Adsorption Of Molecules Research Articles

Stable Au(111) Hexagonal Reconstruction Induced by Perchlorinated Nanographene Molecules.

Surface reconstructions play a crucial role in surface science because of their influence on the adsorption and arrangement of molecules or nanoparticles. On the Au(111) surface, the herringbone reconstruction presents favorable anchoring at the elbow sites, where the highest reactivity is found. In this work, we deposited large organic perchlorinated molecules on a Au(111) surface via high-vacuum electrospray deposition. With noncontact atomic force microscopy measurements at room temperature, we studied the molecular structures formed on the surface before and after annealing at different temperatures. We found that a supramolecular layer is formed and that a hexagonal reconstruction of the Au(111) surface is induced. After high-temperature annealing, the molecules are removed, but the hexagonal Au(111) surface reconstruction is preserved. With the hexagonal Au(111) surface reconstruction, a periodic lattice of anchoring sites is formed.

Structural Design of Hybrid Manganese(II) Halides for High Quantum Efficiency and Specific Response to Methanol.

Manganese(II) halides have been a new generation of optoelectronic materials due to their fascinating luminescent properties, however, lacking specific solvent-responsive analogues with high quantum efficiency. Herein, we prepared three single crystals, [Pr(MIm)2][MnBr4] ([Pr(MIm)2]2+ = 1,3-di(methylimidazolium)-propane, Compound 1), [Pr(EIm)2][MnBr4] ([Pr(EIm)2]2+ = 1,3-di(ethylimidazolium)-propane, Compound 2), and [Bu(MIm)2][MnBr4] ([Bu(MIm)2]2+ = 1,4-di(methylimidazolium)-butane, Compound 3), where different Bola-type cations were chosen as organic components to separate [MnBr4]2- tetrahedrons. All three compounds emitted bright green light with excellent quantum yields of 95.3, 80.0, and 96.2%, benefiting from the large Mn···Mn distance. More interestingly, Compound 3 showed a highly selective response to methanol in a series of tested organic solvents, with a rapid and reversible change in emission color from green to red. The single crystal of [Bu(MIm)2][MnBr4]·CH3OH with red emission proved that the luminescence switching was attributed to the adsorption of CH3OH molecules into the lattice space in the form of the O-H···Br hydrogen bonds. To our knowledge, for tetrahedrally coordinated Mn(II) species, the reversible emission color switching between green and red triggered by a solvent without the change of coordination number is achieved for the first time, providing promising applications for the specific detection of methanol.

Solvent‐Engineering‐Assisted Ligand Exchange Strategy for High‐Efficiency AgBiS2 Quantum Dot Solar Cells

AbstractAs the initial synthesized colloidal quantum dots (CQDs) are generally capped with insulating ligands, ligand exchange strategies are essential in the fabrication of CQD films for solar cells, which can regulate the surface chemical states of CQDs to make them more suitable for thin‐film optoelectronic devices. However, uncontrollable surface adsorption of water molecules during the ligand exchange process introduces new defect sites, thereby impairing the resultant device performance, which attracts more efforts devoted to it but remains a puzzle. Here, we develop a solvent‐engineering‐assisted ligand exchange strategy to revamp the surface adsorption, improve the exchange efficiency, and modulate the surface chemistry for the environmentally friendly lead‐free silver bismuth disulfide (AgBiS2) CQDs. The optimized AgBiS2 CQD solar cells deliver an outstanding champion power conversion efficiency (PCE) of up to 8.95 % and improved long‐term stability. Our strategy is less environment‐dependent and can produce solar cells with negligible performance variance for several batches across several months. Our work demonstrates the critical role of solvents for ligand exchange in the surface chemistry of CQDs and the realization of high‐performance photovoltaic devices in a highly reproducible manner.

In situ regulating the interfacial work function of Ag doped Ni(OH)2 via trace of Fe2+ for efficient water splitting

Traditional approaches for tuning the water electrolysis performance of catalysts through manipulating their work function (WF) have primarily focused on the design of pre-catalysts prior to electrochemical test. Herein, an in situ interfacial WF modulation concept has been developed to synthesize the Fe modified nickel-based hydroxide electrocatalyst with enhanced OER (named as 0.168-FeO-Ag-Ni(OH)2/NF) and HER (0.168-FeH-Ag-Ni(OH)2/NF) activity. The modulator is trace amounts of Fe2+ in 1 M KOH, while the support comprises silver-modified nickel hydroxide, in which the Ag possesses a valence catalysis effect on Ni or Fe sites. Under optimized Fe2+ content, the deposition of Fe facilitates the release of the WF of Ag-Ni(OH)2/NF and accelerates the electron transfer between the catalyst and reaction intermediates. Meanwhile, the charge transfer from Fe to Ni sites coupled with the blue shift of d-band promote the adsorption of water molecules and the desorption of hydrogen protons, thereby accelerating the hydrogen evolution reaction kinetics. Consequently, the OER and HER activity of 0.168-FeO-Ag-Ni(OH)2/NF and 0.168-FeH-Ag-Ni(OH)2/NF enhanced 4.31 and 2.48 times, respectively. Notably, compared with Ag-Ni(OH)2/NF(+)//Ag-Ni(OH)2/NF(−), at a high current density of 1000 mA cm−2, the potential for energy consumption reduction of 0.168-FeO-Ag-Ni(OH)2/NF(+)//0.168-FeH-Ag-Ni(OH)2/NF(−) couple is at least 6 %, which endows it a promising application prospect in the actual electrolytic water system in the future.

Solvent-Engineering-Assisted Ligand Exchange Strategy for High-Efficiency AgBiS2 Quantum Dot Solar Cells.

As the initial synthesized colloidal quantum dots (CQDs) are generally capped with insulating ligands, ligand exchange strategies are essential in the fabrication of CQD films for solar cells, which can regulate the surface chemical states of CQDs to make them more suitable for thin-film optoelectronic devices. However, uncontrollable surface adsorption of water molecules during the ligand exchange process introduces new defect sites, thereby impairing the resultant device performance, which attracts more efforts devoted to it but remains a puzzle. Here, we develop a solvent-engineering-assisted ligand exchange strategy to revamp the surface adsorption, improve the exchange efficiency, and modulate the surface chemistry for the environmentally friendly lead-free silver bismuth disulfide (AgBiS2) CQDs. The optimized AgBiS2 CQD solar cells deliver an outstanding champion power conversion efficiency (PCE) of up to 8.95 % and improved long-term stability. Our strategy is less environment-dependent and can produce solar cells with negligible performance variance for several batches across several months. Our work demonstrates the critical role of solvents for ligand exchange in the surface chemistry of CQDs and the realization of high-performance photovoltaic devices in a highly reproducible manner.

Au, Ag, Pb, Pt −doped MoTe2 monolayer as a novel sensor for dissolved gases (CH4, and C2H2): A first-principles study

In this study, C2H2 and CH4 gas molecules adsorption on intrinsic MoTe2 and Au, Ag, Pb, Pt doped MoTe2 by density functional theory (DFT). The adsorption energy, bond length, charge transfer, PDOS and work function are calculated, it can be proved that Ag-MoTe2 have excellent C2H2 and CH4 adsorption performance than Au-MoTe2, Pb-MoTe2 and Pt-MoTe2. However, C2H2 gas molecule can be chemisorbed onto the doped Ag in the modified MoTe2 with a high adsorption energy of 0.923 eV, capturing approximately 0.65 e from the sensing material. Ag-MoTe2 has the better C2H2 and CH4 adsorption performance than Au-MoTe2, Pb-MoTe2 and Pt-MoTe2, as evidenced by the strong overlap of the s, p, d orbitals and the significant reduction of the energy gap from the PDOS. Therefore, suggesting that the Ag-MoTe2 could have potential application in the capture and dissociation of C2H2 and CH4.

Theoretical insights of 2D Fe3GeTe2/In2Se3 multiferroic vdW heterostructure based gas sensors for high-performance NO detecting

The impact of the harmful gas NO on the atmospheric environment cannot be ignored, so it is necessary to develop efficient gas sensors to detect and absorb NO at room temperature. In this work, we systematically explored the electron transport properties and gas sensing properties of Fe3GeTe2, In2Se3 monolayers and its multiferroic van der Waals (vdW) heterostructures of Fe3GeTe2/In2Se3 for detecting NO by using density functional theory and nonequilibrium Green's function methods. The calculated adsorption energies, electron localisation functions, band structures and density of states indicate that its a chemisorption for the adsorption of NO on Fe3GeTe2 and a physisorption on In2Se3, while the specific adsorption style is highly dependent on the stacking and molecular adsorption sites of different Fe3GeTe2/In2Se3 structures. In addition, the pristine Fe3GeTe2 monolayer and Fe3GeTe2/In2Se3 based nanodevices realized a significant anisotropy for electron transport along the zigzag and armchair directions, and their anisotropic maximum current ratios in the zigzag to armchair directions were 1.90 and 1.89. Meanwhile, the NO sensitivity ratio of Fe3GeTe2 and Fe3GeTe2/In2Se3 based gas sensors can be up to 79 % and 107 %, respectively. This highlights a notably superior gas-sensitive performance of the Fe3GeTe2/In2Se3 heterostructure compared to the Fe3GeTe2 monolayer gas devices. These findings provide valuable references for the application of multiferroic heterostructures in the field of gas sensors.

Abundant interfacial and intrinsic oxygen vacancies enabling small nickel/ceria nanocrystal efficient CO2 methanation

Smaller nano-sizes typically result in supported catalysts with abundant interfacial and intrinsic oxygen vacancies for better adsorption and activation of small molecules, including CO2, leading to improved efficiency of CO2 methanation. Here, Ni/CeO2-S with the smaller nano-size of around 4.2 nm is used to catalyze CO2 methanation, which exhibits significantly enhanced activity compared to larger nano-sized Ni/CeO2-L catalyst, even surpassing the most majority of previously reported catalysts using CeO2 as the support or Ni as the active metal. The coexistence of interfacial defects and intrinsic oxygen vacancies allows for enhanced adsorption and activation of CO2 molecules as well as H spillover, resulting in such improved CO2 methanation. In-situ DRIFTS demonstrate a nearly sole Formate pathway on Ni/CeO2-S for efficient CO2 hydrogenation. This research provides valuable insights into the reaction mechanism over a small nanosize supported catalyst.

Single walled carbon nanotubes/ZnO nanowires heterostructure array for NO2 gas sensing at low ppm levels

A layer-by-layer ZnO nanowire (NW)-Single Walled Carbon Nanotube (CNT) hybrid gas sensor has been proposed for effective detection of NO2 gas under a low exposure limit of 5 ppm. The fabricated hybrid sensor displayed good sensor response (S %), good selectivity and fast response time towards the target gas. S % value of 36.4 % under 5 ppm NO2 level at 250 °C and good selectivity response towards different interfering gases like SO2, CO and H2 have been observed. Meanwhile, fast response time values of 44.08 s (response) and 62.11 s (recovery) were observed at 300 °C under 5 ppm NO2 level. The sensor baseline resistance of the hybrid heterostructure (HS) was also found to be lower when compared to that of a bare ZnO NW sensor. In addition, the presence of Single Walled CNT in the HS was also shown to reduce the operational temperature of the sensor. Temperature played a significant role by controlling the adsorption and desorption kinetics of gas molecules on the surface. Moreover, the formation of p-n interface between Single Walled CNT (p-type) and ZnO NW (n-type) might have modulated the potential charge barrier on interacting with the adsorbed gases which inturn might have impacted the response of the hybrid sensor. In addition, the large surface areas offered by both NWs and nanotubes might have improved the gas adsorption capability thereby enhancing the overall hybrid sensor’s response.

Valence electron matching law for MXene-based single-atom catalysts

Single-atom catalysts (SACs) have attracted considerable interest in the fields of energy and environmental science due to their adjustable catalytic activity. In this study, we investigated the matching of valence electron numbers between single atoms and adsorbed intermediates (O, N, C, and H) in MXene-anchored SACs (M-Ti2C/M-Ti2CO2). The density functional theory results demonstrated that the sum of the valence electron number (VM) of the interface-doped metal and the valence electron number (VA) of the adsorbed intermediates in M-Ti2C followed the 10-valence electron matching law. Furthermore, based on the 10-valence electron matching law, we deduced that the sum of the valence electron number (k) and VM for the molecular adsorption intermediate interactions in M-Ti2CO2 adhered to the 11-valence electron matching law. Electrostatic repulsion between the interface electrons in M-Ti2CO2 and H2O weakened the adsorption of intermediates. Furthermore, we applied the 11-valence electron matching law to guide the design of catalysts for nitrogen reduction reaction, specifically for N2 → NNH conversion, in the M-Ti2CO2 structure. The sure independence screening and sparsifying operator algorithm was used to fit a simple three-dimensional descriptor of the adsorbate (R2 up to 0.970) for catalyst design. Our study introduced a valence electron matching principle between doped metals (single atoms) and adsorbed intermediates (atomic and molecular) for MXene-based catalysts, providing new insights into the design of high-performance SACs.

How does the integration of amino acids enhance the bonding ability of triazine-based inhibitors with iron surfaces: Insights from SCC-DFTB, COSMO-RS and molecular dynamics simulations

Theoretical investigations into the adsorption of molecules on metal surfaces play a pivotal role in the development of more efficient corrosion inhibitors. This study offers a novel approach by combining Density Functional Tight Binding (DFTB), Molecular Dynamics (MD) simulations, and conductor-like screening model for realistic solvation (COSMO-RS) calculations to comprehensively assess the interaction and diffusion properties of glycine (Gly), 2,2′-azanediyldiacetic acid (IDA), and 5-aminopentanoic acid (5-APA) with two 1,3,5-triazine (Tris) derivatives (Tris-Gly and Tris-IDA) for corrosion protection of carbon steel in acidic medium. The solvation properties of these molecules were evaluated alongside their interaction strength with the Fe(1 1 0) surface, considering both neutral and protonated forms. DFTB simulations revealed a clear trend in interaction energies, following the order: Tris-IDA > Tris-Gly > 5-APA > IDA > Gly. It ranges from −1.191 eV to −1.853 eV, with the highest stability observed for protonated Tris-IDA (−1.853 eV), while protonated Glycine exhibits the lowest interaction energy (−1.191 eV). These theoretical results diverged slightly from experimental observations, with Tris-Gly outperforming Tris-IDA, which was attributed to steric effects and solvent interactions. The DFTB results also indicated strong covalent interactions, particularly involving acetic groups, between the inhibitors’ orbitals and the iron’s 3d orbitals. MD simulations further demonstrated the impact of protonation on inhibitor mobility, with reduced diffusion coefficients due to enhanced electrostatic interactions and hydrogen bonding. COSMO-RS solvation analysis confirmed the strong hydrogen bonding capabilities of these molecules with water. Overall, this study elucidates the mechanisms of corrosion inhibition by integrating multiple simulation techniques, providing key molecular insights that can guide the design of more effective corrosion inhibitors. The findings emphasize the significance of electronic interactions and molecular structure in enhancing inhibitor performance, making this a valuable contribution to corrosion science.

Spin state regulated by asymmetric orbital hybridization in Ni-Fe2O3 to promote fenton-like catalytic activity

The manipulation of spin states in metal active sites can significantly impact the energetics of peroxymonosulfate (PMS) molecule adsorption and bond dissociation, thereby exerting influence on the reaction pathway and kinetics. However, the optimization of Fe2O3 catalysts for PMS activation has overlooked spin-related electron transfer and orbital interactions. In this study, we propose a Ni-doping strategy to modify the spin state of Fe2O3 (Ni-Fe2O3) through asymmetrical orbital hybridization (Ni-O-Fe) to enhance PMS activation, with the aim of establishing a correlation between spin state and catalytic activity. The high-spin Ni-Fe2O3/PMS system exhibits a significantly higher reaction rate constant (0.20 min−1), approximately 2.85 times greater than that observed in the low-spin Fe2O3/PMS system (0.07 min−1). The asymmetrical orbital coupling induced by Ni doping enhances spin splitting and electron delocalization within the Ni-Fe2O3 catalyst, creating an efficient electron transfer channel between the high-spin catalyst and adsorbed PMS molecules. This enhanced electron transfer disrupts charge distribution in PMS and elongates OO bonds, leading to a significant enhancement in OH generation potential. The establishment of a correlation between high spin active sites and PMS activation provides valuable insights into the intelligent design of spin-regulated nanocomposites for advanced water purification.

Highly sensitive and low-temperature triethylamine sensor based on in situ growth of hierarchical α-MoO3 flowers

To challenge high working temperature of present triethylamine (TEA) sensor, well-defined hierarchical α-MoO3 flowers were in situ grown on Al2O3 tubes through a simple solvothermal method. The α-MoO3 flowers were about 3 μm in diameter consisted of overlapping nanosheets with average thickness of ∼30 nm, growing radially from the center of the flowers. The α-MoO3 flowers in situ grew on Al2O3 tubes to constitute the thin film sensors, which exhibited improved gas-sensing performance to TEA compared to the thick film sensors painted with the powder of α-MoO3 produced in the same reaction system. The average response value of the α-MoO3 thin film sensors to 10 ppm TEA was 243.5 at relatively low operating temperature of 133 °C, which was 4.5 times as high as that of the thick film sensors (54.2). And the detection limit of the thin film sensors to TEA is further decreased to 0.001 ppm compared to the α-MoO3 thick film ones. The superior TEA-sensing capability should be attributed to the hierarchical nanostructure grown in situ that supplies more active sites for gas molecule adsorption and electron transfer. The synthesized α-MoO3 flowers with hierarchical nanostructure are promising material for trace TEA detection in practical application.

A Bacterial Capturing, Neural Network-Like Carbon Nanotubes/Prussian Blue/Puerarin Nanocomposite for Microwave Treatment of Staphylococcus Aureus-Infected Osteomyelitis.

Staphylococcus aureus (S. aureus)-infected osteomyelitis is a deep tissue infection that cannot be effectively treated with antibiotics. Microwave (MW) thermal therapy (MTT) and MW dynamic therapy (MDT) based on MW-responsive materials are promising for the therapy of bacteria-infected osteomyelitis occurring in deep tissues that cannot be effectively treated with antibiotics. In this work, the MW-responsive system of carbon nanotubes (CNTs)/Prussian blue (PB)/puerarin (Pue) with stable network-like structures is constructed. The PB is grown in situ on the CNTs, and its introduction not only reduces the aggregation of the network-like structures of the CNTs, but the large specific surface area and mesoporous structure can also provide many active sites for the adsorption of oxygen and polar molecules. Pue is a natural anti-inflammatory material that reduces inflammation at the infection site. The composite of the CNTs and PB avoids the skin effect and thus can improve dielectric and reflection losses. The MW thermal response of CNTs/PB/Pue is mainly due to the occurrence of reflection loss, dielectric loss, multiple reflections and scattering, interface polarization, and dipole polarization. In addition, under MW irradiation, the CNTs/PB/Pue can produce reactive oxygen species (ROS), such as singlet oxygen (1O2), hydroxyl radical (·OH).

Molecular Reconfiguration of Disordered Tellurium Oxide Transistors with Biomimetic Spectral Selectivity.

Reconfigurable devices with field-effect transistor features and neuromorphic behaviors are promising for enhancing data processing capability and reducing power consumption in next-generation semiconductor platforms. However, commonly used 2D materials for reconfigurable devices require additional modulation terminals and suffer from complex and stringent operating rules to obtain specific functionalities. Here, a p-type disordered tellurium oxide is introduced that realizes dual-mode reconfigurability as a logic transistor and a neuromorphic device. Due to the disordered film surface, the enhanced adsorption of oxygen molecules and laser-induced desorption concurrently regulate the carrier concentration in the channel. The device exhibits high-performance p-type characteristics with a field-effect hole mobility of 10.02 cm2 V-1 s-1 and an Ion/Ioff ratio exceeding 106 in the transistor mode. As a neuromorphic device, the vision system exhibits biomimetic bee vision, explicitly responding to the blue-to-ultraviolet light. Finally, in-sensor denoising and invisible image recognition in static and dynamic scenarios are achieved.

Surface acoustic wave platform integrated with ultraviolet activated rGO-SnS2 nanocomposites to achieve ppb-level dimethyl methylphosphonate detection at room-temperature

Dimethyl methylphosphonate (DMMP) is commonly used as an alternative for demonstrating to detect sarin, which is one of the most toxic but odorless chemical nerve agents. Among various types of DMMP sensors, those utilizing surface acoustic wave (SAW) technology provide notable advantages such as wireless/passive monitoring, digital output, and a compact, portable design. However, key challenges for SAW-based DMMP sensors operated at room temperature lies in simultaneous enhancement of sensitivities and reduction of detection limits. In this study, we developed a binary material strategy by combining reduced graphene oxide (rGO) and tin disulfide (SnS2) with (100)-facets orientation as sensing layers of SAW device for DMMP detection utilized at room temperature. Ultraviolet (UV) light was applied to activate the sensitive film and reduce the sensor's response time. The developed SAW DMMP sensor demonstrated a superior sensitivity (−1298.82 Hz/ppm), a low detection limit of 50 ppb, and a hysteresis below 1.5%, along with fast response/recovery time (39.2 s/28.4 s), excellent selectivity, long-term stability and repeatability. The formation of shrub-like rGO-SnS2 heterojunctions with abundant surface defects and large specific surface areas, high-energy (100) crystalline surfaces of SnS2, and photogenerated carriers generated by UV irradiation were pinpointed as the crucial sensing mechanisms. These factors collectively enhanced adsorption and reaction dynamics of DMMP molecules.

Effect of gas type on properties of anionic surfactant foam system

The foam drainage technique is considered to be a promising measure for solving the problem of liquid accumulation in natural gas wells and gathering pipelines. However, differences in gases can greatly affect the performance of surfactant foam, thus limiting the application of this technology. To elucidate the mechanism of natural gas components influencing foam properties, the interfacial properties of hydrocarbon gas-surfactant-water system were analyzed thermodynamically and kinetically by combining molecular dynamics simulations and foaming experiments. The results show that with the increasing alkane chain length, the foaming volume and half-life of the foam are gradually rising, while the gas–liquid interfacial tension is decreasing, which is consistent with the results of molecular dynamics simulations. Compared with air, hydrocarbon gases are more beneficial for foam generation and stabilization. The interfacial adsorption of alkane molecules and the interaction between alkanes and surfactants are the main factors affecting the interfacial tension and film stability of different systems.

Adsorption grand potential of OH on metal oxide surfaces.

Describing chemical processes at solid-liquid interfaces as a function of a fixed electron chemical potential presents a challenge for electronic structure calculations and is essential for understanding electrochemical phenomena. Grand Canonical Density Functional Theory (GCDFT) allows treating solid-liquid interfaces in such a way that studying the influence of a fixed electron potential arises naturally. In this work, GCDFT is used to compute the adsorption grand potential (AGP), a key parameter for understanding and predicting the behavior of adsorbates on surfaces. We focused on the adsorption of an OH molecule on three metallic surfaces commonly used in electrochemical processes, such as the oxygen evolution reaction (OER). Our study aims to offer insights into how AGP can be used to compare adsorption strengths under different fixed electron chemical potentials, which is crucial for designing efficient electrode materials. By determining the average number of electrons self-consistently under varying chemical potentials, we showed how one can distinguish between electron acquisition and depletion during the adsorption process, offering a deeper understanding of the adsorbate-surface interactions. The approach used in this work employs the Kohn-Sham-Mermin formulation of the Grand Canonical Density Functional Theory. The computations were performed using the periodic open-source density functional theory software, JDFTx, with the Garrity-Bennett-Rabe-Vanderbilt library of ultrasoft pseudopotentials. Calculations were made using truncated Coulomb potentials and the auxiliary Hamiltonian method with the PBE exchange-correlation functional, along with DFT-D2 long-range dispersion corrections. The implicit solvation model CANDLE was used to describe the electrolyte with a 1M concentration.

Assay for Characterizing Adsorption-Properties of Surfaces (APS).

Analytes, from sample preparation, until entering an analytical instrument, are prone to adsorb to surfaces, driven by the chemical properties of the surface and the liquids they are dissolved in. This problem can be addressed with internal standards when a single or few known analytes are quantified that are usually not available in omics. However, minimal to no loss of analytes is the aim. Here, we present a novel assay for qualifying and quantifying interactions responsible for adsorption of molecules to surfaces (APS) by using LC-MS/MS-based differential quantitative analysis. To reflect a broad range of chemical interactions with surfaces, a reference mixture of thousands of tryptic peptides, with known compositions was selected, representing a variety of different chemical characteristics. The assay was tested by investigating the adsorption properties of several different vials with different surface chemistries. A significant number of hydrophobic peptides adsorbed to conventional polypropylene vials. In contrast, only few peptides adsorbed to polypropylene vials, assigned as low-protein-binding. The highest number of peptides adsorbed to glass vials driven by electrostatic interactions. In summary, the new assay is suitable to characterize adsorption properties of different surfaces and to approximate the loss of analytes during sample preparation.

Label-Free Single-Molecule Electrical Sensor for Ultrasensitive and Selective Detection of Iodide Ions in Human Urine.

Herein, a label-free single-molecule electrical sensor was first proposed for the ultrasensitive and selective detection of iodide ions in human urine. Single-molecule conductance measurements in different halogen ion solutions via scanning tunneling microscopy break junction (STM-BJ) clearly revealed that I- ions strongly affect the stability and displacement distance (Δz) distribution of molecular junctions. Theoretical calculations prove that the specific adsorption of I- ions modifies the surface properties and weakens the molecular adsorption. Furthermore, the average conductance peak area versus the logarithm of the I- ion concentration has a very good linear relationship in the range of 5 × 10-6 to 5 × 10-10 M, with a correlation coefficient of 0.99. This quantitative analysis remains valid in the presence of interfering ions of SO42-, ClO4-, Br-, and Cl- as well as interfering molecules of ascorbic acid, uric acid, dopamine, and cysteine. A cross-comparison of the human urine detection results of this single-molecule electrical sensor with those of the clinical method of As3+-Ce4+ catalytic spectrophotometry revealed an average difference of 0.9%, which decreased the detection time of 2 h with the traditional method to approximately 15 min. This work proves the promising practical potential of the single-molecule electrical technique for relevant clinical analysis.