Single Nanochannel Research Articles

Sensing creatinine in urine via the iontronic response of enzymatic single solid-state nanochannels

Sensing creatinine in urine via the iontronic response of enzymatic single solid-state nanochannels

Photo responsive single layer MoS2 nanochannel membranes for photocatalytic degradation of contaminants in water

The major polluting aspects of our global fashion industries are the textile wastewater that turns black all our freshwater reservoirs. Nano-filtration through membrane technology is one of the biggest solutions of industrial wastewater treatment but the fouling of membrane is the major limitation of previous work. In this research, novel PVDF/MoS2-TNT (PMT) nanocomposite membranes were fabricated through a modified In-situ polymerisation phase inversion method. X-ray diffraction (XRD) analysis also confirmed the β-phase of PVDF within the developed PVDF/MoS2-TNT membrane. XPS analysis provides evidence about the presence of a specific chemical states of titanium nanotube and molybdenum disulphide which is involved in the photocatalytic degradation of pollutant molecules. Scanning electron microscope (SEM) shows that our membranes are porous in nature. PVDF/MoS2-TNT membranes exhibit excellent filtration efficiency (∼97%) for textile wastewater. The results and outcomes of the research demonstrate that PMT membranes have enormous potential in the commercial application of textile wastewater treatment.

Nanofluidic Detection Platform for Simultaneous Light Absorption and Scattering Measurement of Individual Nanoparticles in Flow.

Characterization and quantification of plasmonic nanoparticles at the single particle level have become increasingly important with the advancements in nanotechnology and their application to various biological analyses including diagnostics, photothermal therapy, and immunoassays. While various nanoparticle detection methodologies have been developed and widely used, simultaneous measurement of light absorption and scattering from individual plasmonic nanoparticles in flow is still challenging. Herein, we describe a novel nanofluidic detection platform that enables simultaneous measurement of absorption and scattering signals from individual nanoparticles within a nanochannel. Our detection platform utilized optical diffraction phenomena by a single nanochannel as both a readout signal for photothermal detection and a reference light for interferometric scattering detection. Through the elucidation of the frequency effect on the detection performance and optimization of experimental conditions, we achieved the classification of gold and silver nanoparticles with a diameter of 20-60 nm at an average accuracy score of 82.6 ± 2.1% by measured data sets of absorption and scattering signals. Furthermore, we demonstrated the concentration determination of plasmonic nanoparticle mixtures using a trained Support vector machine (SVM) classifier. Our simple yet sensitive nanofluidic detection platform will be a valuable tool for the analysis of nanoparticles and their applications to chemical and biological assays.

The role of ionic concentration polarization on the behavior of nanofluidic membranes

Water, the elixir of life, faces a pressing challenge—salinity. As humanity's demand for freshwater intensifies, the significance of efficient desalination processes becomes paramount. The promising prospects of nanofluidic membranes and unique electrokinetic phenomena like ion concentration polarization (ICP) signal optimistic strides in enhancing salt removal processes. This study is dedicated to elucidating the transport mechanism of buffer ions at interfaces between micro and nanochannels. To achieve this, we introduce a multiphysics coupling model that incorporates a boundary condition for the fixed surface voltage, offering a comprehensive description of the impact of nanochannel arrays. In this context, it is important to note that the nanochannel array is characterized by a positive charge density, akin to a cation exchange membrane (CEM), seamlessly integrated into the microchannel wall to serve as a cationic half-cell. The analysis involved solving governing equations, including the Poisson-Nernst-Planck, continuity, and Navier-Stokes equations, numerically using the finite element method in an unsteady state. Employing cylindrical nanochannel array configurations—single, dual, and triple—we scrutinized their impact on salt species concentration and removal efficiency under specified conditions (c0=1mM, ρv=2C/m3, LN=10μm, VT=26mV, Vsurr=4VT, VL/VR=8,t≥0.5 and ζ=−60mV). The single nanochannel array configuration demonstrated a relatively uniform salt distribution, achieving a removal efficiency of approximately 58%. The introduction of two nanochannel arrays at distinct locations resulted in a notable increase in removal efficiency, reaching 72%, particularly in the "down first" configuration, emphasizing a synergistic effect. The presence of three nanochannel arrays, each with varying lengths, produced intricate patterns, with the highest removal efficiency observed at 91% in the "different length" condition. This study emphasizes the superior desalination capabilities achievable through multiple nanochannel arrays, advancing our understanding of nanofluidic membrane applications for efficient water desalination. In conclusion, emulating electrodialysis membrane procedures, particularly by integrating an anionic half-cell, holds promise for further advancing desalination processes, offering a potential avenue to enhance efficiency.

Advances in Two-Dimensional Ion-Selective Membranes: Bridging Nanoscale Insights to Industrial-Scale Salinity Gradient Energy Harvesting.

Salinity gradient energy, often referred to as the Gibbs free energy difference between saltwater and freshwater, is recognized as "blue energy" due to its inherent cleanliness, renewability, and continuous availability. Reverse electrodialysis (RED), relying on ion-selective membranes, stands as one of the most prevalent and promising methods for harnessing salinity gradient energy to generate electricity. Nevertheless, conventional RED membranes face challenges such as insufficient ion selectivity and transport rates and the difficulty of achieving the minimum commercial energy density threshold of 5 W/m2. In contrast, two-dimensional nanostructured materials, featuring nanoscale channels and abundant functional groups, offer a breakthrough by facilitating rapid ion transport and heightened selectivity. This comprehensive review delves into the mechanisms of osmotic power generation within a single nanopore and nanochannel, exploring optimal nanopore dimensions and nanochannel lengths. We subsequently examine the current landscape of power generation using two-dimensional nanostructured materials in laboratory-scale settings across various test areas. Furthermore, we address the notable decline in power density observed as test areas expand and propose essential criteria for the industrialization of two-dimensional ion-selective membranes. The review concludes with a forward-looking perspective, outlining future research directions, including scalable membrane fabrication, enhanced environmental adaptability, and integration into multiple industries. This review aims to bridge the gap between previous laboratory-scale investigations of two-dimensional ion-selective membranes in salinity gradient energy conversion and their potential large-scale industrial applications.

Pore-Size-Dependent Role of Functional Elements at the Outer Surface and Inner Wall in Single-Nanochannel Biosensors.

Biological nanopores feature functional elements on the outer surfaces (FEOS) and inner walls (FEIW), enabling precise control over ions and molecules with exceptional sensitivity and specificity. This provides valuable inspiration to scientists for the development of intelligent artificial nanochannel-based platforms, with a wide range of potential applications, including biosensors. Much effort has been dedicated to investigating the distinct contribution of FEOS and FEIW of multichannel membrane biosensors. However, the intricate interactions among neighboring pores in multichannel biosensors have presented challenges. This underscores the untapped potential of single nanochannels as ideal candidates in this field. Here, we employed single nanochannel membranes with different pore sizes to investigate the distinct contributions of FEIW and FEOS to single-nanochannel biosensors, combined with numerical simulations. Our findings revealed that alterations in the negative charges of FEIW and FEOS, induced by target binding, have differential effects on ion transport, contingent upon the degree of nanoconfinement. In the case of smaller pores, such as 20 nm, the ion concentration polarization driven by FEIW can independently control ion transport through the surface's electric double layer. However, as the pore size increases to 40-60 nm, both FEIW and FEOS become essential for effective ion concentration polarization. When the pore size reaches 100 nm, both FEIW and FEOS are ineffective and thus unsuitable for biosensors. Simulations demonstrate that the observed phenomena can be attributed to the interactions between the charges of FEIW and FEOS within the overlapping electric double layer under confinement. These results underscore the critical role of pore size as a key parameter in governing the functionality of probes within or on nanopore-based biosensors as well as in the design of nanopore-based devices.

Ion Transport in Multi-Nanochannels Regulated by pH and Ion Concentration.

Nanochannels are a powerful technique for detecting a wide range of biomolecules without labeling. The ion transport phenomena in nanochannel arrays differ from those in single nanochannels and are caused by interchannel communication. This study uses a fully coupled Poisson-Nernst-Planck (PNP) and Navier-Stokes model to investigate ion transport in nanochannel arrays. Instead of being set at a constant value, the surface charge density used in this study is established by the protonation and deprotonation of the silanol groups that are present on the walls of the silicon-based nanochannels. The surface charge density of the nanochannel walls varies with the number of nanochannels, the channel lateral distance, and the background solution properties, which consequently influence the ionic concentration distribution, flow velocity, and electric field strength. For example, in different numbers of nanochannel systems, the ion concentration in nanochannels is not much different, but it is different in reservoirs, especially near the openings of nanochannels. The number of nanochannels and the distance between nanochannels can also affect the formation of electro-convective vortex zones under certain conditions. These findings can aid in optimizing the nanochannel array design by regulating the number and distance of nanochannels and facilitating the construction of solid-state nanochannel arrays with any desired nanochannel dimensions.

A Simple Cost-Effective Method to Fabricate Single Nanochannels by Embedding Electrospun Polyethylene Oxide Nanofibers.

Solid state nanochannels provide significant practical advantages in many fields due to their interesting properties, such as controllable shape and size, robustness, ion selectivity. But their complex preparation processes severely limit their application. In this study, a simple cost-effective method to fabricate single nanochannel by embedding a single polyethylene oxide (PEO) nanofiber is presented. Firstly, PEO nanofibers are prepared by electrospinning, and then a single PEO nanofiber are precisely transferred to the target sample using a micromanipulation platform. Then, PDMS is used for embedding, and finally, the PEO nanofiber is dissolved to obtain a single nanochannel. Unlike other methods of preparing nanochannels by embedding nanofibers, this method can prepare single nanochannel. The diameter of nanochannel can be as fine as 100 nm, and the length can reach several micrometers. The power generation between two potassium chloride solutions with various combinations of concentrations was investigated using the nanochannel. This low-cost flexible nanochannel can also be used in various applications, including DNA sequencing and biomimetic ion channel.

Nanoprecipitation-Enhanced Sensitivity in Enzymatic Nanofluidic Biosensors.

Single nanochannels show unique transport properties due to nanoconfinement. It has been demonstrated that at submillimolar concentrations of divalent cations, a nanoprecipitation reaction can occur in nanochannels. Although several reports have shown, described, and modeled the nanoprecipitation process, no further advantages have been taken from this phenomenon. Here, we show that the nanoprecipitation reaction can be incorporated into enzyme-modified nanochannels to enhance the performance of small-molecule biosensors via in situ amplification reactions. Contrary to the working principle of previous enzymatic nanofluidic biosensors, the nanofluidic biosensor described in this work operates on the basis of concerted functions: pH-shifting enzymatic activity and nanoprecipitation. We show that the simple addition of Ca2+ and Mg2+ ions in the working analyte solution containing urea can lower the detection limit from the nanometer to the subnanometer regime and modulate the dynamic linear range. This approach enables the implementation of more sensitive real-time nanofluidic detection methods without increasing the complexity of the nanofluidic platform or the sensing approach. We envision that the integration of concerted functions in nanofluidic architectures will play a key role in expanding the use of these nanoscale devices for analytical purposes.

Highly Sensitive Acetylcholine Biosensing Via Chemical Amplification of Enzymatic Processes in Single Track-Etched Nanochannels

Neurotransmitters are endogenous chemical messengers that play crucial roles in the transmission, enhancement and conversion of specific signals between neurons and other cells and are considered biomarkers of neurodegenerative diseases.[1] Neurodegenerative diseases cause progressive loss of cognitive and/or motor function and, as life expectancy rises, they imply major challenges for societies with rapidly aging populations.[2] As a result, monitoring neurotransmitters is becoming increasingly relevant in clinical environments. Acetylcholine (Ach) is a neurotransmitter that plays a key role in the communication between neurons in the spinal cord and nerve skeletal junctions in vertebrates. [3] Since an abnormal concentration of Ach has proven to be related to neurodegenerative diseases, novel strategies for highly sensitive and specific Ach (bio)sensing are in great demand.In this work we present the construction of Ach enzymatic biosensors with remarkable sensitivity by acetylcholinesterase immobilization on polyamine-modified single nanochannels via electrostatic self-assembly. [4] To fabricate bullet-shaped single nanochannels in polyethylene terephthalate (PET), 12 µm thick PET foils are irradiated with a single swift heavy ion. The resulting ion track consists of highly localized damaged material along the ion trajectory and is selectively dissolved in a highly basic aqueous solution under asymmetric conditions to obtain a bullet-shaped channel. The controlled PET hydrolysis exposes carboxylic groups at the channel surface (negative charge at pH < 4), which allows the immobilization of further functional groups to design and construct the biosensor.Here, we will discuss in detail the sensor design, the applied functionalization strategy, and the performance of the sensor. In short, changes in the surface charge of the nanochannel lead to measurable changes in the transmembrane current in a steady-state configuration. We will show experimental results that evidence that the designed sensor successfully transduces the presence of acetylcholine into measurable ionic signals with a 16 nM low limit of detection.[1] World Health Organization, Neurological Disorders: Public Health Challenges, World Health Organization Press, Geneva, Switzerland,2007.[2] L. Gan, M. R. Cookson, L. Petrucelli and A. R. La Spada,Nat. Neurosci., 2018, 21, 1300–1309.[3] M. Hasanzadeh, N. Shadjou and M. de la Guardia, TrAC, Trends Anal. Chem., 2017, 86, 107–121.[4] Yamili Toum Terrones, Gregorio Laucirica, Vanina M. Cayón, Gonzalo E. Fenoy, M. Lorena Cortez, María Eugenia Toimil-Molares, Christina Trautmann, Waldemar A. Mamisollé and Omar Azzaroni, Chem. Commun., 2022, 58, 10166

Biosensing with Tailored Track-Etched Nanochannels

Inspired by the high sensitivity, efficiency and selectivity of biological ion channels, the development of solid-state nanochannel sensors has been at the forefront of nanotechnology research in the last years. Many researchers worldwide have concentrated their efforts on the development of artificial nanochannels that can mimic the features of biological ion channels. These synthetic nanostructures are based on abiotic materials which provide higher robustness, thermal stability, chemical versatility and mechanical resistance than their biological counterparts. Furthermore, synthetic nanochannels and specific surface functionalization strategies have enabled fine control over the geometry and charge distribution which yielded the ability to manipulate the flux of ions through the channel. This gave rise to the formation of nanochannel-based platforms with applications in (bio)sensing as well as other fields. The development of chemical- and biosensors requires a combination of reliable nanofabrication techniques and versatile surface modification strategies, which render high sensitivity and high selectivity, respectively [1].Tailored single polymer nanochannels are routinely fabricated by ion-track nanotechnology. Polymer films are first irradiated with individual swift heavy ions at the GSI UNILAC accelerator. Each ion generates a highly localized cylindrical damage zone along its trajectory. These so-called ion tracks are subsequently dissolved and enlarged in a chemical etching process. By selecting suitable etching conditions, geometry (cylindrical, conical or bullet-like) and size of the nanochannels can be adjusted. The nanochannel surface can then be functionalized by means of different chemical strategies to enhance the sensing capabilities.There are two main nanochannel sensing techniques, ion current rectification (ICR) and resistive-pulse sensing (RPS). Both are affected by the geometry and surface charge of the nanochannel and based on measuring the change in ion current flowing through the channel induced by the chosen analyte [2]. In both approaches, the presence of a target analyte triggers a variation in the physicochemical properties of the channel which can be related to measurable changes in the transmembrane current, and is proportional to the analyte concentration.In this contribution, we will present nanochannel sensing platforms based on several single polymer channels fabricated by ion-track nanotechnology and a selection of surface functionalization strategies applied to the nanochannels. We will then discuss selected examples recently obtained with these tailored functionalized nanochannels and demonstrate selective and sensitive sensing applications based on both the ICR and RPS phenomena.[1] Toum Terrones, Y., Cayón, V. M., Laucirica, G., Cortez, M. L., Toimil-Molares, M. E., Trautmann, C., ... & Azzaroni, O. (2022). Ion Track-Based Nanofluidic Biosensors. In Miniaturized Biosensing Devices: Fabrication and Applications (pp. 57-81). Singapore: Springer Nature Singapore.[2] Kaya, D., & Keçeci, K. (2020). Track-etched nanoporous polymer membranes as sensors: A review. Journal of The Electrochemical Society, 167(3), 037543.

Single-Nanoparticle-Based Nanomachining for Fabrication of a Uniform Nanochannel Sensor.

The structure of nanomaterials and nanodevices determines their functionality and applications. A single uniform nanochannel with a high aspect ratio is an attractive structure due to its unique rigid structures, easy preparation, and diverse pore structures and it holds significant promising importance in fields such as nanopore sensing and nanomanufacturing. Although the metal-nanoparticle-assistant silicon etching technique can produce uniform nanochannels, however, the fabrication of single through nanochannels remains a challenge thus far. A simple and versatile strategy is developed that allows for the retention of individual gold nanoparticle on a substrate, enabling single-nanoparticle nanomachining. This method involves three steps: the formation of a carbon protective layer on individual nanoparticles via electron-beam irradiation, selective removal of unprotected nanoparticles using a corrosive agent, and subsequent elimination of the carbon layer. This enables the fabrication of a single submillimeter-long uniform through nanochannel in the silicon wafer, which can be employed for nanopore sensing and shape-based nanoparticle distinguishing. The developed method can also facilitate single-nanoparticle studies and nanomachining for a broad application in materials science, electronics, micro/nano-optics, and catalysis.

Enhancing 4-aminophenol detection using bismuth ferrite nanoparticles in functional nanochannels

This work presents a simple and rapid electrochemical method employing a conical nanochannel modified with bismuth ferrite (BFO) nanoparticles for the direct determination of 4-aminophenol (4-AP), a commonly used drug intermediate in pharmaceutical preparations. The phase pure BFO nanoparticles were synthesized by the coprecipitation technique. Subsequently, we created the single conical nanochannels within polyethylene terephthalate (PET) membranes using the asymmetric track-etching method. To facilitate the immobilization of BFO nanoparticles onto the nanochannel's surface, we initially functionalized it with poly (allylamine hydrochloride) (PAH). The BFO-modified single conical nanochannel obtained was utilized for sensing 4-AP, demonstrating significantly improved sensitivity within a linear dynamic response range from 400 μM to 1 mM, as compared to both unmodified and PAH-modified channels. To gain further insights into the interaction between BFO and 4-AP, we employed cyclic voltammetry and differential pulse voltammetry techniques. Our in-depth analysis, based on scan rate voltammograms, revealed that the interaction mechanism primarily involved the adsorption phenomenon between BFO nanoparticles and 4-AP. This enhancement in sensitivity, as corroborated by the electrochemical techniques, underscores the efficacy of the BFO-modified nanochannel for 4-AP detection. Robust conical nanochannels functionalized with nanoparticles, show promise in developing highly selective, cost-effective, and portable biosensors.

Highly sensitive and low-cost detecting and recovering Ce3+ from ammonia nitrogen wastewater using bio-inspired nanochannel/membrane

The increasing demand for monitoring and recovering rare earth elements (REE) has driven the development of new strategies for detection and enrichment of lanthanide metal ions. In this study, we were inspired from ligand-responsive ion channels in cell membrane to construct artificial single nanochannels and multipore membranes for achieving for the first time ultra-sensitive detection and environmentally friendly recovery of Ce3+ from ammonia nitrogen wastewater which is the most common wastewater. A single conical nanochannel with polyelectrolyte functionalization was developed, wherein polyacrylic acid (PAA) played a crucial role by providing affinity carboxyl groups that form complexes with Ce3+. This interaction led to a measurable change in the ion rectification factor within the asymmetric nanochannel, enabling the ultra-sensitive detection of Ce3+. Under optimized experimental conditions, the rectification factor exhibited a proportional relationship with the logarithm of Ce3+ concentration, covering linear ranges of 1 nM − 1 × 103 nM and 1 μM − 500 μM, with a detection limit of 1 nM. To evaluate the applicability of this method for real sample analysis, the Ce3+ content in ammonia nitrogen water samples was determined. The results demonstrated the excellent performance of the proposed method for detecting Ce3+ with the minimum recovery percentage of 95.0 %. The theoretical calculations further confirmed that PAA exhibits the highest binding energy with Ce3+, reinforcing its importance in the detection process. Additionally, multipore membranes were designed based on the same principle for the recovery of Ce3+ from ammonia nitrogen wastewater. Impressively, the recovery rate reached 91.97%. Considering the similarity among REEs, the recyclable detection method presented in this study can not only monitor and recovery Ce3+ but also holds great significance for all REEs detection and resource reuse.

Nanofluidic Device for Detection of Lysine Methylpeptides and Sensing of Lysine Methylation

Protein methylation is the smallest possible yet vitally important post-translational modification (PTM). This small and chemically inert addition in proteins makes the analysis of methylation more challenging, thus calling for an efficient tool for the sake of recognition and detection. Herein, we present a nanofluidic electric sensing device based on a functionalized nanochannel that was constructed by introducing monotriazole-containing p-sulfonatocalix[4]arene (TSC) into a single asymmetric polymeric nanochannel via click chemistry. The device can selectively detect lysine methylpeptides with subpicomole sensitivity, distinguish between different lysine methylation states, and monitor the lysine methylation process by methyltransferase at the peptide level in real time. The introduced TSC molecule, with its confined asymmetric configuration, presents the remarkable ability to selectively bind to lysine methylpeptides, which, coupled with the release of the complexed Cu ions, allows the device to transform the molecular-level recognition to the discernible change in ionic current of the nanofluidic electric device, thus enabling detection. This work could serve as a stepping stone to the development of a new methyltransferase assay and the chemical that specifically targets lysine methylation in PTM proteomics.

The Enhancing Ionic Current Rectification in Single Graphene Conical Nanochannel

Enhanced ionic current rectification induced by the concentration gradient has been reported recently owing to the development of asymmetric nanofluidic system, in particular graphene nanochannels. However, the reasons for the enhancement of ionic current rectification of graphene conical nanochannels are not well understood. Herein, a finite element model of a single graphene conical nanochannel is established to explore the fundamental mechanisms of the ionic current rectification. The model proves that the highest cation concentration caused by graphene is almost 42 times higher than the bulk ion concentration. Compared with the nongraphene model, the graphene with higher surface charge density can absorb more cation in the tip (the small pore) of graphene conical nanochannel. Besides, the nanoscale corner consisting of graphene membrane and the wall of the conical nanochannel is a semihermetic reservoir for cation accumulation. It demonstrates that the enhancement of ionic current rectification is mainly ascribed to the unique structure of the graphene nanochannel and the graphene membrane with a high surface charge density. This work provides a new mechanism explanation about the influence of graphene in ionic current rectification.

Light-Driven Ion Transport through Single-Heterojunction Nanopores.

Inspired by natural photosynthesis, light has become an emerging ionic behavior regulator and ion-pumping source. Nanoprocessing technology has allowed the bridge between the light-regulated nanofluids and the optoelectronic properties of two-dimensional (2D) materials, which inspires applications like energy harvesting and enhances fundamental understandings in nanofluidics. However, unlike light-induced ion pumping based on densely layered membranes with multiple nanochannels, experimental implementation on atomically thin materials featuring only a single nanochannel remains challenging. Here, we report light-induced ion pumping based on a single artificial heterojunction nanopore. Under light illumination, the induced current through a single nanopore reaches tens of picoamperes. The hole-electron separation originating from the optoelectrical property of a van der Waals PN junction is proposed to capture the light-driven ion transport. Further, different methods are adopted to modify the ion behavior and response time, presenting potential applications in fluidic photoenergy harvesting, photoelectric ion transport control, and bionic artificial neurons.

Switchable Ion Current Saturation Regimes Enabled via Heterostructured Nanofluidic Devices Based on Metal-Organic Frameworks.

The use of track-etched membranes allows further fine-tuning of transport regimes and thus enables their use in (bio)sensing and energy-harvesting applications, among others. Recently, metal-organic frameworks (MOFs) have been combined with such membranes to further increase their potential. Herein, the creation of a single track-etched nanochannel modified with the UiO-66 MOF is proposed. By the interfacial growth method, UiO-66-confined synthesis fills the nanochannel completely and smoothly, yet its constructional porosity renders a heterostructure along the axial coordinate of the channel. The MOF heterostructure confers notorious changes in the transport regime of the nanofluidic device. In particular, the tortuosity provided by the micro- and mesostructure of UiO-66 added to its charged state leads to iontronic outputs characterized by an asymmetric ion current saturation for transmembrane voltages exceeding 0.3V. Remarkably, this behavior can be easily and reversibly modulated by changing the pH of the media and it can also be maintained for a wide range of KCl concentrations. In addition, it is found that the modified-nanochannel functionality cannot be explained by considering just the intrinsic microporosity of UiO-66, but rather the constructional porosity that arises during the MOF growth process plays a central and dominant role.

Smart Nano-switch with Flexible Modulation of Ion Transport Using Multiple Environmental Stimuli.

In this work, we demonstrate a unique nano-switch with triple environmental stimuli based on the action of functional copolymer brushes in a single conical nanochannel. This nanodevice flexibly and efficiently modulates ion transport properties under the influence of three environmental stimuli: light, pH and temperature. The triple factors can not only play a regulatory role independently, but their synergistic cooperation could fully activate the ionic gate and reversibly control the gating direction. In addition, the nano-switch can switch transport properties on demand in the face of complex combinations of different factors. This work promotes the development of intelligent bionic ion channels, which holds promise for biosensing, energy conversion and biomedical research.

Triazol-Methanaminium-Pillar[5]arene-Functionalized Single Nanochannel for Quantitative Analysis of Pyrophosphate in Water.

Inorganic pyrophosphate (PPi) is an important biological functional anion and plays crucial roles in life science, environmental science, medicine, and chemical process. Quantification of PPi in water has far-reaching significance for life exploration, disease diagnosis, and water pollution control. The label-free quantitative detection of PPi anions with a nanofluidic sensing device based on a conical single nanochannel is demonstrated. The channel surface is functionalized with a synthetic PPi receptor, triazol-methanaminium-functionalized pillar[5]arene (TAMAP5), using carbodiimide coupling chemistry. Due to the specific binding between TAMAP5 and PPi, the functionalized nanochannel can discriminate PPi from other inorganic anions with high selectivity through ionic current recording, even in the presence of various interfering anions. The current response exhibits a linear correlation with PPi concentration in the range from 1 × 10-7 to 1 × 10-4 M with a limit of detection of 6.8 × 10-7 M. A spike-and-recovery analysis of PPi in East Lake water samples indicates that the proposed nanofluidic sensor has the ability to quantitate micromolar concentrations of PPi in environmental water samples.