Conical Nanochannel Research Articles

Online detecting living cells released TNF-α and studying intercellular communication using SuperDNA self-assembled conical nanochannel

Online detecting living cells released TNF-α and studying intercellular communication using SuperDNA self-assembled conical nanochannel

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.

Ion Transport in Intelligent Nanochannels: A Comparative Analysis of the Role of Electric Field.

This research delves into investigating ion transport behavior within nanochannels, enhanced through modification with a negatively charged polyelectrolyte layer (PEL), aimed at achieving superior control. The study examines two types of electric fields─direct current and alternating current with square, sinusoidal, triangular, and sawtooth waveforms─to understand their impact on ion transport. Furthermore, the study compares symmetric (cylindrical) and asymmetric (conical) nanochannel geometries to assess the influence of overlapping electrical double layers (EDLs) in generating specific electrokinetic behaviors such as ionic current rectification (ICR) and ion selectivity. The research employs the finite element method to solve the coupled Poisson-Nernst-Planck and Navier-Stokes equations under unsteady-state conditions. By considering factors such as electrolyte concentration, soft layer charge density, and electric field type, the study evaluates ion transport performance in charged nanochannels, investigating effects on concentration polarization, electroosmotic flow (EOF), ion current, rectification, and ion selectivity. Notably, the study accounts for ion partitioning between the PEL and electrolyte to simulate real conditions. Findings reveal that conical nanochannels, due to improved EDL overlap, significantly enhance ion transport and related characteristics compared to cylindrical ones. For instance, under ηε = ηD = 0.8, ημ = 2, C0 = 20 mM, and NPEL/NA = 80 mol m-3 conditions, the average EOF for conical and cylindrical geometries is 0.1 and 0.008 m/s, respectively. Additionally, the study explores ion selectivity and rectification based on the electric field type, unveiling the potential of nanochannels as ion gates or diodes. In cylindrical nanochannels, the ICR remains at unity, with lower ion selectivity across waveforms compared to conical channels. Furthermore, rectification and ion selectivity trends are identified as Rf,square > Rf,DC > Rf,triangular > Rf,sinusoidal > Rf,sawtooth and Ssawtooth > Ssinusoidal > Striangular > SDC > Ssquare for conical nanochannels. Our study of ion transport control in nanochannels, guided by tailored electric fields and unique geometries, offers versatile applications in the field of Analytical Chemistry. This includes enhanced sample separation, controlled drug delivery, optimized pharmaceutical analysis, and the development of advanced biosensing technologies for precise chemical analysis and detection. These applications highlight the diverse analytical contributions of our methodology, providing innovative solutions to challenges in chemical analysis and biosensing.

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.

Electrokinetic ion rectification coupled with surface charge and thermal dependence in the conical nanochannel

With the further development of nanotechnology, electrokinetic ion rectification (ICR) is receiving increasing attention. Since the chemical equilibrium boundary is more suitable for expressing the wall charging characteristics and the coincidence of asymmetric temperature with ICR, we first propose an ICR ion transport model that couples the chemical equilibrium boundary with asymmetric temperature. In this work, ICR under different electrical boundary conditions is studied. The effects of membrane thermal conductivity, solution pH, and geometric conditions on the rectification performance are further explored in combination with surface charge and temperature dependence. The results show that the rectification ratio of the constant σ model and constant ζ model has a significant deviation compared to the multi-ion model, and the electrical boundary conditions can be simplified by changing the external conditions. By controlling the thermal conductivity of the membrane, the distribution of temperature difference within the reservoir or nanochannel can be determined, which affects the enrichment or depletion of ions in the nanochannel and ultimately achieves the goal of optimizing the rectification ratio. The optimal ICR ratio can be obtained by adjusting pH, and optimizing geometric conditions can significantly improve rectification performance. These studies provide helpful information for ion transport control and optimization of micro/nanofluid devices.

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.

Electricity-Wettability Controlled Fast Transmission of Dopamine in Nanochannels.

Achieving fast transmembrane transmission of molecules in organisms is a challenging problem. Inspired by the transport of Dopmine (DA) in organisms, the DA transporter (DAT) binds to DA in a way that has a ring recognition (the recognition group is the tryptophan group). Herein, D-Tryptophan-pillar[5]arene (D-Trp-P5) functionalized conical nanochannel is constructed to achieve fast transmission of DA. The D-Trp-P5 functionalized nanochannel enables specific wettability recognition of DA molecules and has great cycle stability. With the controlling of voltage to wettability, the transport flux of DA is up to 499.73nmol cm-2 h-1 at -6V, 16.88 times higher than that under positive voltages. In response to these results, a high-throughput DA transport device based on controlled electricity-wettability is provided.

A highly sensitive nanochannel device for the detection of SUMO1 peptides.

SUMOylation is an important and highly dynamic post-translational modification (PTM) process of protein, and its disequilibrium may cause various diseases, such as cancers and neurodegenerative disorders. SUMO proteins must be accurately detected to understand disease states and develop effective drugs. Reliable antibodies against SUMO2/3 are commercially available; however, efficient detectors are yet to be developed for SUMO1, which has only 50% homology with SUMO2 and SUMO3. Here, using phage display technology, we identified two cyclic peptide (CP) sequences that could specifically bind to the terminal dodecapeptide sequence of SUMO1. Then we combined the CPs and polyethylene terephthalate conical nanochannel films to fabricate a nanochannel device highly sensitive towards the SUMO1 terminal peptide and protein; sensitivity was achieved by ensuring marked variations in both transmembrane ionic current and Faraday current. The satisfactory SUMO1-sensing ability of this device makes it a promising tool for the time-point monitoring of the SENP1 enzyme-catalyzed de-SUMOylation reaction and cellular imaging. This study not only solves the challenge of SUMO1 precise recognition that could promote SUMO1 proteomics analysis, but also demonstrates the good potential of the nanochannel device in monitoring of enzymes and discovery of effective drugs.

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.

Effect of charge density distribution of polyelectrolyte layer on electroosmotic flow and ion selectivity in a conical soft nanochannel

Electroosmotic flow (EOF) and ion transport through a conical nanochannel coated with polyelectrolyte layer (PEL) are numerically investigated. The diffuse character is defined by an ununiform distribution of the polymer segment density. Soft step (Type I), exponential (Type II), and sigmoidal (Type III) functions were considered to describe the charge density distribution of PEL. A nonlinear model based on the Poisson-Nernst-Planck and the Navier–Stokes equations is used. The equations were solved using the finite element method. At applied voltages of ±1V, the electroosmotic velocity within diffuse soft nanochannels follows the order of uTypeI>uTypeII>uTypeIII. The soft step function leads to more ion selectivity. Considering a charge density of 100 mol/m3 and a salt concentration of 100 mM, we demonstrate that the rectification factors for the conical nanochannels, from 3 by considering the uniform PEL, can reach the value of 18 by considering the soft step function for PEL.

Fabrication of double conical PET nanochannel for molecular detection

Polymer nanochannels based on ion-track etching have attracted increasing interests for molecule detection using current blockage because of the easy control of nanochannel with precise geometry at 1 nm scale in recent years. In this work, polyethylene terephthalate (PET) membranes were irradiated with single ions of 2.15 GeV Kr and then the single latent ion track was developed to fabricate nanochannels of several nanometers for lambda-DNA detection. The ion-track etching with DC or AC provided reliable fabrication of double conical nanochannel with similar size of 48 kb λDNA with symmetrical ion transportation. Current blockage experiments demonstrated that the bi-conical PET nanochannel is sensitive for the translocation of 48 kb λDNA biomolecules with the mean translocation blockage factor Δi/i from 0.02 to 0.10 and the ability to differentiate the number of molecules. The nanochannel is more sensitive for biomolecule detection at lower KCl concentration. This investigation demonstrates that latent track etching of energetic heavy ions is a reliable approach in polymer nanochannel fabrication for biomolecule detection with accurate nanoscale control and low-cost mass production.

Ion current rectification in asymmetric charged bilayer nanochannels

At present, little attention has been paid to the ion current rectification (ICR) performance in the bilayer nanochannel with non-uniform charge distribution, which has the similar asymmetrical property with the conical nanochannel. In this work, we have established the ions transport model in the bilayer nanochannel with the coupled Poisson-Nernst-Planck (PNP) equations. Four configuration types bilayer nanochannel are compared on the ion rectification performance. The results show that asymmetrical geometry without the surface charge cannot induce ICR and the existence of surface charge is necessary. Besides, the config.3 has the best ICR performance and the physical mechanisms are discussed in detail. It is found that the ICR performance can be enhanced by regulating the surface charge density, geometry parameters and ion concentration. The ICR ratio increases as the absolute surface charge density increases and the effect is more significant to the change of left nanopore. When the total length of the bilayer nanochannel is fixed, the ICR ratio increases first and then decreases with the increasing length of the left nanopore. In addition, the forward current is more sensitive to the change of diameter of left nanopore and the reverse current is more sensitive to the change of diameter of right nanopore. When the bulk concentration varies, the ICR ratio decreases with the increasing concentration. The research results provide useful information for ions transport control and optimization of micro/nano fluidic devices.

Smart pH-Modulated Two-Way Photoswitch Based on a Polymer-Modified Single Nanochannel.

In this article, we have demonstrated a smart pH-modulated two-way photoswitch that can reversibly switch ion transport under alternating light exposure over a wide pH range. This photoswitch was prepared by functionalizing the interior of a single conical glass nanochannel with a poly-spiropyran-linked methacrylate (P-SPMA) polymer through surface-initiated atom transfer radical polymerization. The P-SPMA polymer brushes comprise functional groups that are responsive to light and pH, which can cause configuration and charge changes to affect the properties of the nanochannel wall. The SPMA polymer-modified nanochannel not only reversibly controlled ion transport under alternating light irradiation but also efficiently and flexibly regulated the direction and extent of the ion transport based on the pH. This two-way photoswitch exhibits the considerable potential of photoresponsive polymers for the advancement of "intelligent" bionic nanochannel devices for ion screening and optical sensing in various applications.

Selective detection of preferential activity of Lanthanum ion at zinc oxide functionalized nanochannel

A significant increase of rare earth transition metals concentration in water reservoirs caused by the dumping of household materials and petrol-producing industries is a potential threat to human and aquatic life. Here, we demonstrate a model nanofluidic channel for the Lanthanum (La3+) ions recognition. To this end, a single conical nanochannel is first modified with poly allylamine hydrochloride followed by immobilization of synthesized ZnO nanoparticles on the channel surface through electrostatic adsorption. A significant change in the nanopore electrical readout is noticed when the functionalized nanochannel is exposed to an electrolyte solution having La3+ cations. The distinctive response by the nanofluidic system towards La3+ ions is assumed to be due to ionic radii, hexagonal crystal structure, and associated basal plane interaction between anchored ZnO nanoparticles and La3+ ions. We anticipate that this nanofluidic system can be used as a model to design highly sensitive metal ion detection devices.

Front Cover: Fabrication and Functioning of Magnetically Gated PET Nanochannels (ChemNanoMat 7/2020)

A magnetically controlled conical nanochannel is fabricated by grafting ferroferric oxide nanoparticles into the polyethylene terephthalate (PET) nanochannel via bridging of DNA single strands. The nanochannel can be physically closed/opened to control the ionic/molecular transport in the nanochannel within sub-seconds using a permanent magnet. This mechanism may shine light on pigeon homing under the Earth's magnetic field, and could be widely used in noncontact control of micro/nanofluidic devices, as well as in smart drug delivery (superficial paste) controlled by external magnets. The background shows the colorful Danxia landform of rich iron ore in Zhangye, China. More information can be found in the Full Paper by Guanghua Du et al.

Nanochannel sensor for sensitive and selective adamantanamine detection based on host-guest competition

The abuse of adamantanamine (ADA) and its derivatives as veterinary drugs in the poultry industry could cause severe health problems for humans. It is of great need to develop a rapid, cheap and ultrasensitive method for ADA detection. In this study, a sensitive conical nanochannel sensor was established for the rapid quantitative detection of ADA with the distinctive design of the host-guest competition. The sensor was constructed by functionalizing the nanochannel surface with p-toluidine and was then assembled with Cucurbit [7]uril (CB [7]). When ADA is added, it could occupy the cavity of CB [7] due to the host-guest competition and makes CB [7] to release from the CB [7]-p-toluidine complex, resulting in a distinct change of hydrophobicity of the nanochannel, which could be determined by the ionic current. Under the optimal conditions, the strategy permitted sensitive detection of ADA in a linear range of 10–1000 nM. The nanochannel based ADA sensing platform showed both high sensitivity and excellent reproducibility and the limit of detection was 4.54 nM. For the first time, the rapid and sensitive recognition of an illegal medicine was realized based on the host-guest competition method with the nanochannel system and the principle and feasibility of this method were described at length. This strategy provides a simple, reliable, and effective way to apply host-guest system in the development of nanochannel sensor for small-molecule drug detection.

Electrokinetic power generation in conical nanochannels: regulation effects due to conicity.

Electrokinetic power generation is a promising clean energy production technology, which utilizes the electric double layer in a nanochannel to convert the hydrodynamic energy to electrical power. Previous research largely focused on electrokinetic power generation in nanochannels with a uniform cross-section. In this work, we perform a systematic investigation of electrokinetic power generation in a conical nanochannel. For this purpose, a multiphysical model consisting of the Planck-Nernst-Poisson equations and the Navier-Stokes equation is formulated and solved numerically. In particular, we discover various regulation effects in electrokinetic power generation in conical nanochannels, which manifest as the difference in the power generation characteristics (streaming potential, streaming current and current-voltage relationship) between two opposite pressure differences of the same magnitude. These regulation effects are found to originate from the conicity of the nanochannel. Furthermore, the regulation parameters are defined to quantify the observed regulation effects. Various regulation parameters can be up to severals tens of percent under extreme conditions (e.g., large pressure difference, high surface charge density or large conicity), indicating the substantial significance of the regulation effects in electrokinetic power generation. The conclusions from this work can serve as an important reference for the design and operation of nanofluidic electrokinetic power generation devices.

Pressure-driven energy conversion of conical nanochannels: Anomalous dependence of power generated and efficiency on pH

Pressure-driven power generation is one of a simple, green, and promising energy sources. Owing to the overlapping of the electric double layer inside, nanochannel is capable of providing a platform for this power generation approach. Unfortunately, relevant studies, either experimental or theoretical, are very limited in the literature. Here, we present for the first time a comprehensively theoretical study on the pressure-driven energy conversion in a conical nanochannel having carboxyl functional groups, focusing on the influence of its tip size and the solution pH. An anomalous dependence of both the power generated and the efficiency on the latter are observed. Although the charge density on the nanochannel surface increases monotonically with increasing pH, both the power generated and the efficiency exhibit a local maximum as pH varies. This is because the streaming potential has a local maximum as pH varies. Power density (power generated/tip end cross sectional area) also shows a local maximum as the tip radius varies, and the radius at which the local maximum occurs decreases with increasing bulk salt concentration. In addition to explain successfully the behavior reported in the literature, our study also provides desirable and necessary information for designing relevant devices.

Electrical Field Regulation of Ion Transport in Polyethylene Terephthalate Nanochannels.

Rectified ion transport in nanochannels is the basis of ion channels in biological cells and has inspired emerging nanochannel applications in ion separation, Coulter counters, and biomolecule detection and nanochannel energy harvesters. In this work we fabricated a polyethylene terephthalate (PET) conical nanochannel using latent ion track etching technique and then systematically studied the ion transport and influence of cation species on the nanochannel surface with cyclic I-V measurement. We discovered the electrical regulation of the reversible and irreversible modification of the nanochannel transportation by bivalent and trivalent cations, revealing the existence of the switching threshold voltage which can control the current rectification in bivalent solution. The proposed mechanism of the transport state transition in the PET nanochannel mimics behaviors of voltage-gated biological ion channels. These findings provide new insight into the understanding of the ion channel signaling and translocation control of charged particles in nanochannel applications.