Herein we present an iontronic memristor using funnel-shaped Ångström channels, exhibiting behavior that differs from conventional conical nanochannel systems. Funnel-shaped channels were fabricated using ion-track technology, which consists of an Ångström tip and a conical nano-opening as the base. The voltage sweeping measurements showed current hysteresis as an essential feature of the memristor, with the hysteresis area increasing with frequency, reaching a peak, and subsequently decreasing. The current rectification becomes reversed compared to the classical conical nanochannel at low bias voltages, returning once the bias voltage surpasses a specific threshold. The reversed current rectification and unconventional hysteresis area change are likely attributed to energy barriers at the Ångström-scale tip, resulting in a decrease in ionic fluxes from the tip to the base. When the bias exceeds this threshold, the system returns to the standard conical nanochannel feature. Our research demonstrates a nanofluidic memristor in which the hysteresis and rectification are dependent on both voltage and frequency. This indicates potential applications in neuromorphic computing which can enhance the understanding of ionic transport in sub-nanometer confinement.

In this study, we investigate an innovative memristor based on a Liquid/ZnO layered structure, which we refer to as the Liquid/ZnO Combination Memristor (LZCM). This device not only extends the basic memristive functions but also explores cutting-edge applications in neuromorphic and optoelectronic domains. Building on our previous work that demonstrated the device's memristive behavior and fundamental synaptic properties, we now investigate its advanced functionalities, including paired-pulse facilitation (PPF), spike-timing-dependent plasticity (STDP), and history-dependent plasticity (HDP). These studies show the device's ability to mimic complex synaptic behaviors with unprecedented efficiency. In a practical application, we utilized five LZCMs to recognize 5 & times; 4 pixel digit images by encoding these images into temporal pulse trains, achieving highly effective image differentiation. Moreover, we integrated these memristors into a neural network to classify MNIST dataset digits, achieving a remarkable 92% recognition accuracy after 100 training epochs. In addition, the device exhibits a significant response to 365 nm UV light, where varying light intensities induce distinct photocurrent levels. This unique optoelectronic property enables the realization of logic gate functions through single and double light pulse exposure. Our findings highlight the LZCM as a groundbreaking candidate for future neuromorphic systems and advancements in optoelectronic integration and energy-efficient computing.

When nanopore dimensions approach the size of hydrated ions (sub-nanometer scale), ion transport deviates markedly from classical continuum descriptions. Under such extreme confinement, hydration-shell distortion, dielectric self-energy barriers, ion-pair dissociation, and ion-surface interactions collectively give rise to nonlinear conduction, ionic Coulomb blockade, and history-dependent ion transport. These confined phenomena provide a physical basis for fluidic memristors that emulate biological synaptic functions. This review summarizes recent advances in artificial sub-nanometer structures, anomalous ion transport mechanisms, fluidic memristors, synaptic plasticity emulation, and neuromorphic computing applications. Particular attention is paid to how confined ion transport mechanisms are translated into internal state variables of fluidic memristors, including ion-pair fraction, adsorbed ion density, concentration distribution, and wetting states. Finally, we discuss the current challenges and future opportunities in precise fabrication, mechanistic understanding, device stability, and system-level integration. This review aims to provide a mechanistic perspective for developing low-power, biomimetic, and scalable ionic neuromorphic systems.

Metal-organic frameworks (MOFs)-derived metal oxides have a high specific surface area and porous structure, making them promising for gas sensing applications. In this paper, MOFs-derived In2O3/ZnCo2O4 composites were synthesized using a two-step solvothermal method. Through a series of characterization strategies, it is revealed that the morphology of the In2O3/ZnCo2O4 composites consists of hollow microtubes and microflowers. The gas sensing performance of In2O3/ZnCo2O4 composites was significantly enhanced compared to pure In2O3. Among them, the In2O3/ZnCo2O4-2 sensor exhibited superior performance towards 100 ppm n-butanol gas, with a lower operating temperature of 200 degrees C, a higher response value of 208.7, a lower detection limit of 4.2 ppb, shorter response/recovery times of 152 s/223 s, higher selectivity, and better repeatability. Furthermore, the improved gas response can be attributed to the utilization of MOFs as self-sacrificial templates, the high specific surface area of the sensing materials, and the formation of p-n heterojunctions. This study provides a valuable reference for synthesizing n-butanol sensing materials with a high specific surface area, strong response, and excellent selectivity.

A knowledge gap exists for flows and transport phenomena at the Angstrom scale when the Poisson Nernst Planck equation based on the concept of electrical double layer (EDL) fails. We discovered that streaming conductance becomes pressure dependent in Angstrom channels using latent track membranes. The streaming current emerges only when the applied pressure exceeds a threshold value, which is inconsistent with the existing knowledge as a constant. With increasing channel size, we found that the pressure dependent streaming conductance phenomenon weakens and vanishes into a constant streaming conductance regime when the mean channel radius exceeds 2 nm. The effective surface potential derived from the stream conductance that divides conduction anomalously increases as the channel narrows. We suspect the pressure dependent streaming current is due to the reinforced Coulomb interaction between counterions and deprotonated carboxyl groups at the surface, which is close to the ion channel but different from the electrified 2D materials. The streaming current emerged due to hydrodynamic friction when the counterions were released from the surface. We approximated the stochastic process of counterion dissociation by 1D Kramer escape theory framework and defined the Damkohler Number to describe the transition from nonlinear streaming conductance regime to linear regime as functions of applied pressure and channel radius and well explained the enhanced effective surface potential in confinement.

In this study, carbon/TiO2 composite particles were prepared by pyrolyzing metal-organic framework (MOF) particles. The structure and conductivity of composite particles was characterized and the electrorheological (ER) effect of composite particles dispersed in silicone oil was measured under electric fields. It is interesting that the composite particle suspensions exhibit a tunable electro-response from negative to positive ER effect depending on pyrolysis temperatures. The suspension containing particles produced at 400 °C shows abnormal negative ER effect, which can be explained by the conduction model because 400 °C-pyrolysis destroys the bonds between organic linkers and Ti—O clusters to yield composite with lower conductivity than silicone oil. However, the suspension containing particles produced at 440 °C still shows negative ER effect, which cannot be explained by the conduction model because the conductivity of composite exceeds that of silicone oil. Through microscopic observation and dielectric spectra analysis, we clarified that the absence of available interfacial polarization in the suspensions of particles produced at lower pyrolysis temperature than 440 °C is the real reason of negative ER effect. Increasing pyrolysis temperatures to 480 and 520 °C improves the carbonization level and conductivity of composites, leading to large interfacial polarization and positive ER effect of corresponding suspensions. The suspension containing particles produced at 520 °C exhibits the optimal positive ER effect. This work demonstrates the crucial role of interfacial polarization in determining positive or negative ER effect through using MOF-derived carbonaceous composites with tunable structure and electric properties.

As an emerging semiconductor material, Ga2O3 boasts a broader n-type band gap compared to SiC and GaN, the cornerstones of third-generation semiconductor technology. Its exceptional affinity for ethylene glycol (EG) makes it an ideal candidate for gas sensing research. However, the high operating temperatures required for Ga2O3 sensors have hindered its practical application. This study introduces CuO to form a p-n hetero-junction with Ga2O3 via a facile two-step solvothermal process. The resulting composite material establishes a space charge layer (SCL) that facilitates electron flow, enhancing the interaction between the sensing material and target gases, and significantly lowering the operational temperature. The synthesized CuO@Ga2O3 composite was meticulously characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). In addition, the correlation between gas response and operating temperature was further explored by changing the molar ratio of CuO/Ga2O3, and the gas-sensitive mechanism was analyzed. These results indicate that the study of CuO@Ga2O3 materials provides a new way to develop high-performance glycol sensors.

AbstractHere a reconfigurable memristor is demonstrated by connecting ZnO film to a fluidic channel. The memristive characteristics are successfully demonstrated with an electrolyte solution. The benefit of using a microfluidic channel is that the memristive characteristics can be adjusted by changing the electrolyte solution in real‐time. The neuromorphic functions such as long‐term plasticity, Spiking‐Rate‐Dependent Plasticity (SRDP), and behavior associated with “learning experiences”are demostrated in the devices. The capability of real‐time manipulating of memristive characteristics enables diverse manipulations on memristive characteristics of the devices, by doping of different concentrated and type of ions in the ZnO film. The electrolyte solution will open new possibilities for resistance switch manipulations, for the next generation neuromorphic computing.

Metal-organic frameworks (MOFs)-derived metal oxides are characterized by high porosity, large specific surface area, controllable composition, and tunable pore size, which make them have good potential as gas sensing materials. In this paper, Ni 3 V 2 O 8 @NiO hollow microspheres derived from bimetallic Ni/V-MOFs were synthesized using a three-step method (solvothermal method, cation-exchange method, and annealing process). XRD, Raman, SEM, TEM, XPS, and BET techniques were employed to investigate the structure, morphology, specific surface area, pore size distributions, elemental composition, and chemical state of Ni 3 V 2 O 8 @NiO composites. Gas sensing performance studies showed that the NV@NiO-2 sensor exhibited higher response (43.7) to 100 ppm triethylamine at a lower operating temperature (240 degree celsius), shorter response/recovery time (88 s/127 s), higher selectivity, lower detection limit (4.5 ppb), and better repeatability. In addition, the NV@NiO-2 sensor exhibited a strong linear relationship (R 2 = 0.996) between response and gas concentration across a range of 1 - 100 ppm. The present work serves as a valuable reference for the preparation of triethylamine sensing materials with high specific surface area, high porosity, high response and high selectivity.

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The development of nanoelectronics and nanotechnologies has been boosted significantly by the emergence of 2D materials because of their atomic thickness and peculiar properties, and developing a universal, precise patterning technology for single-layer 2D materials is critical for assembling nanodevices. Demonstrated here is a nanomachining technique using electrical breakdown by an AFM tip to fabricate nanopores, nanostrips, and other nanostructures on demand. This can be achieved by voltage scanning or applying a constant voltage while moving the tip. By measuring the electrical current, the formation process on single-layer materials was shown quantitatively. The present results provide evidence of successful pattern fabrication on single-layer MoS2, boron nitride, and graphene, although further confirmation is still needed. The proposed method holds promise as a general nanomachining technology for the future.

Metal-organic frameworks (MOFs)-derived metal oxide semiconductors (MOSs) have garnered significant interest for their potential use in gas -sensitive materials, owing to their distinctive properties. Despite this, gas sensors derived from MOFs are still hindered by issues such as low sensitivity or poor selectivity. In this research, we address these challenges by integrating MOF-derived Cr 2 O 3 nanoparticles with reduced graphene oxide (RGO) nanosheets to form p -p heterojunction composites, which significantly enhance the sensing capabilities for n-butanol gas detection. We employed a gravity-induced sedimentation technique coupled with the hydrothermal method to grow Cr 2 O 3 nanoparticles on RGO nanosheets. The RGO nanosheets not only act as a substrate to prevent the agglomeration and stacking of Cr 2 O 3 nanoparticles but also facilitate the formation of Cr 2 O 3 /RGO pp heterojunctions. Consequently, the fabricated Cr 2 O 3 /RGO sensor, with a GO weight fraction of 2.9 wt%, demonstrated an impressive response of 121.2 -100 ppm n-butanol gas at 160 degrees C, which is an eightfold increase over a sensor composed solely of Cr 2 O 3 . The theoretical detection limit was determined to be as low as 8.6 parts per billion (ppb). The study concludes with a discussion on the potential sensing mechanism of the Cr 2 O 3 /RGO composites that contribute to the enhanced performance. The findings of this research are expected to significantly advance the development and application of n-butanol detection technology.

Cr2O3 nanoparticles derived from metal-organic frameworks (MOFs) are prepared, furtherly Cr2O3/MXene composites are synthesized via two different methods (hydrothermal and mechanical stirring, respectively). Xray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) are used to characterize the structure and morphology of these samples. The gas sensing performance of these materials is being studied. The sensors based on Cr2O3/MXene composites which was synthesized by the hydrothermal method exhibits higher response (130.1) to 100 ppm n-butanol at a lower operating temperature (160 degrees C), lower detection limit (10.1 ppb), shorter response/recovery time (90 s/ 210 s), better repeatability, and higher selectivity. It has been confirmed that most of the MXene in the Cr2O3/ MXene composites synthesized by the hydrothermal method is oxidized to TiO2 and C-dots, as opposed to the mechanical stirring method. In addition, different types of heterojunctions and electron sensitization of C-dots in Cr2O3/MXene composites provides additional pathways for electron transfer, as well as more active sites for gas diffusion and adsorption, significantly enhancing gas sensing performance. This work offers promising materials for designing and preparing gas sensors for detecting n-butanol.

Metal oxides derived from metal-organic frameworks (MOFs) can maintain the porosity and unique structure of MOFs, giving them significant development potential in the field of gas sensing. In this study, bimetallic Ni/Zr-MOFs solid microspheres were synthesized via the solvothermal method, and NiO/ZrO2 composites with p-p heterostructure were further prepared through an annealing process. The morphology, structure, specific surface area, and pore size of NiO/ZrO2 composites were analyzed using a series of characterization techniques. The gas sensing performance study showed that the NiO/ZrO2-2 sensor exhibited higher response (32.3-100 ppm), lower detection limit (7.2 ppb), shorter response/recovery time (55s/83s), and excellent repeatability to triethylamine gas at the operating temperature of 240℃. Additionally, within a specific range (1-200 ppm), a strong linear relationship was observed between the response value and the gas concentration for the NiO/ZrO2-2 sensor (R2=0.9588). This study is expected to provide a valuable reference for designing high-performance triethylamine sensors.

The emergence of nanofluidic memristors has made a giant leap to mimic the neuromorphic functions of biological neurons. Here, we report neuromorphic signaling using Angstrom-scale funnel-shaped channels with poly-l-lysine (PLL) assembled at nano-openings. We found frequency-dependent current-voltage characteristics under sweeping voltage, which represents a diode in low frequencies, but it showed pinched current hysteresis as frequency increases. The current hysteresis is strongly dependent on pH values but weakly dependent on salt concentration. We attributed the current hysteresis to the entropy barrier of PLL molecules entering and exiting the Angstrom channels, resulting in reversible voltage-gated open-close state transitions. We successfully emulated the synaptic adaptation of Hebbian learning using voltage spikes and obtained a minimum energy consumption of 2-23 fJ in each spike per channel. Our findings pave a new way to mimic neuronal functions by Angstrom channels in low energy consumption.

BiOCl powders with different amounts of thiourea addition (0, 25 mg, 50 mg, 100 mg versus 8 mmol Bi(NO3)3, denoted as BOC, BOC-S1, BOC-S2, BOC-S3) in precursor were prepared by solvothermal method. In this work, thiourea generated modification of lattice structure, stimulating shrinkable Bi-O bond rather than S element doping or composite structure forming. Shrinkable Bi-O bond generated enhanced interaction between [Bi2O2]2+ and adjacent Cl-, causing stronger inner electric field. Shorter Bi-O bond endows valence band(VB) more Cl component, enhancing Cl 3p dominance. With intrinsic Bi 6p dominant conduction band, holes could transferred to VB on Cl while electrons be transferred to CB on Bi under stronger inner electric field, performing heterojunction like efficient charge separation and transfer. Prominent promotion on CO2 photocatalytic reduction was thus achieved due to improved charge separation and transfer efficiency, where BOC-S2 reach about 5.6 times higher CH4 yield than BOC with CH4 selectivity increasing from 80.673 % (BOC) to 96.473 (BOC-S2), certifying successful CO2 reduction ability promotion through lattice structure modulation.

ZnO has broad application prospects in the field of LED lighting and display. However, the unclear luminescence mechanism limits the improvement of luminous efficiency and the realization of controllable luminescence. Herein, intrinsic defects (Zni and V-O) in sol-gel ZnO thin films were controlled by post-annealed in different atmospheres (air, N-2 and vacuum). The effect of annealing atmospheres on the intrinsic defects were quantitatively studied by XRD, Raman, XPS and EPR spectra, and the relationship between intrinsic defects and visible emissions were systematically investigated by excitation-dependent PL spectra under above bandgap and below bandgap excitations. Results show that N-2-annealed ZnO film with more Zni defects and fewer Vo defects exhibits much stronger blue (~ 440 nm and-450-480 nm) and green emissions (~ 510-540 nm). Zinc interstitials states (including Zni and ex-Zni states) are the initial states of the electronic transitions for the blue (~ 440 nm and-450-480 nm) and green emissions (~ 510-540 nm). In addition, transitions from the conduction band to the VO level also emit a green peak at 525 nm, which can only be observed under above bandgap excitation. This work contributes to a better understanding of defect-induced blue and green emission in ZnO, which will help to achieve controllable luminescence and facilitate its commercial application as a luminescent material.

BiOCl powders with different amounts of Sn doping (0, 5%, 10%, 20% versus molar amount of Bi, denoting as BOC, BOC-S5, BOC-S10, BOC-S20 respectively) were prepared by solvothermal method. Sn doping resultant effect on obtained samples and their photocatalytic performance were studied. All Sn doped BiOCl showed stronger photocatalytic degradation ability towards organic dye RhB compared with undoped one, where BOC-S10 with highest performance behaved 33% higher RhB degradation than BOC. Through relevant experiments and calculations, it’s found that Sn doping stimulated more dispersive electron localization in [Bi2O2]2+ layer, favorable for carrier generation, while introduction of Sn4+ also strengthened the inner polarization along [0 0 1] direction, which improved intrinsic inner electric field revulsive carrier separation. Changes on electronic structure promoted carrier generation and transfer, providing higher photocatalytic performance. Photocatalytic reduction of CO2 manifested that Sn doped samples also behaved larger potential on synthesizing CH4 through CO2 reduction and BOC-S10 still exhibited highest performance with CH4 yield 67% higher than BOC. All the results manifested that Sn doping introduced transformation beneficial to promote photocatalytic performance.

The surface wettability can be well controlled by coatings and roughness. In this work, we prepared ZnO film and nanorods with different precursor concentration range from 0.002 mol/L, 0.02 mol/L to 0.2 mol/L on glass substrates by simple wet chemical method. We found that the range of contact angle transitions was significantly enlarged by growing nanorods on ZnO seed layer. Besides, the wettability is reversible that the ZnO nanorods turns to hydrophilic by ultraviolet irradiation and recovered to hydrophobic after heating at 180 ℃. Our results showed the nanorods with the precursor concentration of 0.02 mol/L exhibited fastest speed of the reversible transition. According to the switchable wettability, the aggregated large droplet on the hydrophobic solid surface tends to swallow other microdroplets in the opposite direction of the jet trajectory, and then, the surface was easily non-contact patterned, which is conducive to the further realization of large-scale applications as smart surfaces.

BiOCl powders with different morphology were obtained through self-assembling. Their photocatalytic performance was tested through degradation of organic dye and mechanism of photocatalytic for obtained samples were investigated. Relevant characterization demonstrated that facet synergy was a main reason of photocatalytic performance promotion due to changed facet exposure and proportion under self-assembling. Theory and experimental analysis manifested that synergistic facet stimulated Z scheme transition in samples with lower (001) facet proportion, which provided favorable condition of 1O2 generation and simultaneously generated prominent charge separation. This work unveiled the facet synergy dominant photocatalytic performance improvement in self-assembling system of BiOCl and verified decisive role of facet proportion in constructing Z-scheme facet junction, which also prompted possibility of improving 1O2 generation through facet engineering under self-assembling.