied recoveries of 81.2–95.1%. And the specific recognition and adsorption sites left on HMON@MIP by the imprinting process can achieve outstanding selectivity for AFT B1 and ST. The developed imprinting platforms hold great potential for application in the identification and determination of various food hazards in complex food sample matrices and contribute to precise food safety inspection.

Type-wide biochars loaded with Mg/Al layered double hydroxide as adsorbent for phosphate and mixed heavy metal ions in water

This study discussed the adsorption of mixed heavy metal ions (Cu2+, Co2+, Pb2+) and phosphate ions by ten pristine biochars and those with precipitated Mg/Al layered double hydroxide (LDH). The pristine biochars have adsorption capacities of 6.9–13.4 mg/g for Cu2+, 1.1−9.7 mg/g for Co2+, 7.8−20.7 mg/g for Pb2+, and 0.8−4.9 mg/g for PO43−. The LDH-biochars have markedly increased adsorption capacities of 20.4–25.8 mg/g for Cu2+, 8.6−15.0 mg/g for Co2+, 26.5−40.4 mg/g for Pb2+ with mixed metal ions, and 13.0−21.8 mg/g for PO43−. Part of the Mg ions but Al ions are released from the LDH-biochars during adsorption, counting less than 7.2% of the adsorbed ions. The pristine biochars have specific adsorption sites for Cu2+ and Co2+, separate Pb2+ sites related to ether groups on biochar, and areal-dependent sites for PO43−. There is no universal adsorption mechanism corresponding to mixed metal ion adsorption for individual pristine biochar involving different contributions of C–O–C, C–O–H, and CO groups and graphitic-N, pyrrolic-N, and pyridine-N groups. The LDH complexes with hydroxyl and carbonyl groups of biochar, and the LDH interacts with biochar's ether groups, which contributes to metal adsorption, against the conception that the biochar is merely a carrier of LDH as adsorbents.

Recent Applications of Carbon Nanotubes for Separation and Enrichment of Lead Ions

Lead is one of the most toxic heavy metals released into the environment through industrial sources. Its direct determination is often a problem due to the presence of relatively complex matrices as well as low content. Thus, the additional separation and preconcentration steps are necessary in the analytical procedures. Carbon nanotubes (CNTs) continue to attract significant interest for these purposes as they exhibit a high specific surface area, exceptional porosities, and numerous adsorption sites. The modified CNTs with active groups, reagents, or materials have been widely explored using more mutual interactions that can significantly improve their sorption capacity and selectivity. This paper summarizes the recent developments from 2017 in the application of carbon nanotubes for the separation of Pb(II) and its enrichment/removal from the matrix components. Attention is given to oxidized CNTs, their modification with complexing compounds, functionalization with metal oxides and polymers, new nanocomposites, and carbon nanotube membranes.

Chiral and Catalytic Effects of Site-Specific Molecular Adsorption.

The changes of properties and preferential interactions based on subtle energetic differences are important characteristics of organic molecules, particularly for their functionalities in biological systems. Only slightly energetically favored interactions are important for the molecular adsorption and bonding to surfaces, which define their properties for further technological applications. Here, prochiral tetracenothiophene molecules are adsorbed on the Cu(111) surface. The chiral adsorption configurations are determined by Scanning Tunneling Microscopy studies and confirmed by first-principles calculations. Remarkably, the selection of the adsorption sites by chemically different moieties of the molecules is dictated by the arrangement of the atoms in the first and second surface layers. Furthermore, we have investigated the thermal effects on the direct desulfurization reaction that occurs under the catalytic activity of the Cu substrate. This reaction leads to a product that is covalently bound to the surface in chiral configurations.

Non-reactive facet specific adsorption as a route to remediation of chlorinated organic contaminants

The present work quantifies metal-contaminant interactions between palladium substrates and three salient chlorinated organic contaminants, namely trichloroethylene 1,3,5-trichlorobenzene (TCB), and 3,3′,4,4′-tetrachlorobiphenyl (PCB77). Given that Pd is one of the conventional catalytically active materials known for contaminant removal, maximizing catalytic efficiency through optimal adsorption dynamics reduces the cost of remediation of contaminants that are persistent water pollutants chronically affecting public health. Adsorption efficiency analyses from all-atom molecular dynamics (MD) simulations advance the understanding of reaction mechanisms available from density functional theory (DFT) calculations to an extractable feature scale that can fit the parametric design of supported metal catalytic systems and feed into high throughput catalyst selection. Data on residence time, site-specific adsorption, binding energies, packing geometries, orientation profiles, and the effect of adsorbate size show the anomalous behaviour of organic contaminant adsorption on the undercoordinated {110} surface as compared to the {111} and {100} surfaces. The intermolecular interaction within contaminants from molecular dynamics simulation exhibits refreshing results than ordinary single molecule density functional theory calculation. Since complete adsorption and dechlorination is an essential step for chlorinated organic contaminant remediation pathways, the presented profiles provide essential information for designing efficient remediation systems through facet-controlled palladium nanoparticles.

Preparation and performance of UiO‐66‐(COOH)2‐based mixed matrix membranes for efficient separation of Sr2+ ions from aqueous solutions

AbstractBACKGROUNDDeveloping new materials for separating Sr2+ ions from aqueous solutions is significant. Metal–organic frameworks are regarded as excellent adsorption materials due to their high specific surface area and abundant adsorption sites. In this work, a novel UiO‐66‐(COOH)2‐based mixed matrix membrane (MMM) was prepared by combining UiO‐66‐(COOH)2 with polyethersulfone (PES) for separating Sr2+.RESULTSThe MMMs were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy and water contact angle and water flux measurements. Various contents (0–2.5 wt%) of UiO‐66‐(COOH)2 were blended into PES membranes. The results showed that incorporating UiO‐66‐(COOH)2 significantly increased membrane porosity and water flux, and reduced contact angle. The membrane (M4) that contained 2.0 wt% UiO‐66‐(COOH)2 exhibited an excellent morphology and the highest Sr2+ uptake capacity (111.9 μg cm−2). Adsorption kinetics and isotherms showed that the nature of the adsorption of the membrane towards Sr2+ was chemisorption, homogeneous and monolayer. Compared with the adsorption capacity of UiO‐66‐(COOH)2 towards Sr2+ in adsorption packed column, these values of M4 decreased by about 75% during membrane filtration. The rejection performance of MMMs increased with increasing UiO‐66‐(COOH)2 content. Breakthrough curves of MMMs were not correlated with flow rate in the range of 10–180 mL h−1. The presence of Ca2+ and Mg2+ ions did not obviously affect the separation of Sr2+, but Pb2+ had a significant influence. Furthermore, after five adsorption–desorption experiments, the regeneration remained at about 95% of initial values.CONCLUSIONSThe MMMs showed good adsorption capacity for Sr2+ and exhibited favorable reusability and stability. © 2023 Society of Chemical Industry (SCI).

Delineating the Effects of Molecular and Colloidal Interactions of Dissolved Organic Matter on Titania Photocatalysis.

In the face of significant challenges to practical applications of photocatalysis for water treatment, recent reports revealed a potential route to overcome a problem posed by dissolved organic matter (DOM). These studies showed that inhibition of photocatalytic processes by DOM is driven largely by competition for active surface sites on TiO2 or other catalysts, and controlling the type of DOM present in solution could significantly mitigate DOM fouling. Whether or not control of solution parameters could achieve the same preventative action is not known. Here, a series of DOM isolates, including humic acid (HA) and transphilic (TPI), hydrophobic (HPO), or colloidal fractions of organic matter from a membrane bioreactor mixed liquor supernatant, were tested for inhibitory activity under a range of pH values (3, 5, 7, and 9) and ionic compositions (NaCl, CaCl2, and Al2(SO4)3 with ionic strengths (IS) ranging from 0 to 3 M). The resulting TiO2-DOM agglomerates were monitored for size and ζ-potential. Inhibitory profiles were generated using para-chlorobenzoic acid (pCBA) as probe with varying concentrations of inhibitory DOM for each solution condition to discern the extent of surface-phase quenching of radicals. Manipulation of pH clearly impacted inhibition, and the effect varied by DOM type; for example, interference occurred at all pHs for HA, at neutral or basic pHs for TPI, and only at pH 7 for HPO. Particle sizes did not correlate with inhibitory action of DOM. Increases in ionic strength induced growth of TiO2 and TiO2-DOM agglomerates, but again, particle sizes did not correlate to inhibition by DOM. The changes to IS, regardless of ion type, were not affected by the presence of TPI or HPO. Since particle stability did not correlate directly with photocatalytic activity, we suggest that surface-based quenching reactions arise from site-specific adsorption rather than generalized particle destabilization and aggregation.

Classical and new insights into the methodology for characterizing adsorbents and metal catalysts by chemical adsorption

The adsorption phenomenon has been used extensively to achieve and explain solid-state reactions, control contamination, and purify liquids and gases. This process implies the use of a porous medium or a material with specific adsorption centers where the interactions with the reagents occur. Determination of the properties of adsorbent or catalyst materials that do not contain specific adsorption sites by physical gas adsorption is a well-established procedure in most research and quality-control laboratories. However, characterizing the specific centers by selective adsorption—chemisorption—remains an open question for discussion and study. The specific centers involved are often acidic/basic and metallic; in most cases, reagents are adsorbed and desorbed in these centers, whose determination allows controlling the processes and comparing the materials. The techniques and procedures presented herein facilitate the evaluation and the qualitative and quantitative determination of the surface properties of the materials using chemisorption processes for metallic and acidic/basic sites. The aim of this work is to review these techniques and procedures, including the updates published by several researchers, who mostly strive to explain the results of bifunctional metallic and acid–base catalytic behavior.

Synthesis of a pyridine-based covalent organic framework as an efficient adsorbent for rhodamine B removal.

Covalent organic frameworks (COFs), featured with crystalline structures, permanent porosity, and designable organic skeletons, are good candidates for serving as adsorbents. Herein, a new pyridine-based two-dimensional COF (TAPP-DBTA-COF) was constructed via the condensation of 2,4,6-tris(4-aminophenyl)pyridine and 2,5-dibromobenzene-1,4-dicarbaldehyde. TAPP-DBTA-COF displayed high-performance for the removal of rhodamine B (Rh B) from water with high capacity, good adaptability and reusability. The maximum adsorption capacity for Rh B can reach up to 1254 mg g-1, and the kinetic constant was determined as k2 = 0.00244 g mg-1 min-1. Moreover, the corresponding amorphous polymer of TAPP-DBTA-COF, termed as TAPP-DBTA-COP, was synthesized from the same starting materials. The lower efficiency of TAPP-DBTA-COP in capture of Rh B revealed that the ordered pore structure, large specific surface area and rich adsorption sites play an important role in adsorption.

Site-specific ammonia adsorption and transduction on a naphthalimide derivative molecule - a complementary analysis involving ab initio calculation and experimental verification.

Naphthalene diimide derivatives (NDIs) have exhibited significant potential for sensing applications owing to their excellent photo-stability, environmental stability, reasonable electronic conductivity, and ability to form nanostructures with diverse morphologies through self-assembly. However, no systematic analysis has been performed to rationalize molecular-level interactions between ammonia (NH3) and functionalized NDI probes, which is essential for systematic performance optimizations of NDI-based NH3 sensors. Therefore, this work proposes a phenylalanine-functionalized NDI derivative (NDI-PHE) as a model host for NH3 adsorption. Subsequent molecular interactions have been comprehensively studied following a complementary approach using ab initio calculation and experimental investigation. Specifically, NH3 adsorption at different atomic positions of NDI-PHE has been investigated using ab initio calculation, where the adsorption energy, charge transfer, and recovery time have been emphasized. The environmental stability of NDI-PHE and the underlying transduction mechanism during NH3 adsorption have been experimentally demonstrated to complement the theoretical analysis. The results exhibit that the presence of phenylalanine groups acts as an anchoring moiety and augments NH3 adsorption via hydrogen bonding and proton transfer interaction. Specifically, a highly stable room temperature adsorption of NH3 near a carboxylic phenylalanine group has been observed with a suitable recovery time at higher temperatures. NH3 adsorption results in electron transfer to the host molecule leading to the formation of stable radical anion species, which significantly modulated the frontal molecular orbitals of NDI-PHE, suggesting superior transduction for both electrochemical and optical detection.

MOF/MWCNT-Nanocomposite Manipulates High Selectivity to Gas via Different Adsorption Sites with Varying Electron Affinity: A Study in Methane Detection in Parts-per-Billion.

Metal-organic frameworks (MOFs) present specific adsorption sites with varying electron affinity which are uniquely conducive to selective gas sensing but are typically large-band-gap insulators. On the contrary, multiwall carbon nanotubes (MWCNTs) exhibit superior mesoscopic transport exploiting strong electron correlations among sub-bands below and above the Fermi level at room temperature. We synergize them in a new class of nanocomposites based on zeolitic imidazolate framework-8 (ZIF-8) and report selective sensing of CH4 in ∼10 parts-per-billion (ppb) with a determined limit of detection of ∼0.22 ppb, hitherto unprecedented. The observed selectivity to CH4 over non-polar CO2, polar volatile organic compounds, and moisture has roots in competing electron-sharing mechanisms at its different adsorption sites. This important result provides a significant reference to guide future MOF-related composite research to achieve the best sensing performance. On molecular adsorption, MWCNTs facilitate electrical transport via manipulating the ZIF-8 band gap to show a p-type semiconductor behavior with lower activation energy to induce a measurable resistance change. Excellent repeatability and reversibility are shown. A carbon-engineered MOF composite has the potential to actuate similar selective response to low reactive gases via carrier manipulation in the energy band gap.

Highly efficient detection of Pb(II) ion in water by polypyrrole and metal-organic frame modify glassy carbon electrode

Since lead is teratogenic, carcinogenic and mutagenic, people pay increasing attention to lead contamination in water environment. In this work, a novel electrochemical sensor was developed to detect Pb(II) ion in water by PPy, MOFs and bismuth film (BF) modify GCE. Scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, electrochemical impedance spectroscopy, contact angleanalyses, cyclic voltammetry and differential pulse anodic stripping voltammetry were used to characterize the BF-PPy/UIO-66-NH 2 /GCE surface, revealing the physical and electrochemical properties of the electrode. MOFs increased the specific surface area and adsorption site of the electrode. The PPy enhanced the conductivity of the composites materials. MOFs and PPy synergistically promoted the electrochemical performance of the electrode. The deposition potential, deposition time, solution pH and Bi (III) concentration were optimized to determine the optimal detection condition. The electrode has a wide linear range (0.5 to 10 μg/L) with a low detection limit (0.05 μg/L). This electrode also has good anti-interference, repeatability and stability. Besides, it has been successfully applied to the detection of actual water samples. The recovery rates ranged from 95.4 % to 102.8 % with a relative standard deviation (RSD) less than 4.40 %. Our results provide an insight on efficient and rapid detection of Pb(II) ions in water environment in the future. • MOFs and polypyrrole synergistically promoted the electrochemical performance. • The fabricated BF-PPy/UIO-66-NH 2 /GCE shows a low Pb(II) detection limit. • This sensor was applied to the detection of Pb(II) in tap water and groundwater.

In Situ Growth Intercalation Structure MXene@Anatase/Rutile TiO2 Ternary Heterojunction with Excellent Phosphoprotein Detection in Sweat.

Abnormal protein phosphorylation may relate to diseases such as Alzheimer’s, schizophrenia, and Parkinson’s. Therefore, the real-time detection of phosphoproteins in sweat was of great significance for the early knowledge, detection, and treatment of neurological diseases. In this work, anatase/rutile TiO2 was in situ grown on the MXene surface to constructing the intercalation structure MXene@anatase/rutile TiO2 ternary heterostructure as a sensing platform for detecting phosphoprotein in sweat. Here, the intercalation structure of MXene acted as electron and diffusion channels for phosphoproteins. The in situ grown anatase/rutile TiO2 with n-n-type heterostructure provided specific adsorption sites for the phosphoproteins. The determination of phosphoprotein covered concentrations in sweat, with linear range from 0.01 to 1 mg/mL, along with a low LOD of 1.52 μM. It is worth noting that, since the macromolecular phosphoprotein was adsorbed on the surface of the material, the electrochemical signal gradually decreased with the increase of phosphoprotein concentration. In addition, the active sites in the MXene@anatase/rutile TiO2 ternary heterojunction and synergistic effect of the heterojunction were verified by first-principle calculations to further realize the response to phosphoproteins. Additionally, the effective diffusion capacity and mobility of phosphoprotein molecules in the ternary heterojunction structure were studied by molecular dynamics simulation. Furthermore, the constructed sensing platform showed high selectivity, repeatability, reproducibility, and stability, and this newly developed sensor can detect for phosphoprotein in actual sweat samples. This satisfactory sensing strategy could be promoted to realize the noninvasive and continuous detection of sweat.

Infrared-to-visible upconversion enhanced photothermal catalytic degradation of toluene over Yb3+, Er3+: CeO2/attapulgite nanocomposite: Effect of rare earth doping

Developing low cost and efficient strategy to eliminate volatile organic compounds (VOCs) are quite urgent and challenging. Herein, CeO2 nanoparticles co-doped with Yb3+ and Er3+ were immobilized on attapulgite clay (ATP) for photothermal catalytic oxidation of toluene. The CeO2:Yb3+, Er3+/ATP exhibited outstanding catalytic activity with low T90 of 295 °C (temperature at 90% degradation), satisfactory stability and highly water resistance. The enhanced photothermal catalytic performance can be attributed to the optimal introduction of Yb3+ and Er3+, which promoted the up-conversion of near-infrared light (NIR) to visible light increasing the light utilization. The defects caused by Yb3+/Er3+ doping facilitated the adsorption of O2, while the active oxygen species generated from the defects and the photoinduced reactive species not only favored the oxidation of toluene in photothermal catalytic process, but also accelerated the reoxidation of reduced catalyst. Notably ATP support provided large specific surface area and abundant adsorption sites for toluene molecules to promote the deep oxidation and hindered the deactivation of catalysts caused by the accumulation of intermediates. In-situ DRIFTS test revealed that the alkoxide and benzoate appeared as the main intermediates, which can be deeply oxidized under light irradiation. Current work provides a new alternative for photothermal catalytic degradation of VOCs.

Deposition of Chiral Heptahelicene Molecules on Ferromagnetic Co and Fe Thin-Film Substrates.

The discovery of chirality-induced spin selectivity (CISS), resulting from an interaction between the electron spin and handedness of chiral molecules, has sparked interest in surface-adsorbed chiral molecules due to potential applications in spintronics, enantioseparation, and enantioselective chemical or biological processes. We study the deposition of chiral heptahelicene by sublimation under ultra-high vacuum onto bare Cu(111), Co bilayer nanoislands on Cu(111), and Fe bilayers on W(110) by low-temperature spin-polarized scanning tunneling microscopy/spectroscopy (STM/STS). In all cases, the molecules remain intact and adsorb with the proximal phenanthrene group aligned parallel to the surface. Three degenerate in-plane orientations on Cu(111) and Co(111), reflecting substrate symmetry, and only two on Fe(110), i.e., fewer than symmetry permits, indicate a specific adsorption site for each substrate. Heptahelicene physisorbs on Cu(111) but chemisorbs on Co(111) and Fe(110) bilayers, which nevertheless remain for the sub-monolayer coverage ferromagnetic and magnetized out-of-plane. We are able to determine the handedness of individual molecules chemisorbed on Fe(110) and Co(111), as previously reported for less reactive Cu(111). The demonstrated deposition control and STM/STS imaging capabilities for heptahelicene on Co/Cu(111) and Fe/W(110) substrate systems lay the foundation for studying CISS in ultra-high vacuum and on the microscopic level of single molecules in controlled atomic configurations.