Ion Reservoir Research Articles

Two birds with one stone: Copper metal-organic framework as a carrier of disulfiram prodrug for cancer therapy

Disulfiram (DSF) has a copper (II)-potentiated anticancer activity in various cancers. Synchronous delivery of DSF and cupric ions to tumor tissues is challenging but holds great potential in improving antitumor outcomes and promoting clinical translation. Herein, we reported a disulfiram prodrug (DQ)-loaded and glucose oxidase (GOD) conjugated copper (II)-based nanoscale metal–organic framework (MOF), MPDG, for tumor-specific, enhanced chemo-chemodynamic therapy. Copper MOF, MOF-199, played a dual role of drug nanocarrier of DQ and copper ion reservoir for sufficient generation of copper (II) diethylthiocarbamate (Cu(DTC)2), a complex of DSF and Cu2+. GOD improved the stability of Cu(II) nano-depot and enabled catalytic generation of H2O2 in response to high concentration of glucose in cancer cells. The catalytically generating and endogenous H2O2 boosted the activation of encapsulated H2O2-activatable prodrug DQ to generate highly cytotoxic Cu(CDTC)2 in situ for tumor-specific chemotherapy. Meanwhile, the elevated H2O2 significantly augmented the production of OH for enhanced chemodynamic therapy. The self-activated amplified chemo-chemodynamic therapy nanosystem led to a significantly enhanced inhibition of 4T1 murine breast cancer cells (half inhibitory concentration reduced from 5 μg/mL to 0.8 μg/mL) in the presence of glucose. The in vivo study verified that MPDG showed the highest tumor inhibition rate of 86.2% and negligible toxicity to main organs. Overall, this study provides a novel disulfiram prodrug/Cu2+ co-delivery strategy for enhanced and selective cancer treatment.

A Three-Dimensional Activated Carbon Electrode with Carbon Fiber Felt Framework and Ordered Macropores for Enhanced Capacitive Deionization Performance

Capacitive deionization (CDI) is a promising energy-efficient electrochemical water treatment technology and a scalable electrode having high mass loading is an essential imperative to the success of this technology. A thick CDI electrode was constructed by loading activated carbon particles as the electroactive material into a three-dimensional framework fabricated from a mixture felt of conductive carbon fiber serving as an electron transfer channel and removable yak hair functioning to provide an ion transport pathway. The carbon fiber reduces the electrode electrical resistance and the ultimately removed yak hair creates an ordered macropore array that provides an ion reservoir as well as a conduction channel for reducing ion transport distance inside the electrode. The resulting composite electrode with an optimal carbon fiber and yak hair content shows a specific capacitance of 219.27 F g-1 at 0.1 A g-1 and reaches salt adsorption capacity of 15.75 mg g-1 and average salt adsorption rate of 17.10 mg g-1 h-1 with more than 50% retention after 200 cycles. The designed three-dimensional composite exhibits enhanced deionization and long-term stability that is believed to be a low-cost and simple assembly solution for achieving a high mass loading and scalable electrode for the industrial CDI applications.

Smart PMMA‑cerium oxide anticorrosive coatings: Effect of ceria content on structure and electrochemical properties

Organic-inorganic hybrids are considered an effective and environmentally compliant alternative to chromate-based anticorrosive coatings, currently banned due to the high toxicity of hexavalent chromium. In this work, hybrid nanocomposites based on poly(methyl methacrylate) (PMMA), covalently bonded to cerium oxide nanoparticles through the 2-hydroxyethyl methacrylate (HEMA) coupling agent, were tailored by carefully tuning the inorganic colloidal precursor to provide films with active corrosion protection for metallic substrates. Lithium hydroxide was exploited as oxidizing agent of cerium nitrate to form ceria nanoparticles. Precursor solutions and solid nanocomposites with different LiOH to Ce(NO3)3.6H2O molar ratios were analyzed using spectroscopic and electron microscopy techniques and theoretical simulations. Electrochemical impedance spectroscopy (EIS) was used to study the anticorrosive performance of the coatings on carbon steel and 7075 aluminum alloy. The results showed that increasing amounts of LiOH lead to the formation of higher ceria content and larger primary nanoparticles, ranging from 1.7 to 2.8 nm. The homogenous ~20 μm-thick coatings present excellent anticorrosive performance on carbon steel and AA7075 substrates. Coatings on carbon steel with low LiOH loading (1Li:1Ce) showed long-term durability and high impedance modulus of up to 29 GΩ cm2 after 1 day in saline solution. On the AA7075 alloy, the presence of larger cerium oxide particles at higher LiOH content (3Li:1Ce) acted as effective reservoirs of cerium ions, providing high barrier coatings (395 GΩ cm2) with active corrosion protection.

Biodegradable Upconversion Nanoparticles Induce Pyroptosis for Cancer Immunotherapy

Pyroptosis, which is a mode of programmed cell death, has proven effective for cancer therapy. However, efficient pyroptosis inducers for tumor treatment are limited. This study proposes biodegradable K3ZrF7:Yb/Er upconversion nanoparticles (ZrNPs) as pyroptosis inducers for cancer immunotherapy. ZrNPs, which are similar to ion reservoirs, can be dissolved inside cancer cells and release high amounts of K+ and [ZrF7]3- ions, resulting a surge in intracellular osmolarity and homeostasis imbalance. This further induces an increase in reactive oxygen species (ROS), caspase-1 protein activation, gasdermin D (GSDMD) cleavage, and interleukin-1β (IL-1β) maturity, and results in cytolysis. In vivo tests confirm that ZrNPs-induced pyroptosis exhibits superior antitumor immunity activity confirmed by enhanced dendritic cells (DCs) maturity and frequency of effector-memory T cells, as well as observably inhibiting tumor growth and pulmonary metastasis. This work is believed to extend the biomedical applications of upconversion nanomaterials and deepen the understanding of intrinsic immunomodulatory activity of nanomaterials.

Nanoscale molecular architecture controls calcium diffusion and ER replenishment in dendritic spines.

Dendritic spines are critical components of neuronal synapses as they receive and transform synaptic inputs into a succession of calcium-regulated biochemical events. The spine apparatus (SA), an extension of smooth endoplasmic reticulum, regulates slow and fast calcium dynamics in spines. Calcium release events deplete SA calcium ion reservoir rapidly, yet the next cycle of signaling requires its replenishment. How spines achieve this replenishment without triggering calcium release remains unclear. Using computational modeling, calcium and STED superresolution imaging, we show that the SA replenishment involves the store-operated calcium entry pathway during spontaneous calcium transients. We identified two main conditions for SA replenishment without depletion: a small amplitude and a slow timescale for calcium influx, and a close proximity between SA and plasma membranes. Thereby, spine’s nanoscale organization separates SA replenishment from depletion. We further conclude that spine’s receptor organization also determines the calcium dynamics during the induction of long-term synaptic changes.

Physics-Based Stochastic Three-Dimensional Modeling for Metal–Oxide Resistive Random Access Memory

In this work, a fully physics-based stochastic 3-D modeling of metal–oxide-based resistive random access memory (RRAM) device has been conducted. In contrast to general 1-D or 2-D modeling of RRAM devices, 3-D modeling is able to provide a picture of the evolution of the 3-D random distributions of oxygen vacancies and temperature inside the device during the forming and SET/RESET processes. The modeling confirms that a tunneling gap between the top electrode (TE) which serves as an oxygen ion reservoir and the tip of the conductive filament may form at a high resistive state, which is assumed in the frequently used compact models of RRAM devices. The modeling shows that the sites with high temperature are concentrated in a cylindrical region at the center of the RRAM device, running from the inert bottom electrode to the TE. The modeling can reproduce both typical current-voltage characteristics of metal–oxide RRAM devices in forming and RESET and SET operations under a dc voltage sweep and the modulation of RRAM conductance by SET/RESET pulses.

High switching uniformity and 50 fJ/bit energy consumption achieved in amorphous silicon-based memristive device with an AgInSbTe buffer layer

In this work, we demonstrated the high switching uniformity and 50 fJ/bit energy consumption in an amorphous silicon-based resistive switching (RS) device by inserting the AgInSbTe (AIST) layer between the silicon insulating layer and Ag top electrodes. The improved RS performance is attributed to the introduction of an Ag ion reservoir layer, which helps to suppress conducting filament overgrowth. After insertion of the AIST layer, the cumulative probability of low/high resistance states decreased from 176.8%/46.2% to 3.1%/11.9%, respectively. The advantages of promoting Ag dissolution enable the realization of fast switching speed (<50 ns) and low set voltage (∼70 mV), which gives our device low energy consumption (∼50 fJ/bit). Moreover, the multi-step of set/reset analytical model of our dual-layer RS device was developed based on the formation and dissolution of the Ag-ion-based conductive filaments. Our work presents an effective method for obtaining high-performance Si-based memory for practical applications.

Neutralization and Salt Effect on the Structure and Mechanical Properties of Polyacrylic Acid Gels under Equivolume Conditions.

The effects of neutralization and salt on the structure and mechanical properties of polyacrylic acid (PAA) gels under equivolume conditions were investigated by small-angle X-ray scattering (SAXS) measurements and tensile tests. We attained the equivolume condition by immersing a piece of PAA gel sample in an ion reservoir containing linear PAA, NaOH, and NaCl at prescribed concentrations (post-ion-tuning). The volume fraction of the linear polymer was set to be the same as that of the gel so as to satisfy the iso-osmotic pressure at the reference state. Various types of reservoirs were prepared by adding NaOH and/or NaCl with different concentrations to the reference reservoir, followed by immersing a PAA gel piece. In the SAXS measurements, a scattering peak appeared, and the scattering intensity at q = 0 decreased by neutralization, while the addition of salt increased the scattering intensity. On the other hand, Young’s modulus measured with the tensile test decreased with neutralization; however, it scarcely changed with the addition of salt. The newly developed equivolume post-ion-tuning technique may serve as a new standard scheme to study polyelectrolyte gels.

Improving Performance by Inserting an Indium Oxide Layer as an Oxygen Ion Storage Layer in HfO₂-Based Resistive Random Access Memory

This study investigates an improvement in memory characteristics through depositing an In2O3 layer as an oxygen ion reservoir in the switching layer (SL) of resistive random access memory (RRAM). The deposition of In2O3, denoted as Pt/HfO2/In2O3/TiN device, provides better memory characteristics including lower forming voltage ( ${V}_{F}$ ), set/reset voltage ( ${V}_{\mathrm {SET}}/{V}_{\mathrm {RESET}}$ ), larger memory window, and higher resistances with higher uniformity at low resistance state (LRS) and high resistance state (HRS), compared to the devices without the In2O3 deposition, denoted as Pt/HfO2/TiN device. The conduction mechanisms, verified through fitting current–voltage ( ${I} - {V}$ ) curves, are consistent with the results of a varied temperature ${I} - {V}$ experiment. Finally, a physical model is proposed to explain our observations.

Extraction and transport of low-energy Ar ion beams with a broad cross-section

Low-energy argon (Ar) ion beams were accelerated from a quiescent discharge in a custom-designed ion reservoir. Around 100 eV Ar ion beams were extracted from an ion source with different multi-cusp magnetic field configurations through a 4-cm diameter two-electrode extraction system. Langmuir probe measurements correlated the source plasma characteristics to the extracted ion beam properties that were determined using a retarding potential analyzer and a moving Faraday cup. The ion extractor configuration allowed primary electrons from the ion reservoir to seep downstream to neutralize the space-charge of the Ar ions. The broad cross-section ion beam system is designed for material synthesis and surface modification.

Effect of nitrogen capture ability of quantum dots on resistive switching characteristics of AlN-based RRAM

This Letter studies the effect of the nitrogen capture ability of quantum dots on resistive switching characteristics of AlN-based resistive random access memory. We prepared a single layer AlN device and four types of AlN/PbS quantum dot stacked structure devices with different concentrations. Compared with the single layer AlN device, the AlN/PbS quantum dot stacked structure devices exhibit excellent resistive switching characteristics, such as forming-free, low power consumption, and excellent stability. We propose that the resistive switching process is determined by the migration of nitrogen ions and the lead sulfide (PbS) quantum dot layer as a natural nitrogen ion reservoir, which can improve the resistive switching characteristics. Moreover, the size of the natural nitrogen ion reservoir can be modulated by changing the concentration of quantum dots.

Core–shell ZIF-8@polydopamine nanoparticles obtained by mitigating the polydopamine coating induced self-etching of MOFs: prototypical metal ion reservoirs for sticking to and killing bacteria

ZIF-8@PDA nanoparticles can work as metal ion reservoirs that locally release metal ions to kill bacteria after sticking to them.

Hierarchical NiO@Ni(OH)2 nanoarrays as high-performance supercapacitor electrode material

A binary metal oxide/hydroxide as a hierarchical NiO@Ni(OH)2 nanoarrays was synthesized through several steps. Firstly, ZnO nanorods were prepared through a facile electrodeposition method on Ni foam (NF), and then the obtained ZnO nanorods were used as sacrificed template to deposit NiO nanotubes around them. The obtained nanotubes served as ideal 1D superhighways for charge storage and ion delivery. After that, chemical bath deposition was used to decorate Ni(OH)2 nanoflakes on top of NiO nanotubes acting as an ion reservoir. The prepared electrodes were evaluated by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) methods. More advanced characterizations of the NF/NiO nanotubes and NF/NiO@Ni(OH)2 nanoarrays were performed using Fourier transform infrared (FT-IR) and Raman spectroscopy, Thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods. Compared with the single NiO nanotubes or Ni(OH)2 nanoflakes, the NiO@Ni(OH)2 nanoarrays exhibited a high specific capacitance (Csp) of 2509 mA cm-2 at 1 mA cm-2. Long term cycling stability observed over 5000 cycles without negligible loss of Csp. This study shows that hierarchical covering metal oxide channels with the metal hydroxide flakes can open up new strategies for the design of high-performance supercapacitor electrode materials.

Electrode-induced polarity conversion in Nb2O5/NbOx resistive switching devices

Applications in neuromorphic computing and next-generation memories require a deep understanding of the physical mechanisms in resistive switching (RS) devices. Here, we report electrode-induced polarity conversion in Nb2O5/NbOx RS devices, where Nb2O5 and NbOx are a switching layer and an oxygen vacancy (Vo··) reservoir, respectively. The reservoir provides the Vo·· s, comprising a conductive filament formed during an electroforming process. After the process, the devices with an inert Pt top electrode show a clockwise RS behavior. However, the ones with a reactive W top electrode exhibit a counterclockwise RS behavior. Detailed explorations suggest that reactive electrodes provide an oxygen ion reservoir near the active region of the conductive filaments. The reservoir dominates the rupture and recovery of the conductive filaments through interfacial redox reaction, which induces the switching polarity conversion. This study indicates that oxygen ion distribution and migration near a conductive filament tip have the dominant effect on switching processes of oxide RS devices.

Molten salt-confined pyrolysis towards carbon nanotube-backboned microporous carbon for high-energy-density and durable supercapacitor electrodes

The development of a green and scalable construction of a three-dimensional (3D) hierarchically porous carbon as an electrode material for supercapacitors is promising but challenging. Herein, a carbon nanotube-backboned microporous carbon (CNT-MPC) was prepared by molten salt-confined pyrolysis, during which the salt eutectics simultaneously acted as a high-temperature reaction solvent and reusable template. Among the CNT-MPC, the CNT backbone provided a 3D conductive framework, whereas the MPC sheath possessed integrated mesopores and micropores as an efficient ion reservoir. As a result, the as-obtained CNT-MPC exhibited a high specific capacitance of 305.6 F g−1 at 1 A g−1, high energy density of 20.5 W h kg−1 and excellent cyclic stability with no capacitance losses after 50 000 cycles. The molten-salt confined pyrolysis strategy therefore provides a low-cost, environmentally-friendly and readily industrialized route to develop a hierarchically porous carbon that is highly required for high-energy-density and durable supercapacitors.

Three-dimensional electrode design with conductive fibers and ordered macropores for enhanced capacitive deionization performance

Capacitive deionization (CDI) is a promising energy-efficient electrochemical water treatment technology and a scalable electrode having high mass loading is an essential imperative to the success of this technology. A thick CDI electrode was constructed by loading activated carbon particles as the electroactive material into a three-dimensional framework fabricated from a mixture felt of conductive carbon fiber serving as an electron transfer channel and removable yak hair functioning to provide an ion transport pathway. The carbon fiber reduces the electrode electrical resistance and the ultimately removed yak hair creates an ordered macropore array that provides an ion reservoir as well as a conduction channel for reducing ion transport distance inside the electrode. The resulting composite electrode with an optimal carbon fiber and yak hair content shows a specific capacitance of 219.27 F g−1 at 0.1 A g−1 and reaches salt adsorption capacity of 15.75 mg g−1 and average salt adsorption rate of 17.10 mg g−1 h−1 with more than 50% retention after 200 cycles. The designed three-dimensional composite exhibits enhanced deionization and long-term stability that is believed to be a low-cost and simple assembly solution for achieving a high mass loading and scalable electrode for the industrial CDI applications.

Microfabricated Ion-Selective Transistors with Fast and Super-Nernstian Response.

Transistor-based ion sensors have evolved significantly, but the best-performing ones rely on a liquid electrolyte as an internal ion reservoir between the ion-selective membrane and the channel. This liquid reservoir makes sensor miniaturization difficult and leads to devices that are bulky and have limited mechanical flexibility, which is holding back the development of high-performance wearable/implantable ion sensors. This work demonstrates microfabricated ion-selective organic electrochemical transistors (OECTs) with a transconductance of 4mS, in which a thin polyelectrolyte film with mobile sodium ions replaces the liquid reservoir. These devices are capable of selective detection of various ions with a fast response time (≈1s), a super-Nernstian sensitivity (85mVdec-1 ), and a high current sensitivity (224µAdec-1 ), comparing favorably to other ion sensors based on traditional and emerging materials. Furthermore, the ion-selective OECTs are stable with highly reproducible sensitivity even after 5 months. These characteristics pave the way for new applications in implantable and wearable electronics.

Honeycomb micro/nano-architecture of stable β-NiMoO4 electrode/catalyst for sustainable energy storage and conversion devices

Multi-functionality is a highly desirable feature in designing new electrode material for both energy storage and conversion devices. Here, we report a well-integrated and stable β-NiMoO4 that was fabricated on three dimensional (3D) nickel foam (NF) by a simple hydrothermal approach. The obtained β-NiMoO4 with interesting honeycomb like interconnected nanosheet microstructure leads to excellent electrochemical activity. As an electrode for Supercapatteries, β-NiMoO4–NF showed a high specific capacity of 178.2 mA h g−1 (916.4 F g−1) at 5 mA cm−2 current density. Most importantly, the fabricated symmetric device exhibits a maximum specific energy of 35.8 W h kg−1 with the power output of 981.56 W kg-1 and excellent cyclic stability. In methanol electro-oxidation, the β-NiMoO4 –NF catalyst deliver the high current density of 41.8 mA cm−2 and much lower onset potential of 0.29 V with admirable long term stability. Apart from the above electrochemical activity, the β-NiMoO4 –NF honeycomb microstructure demonstrates a promising non-noble electrocatalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) and showed a considerable overpotential of 351 mV (OER) and 238 mV (HER). The attractive multifunctional electrochemical activity of β-NiMoO4–NF could be originates from their unique honeycomb micro/nano structure which can acts as an “ion reservoir” and thus leads to superior energy storage and conversion processes.

Silk Fibroin-Modified Disulfiram/Zinc Oxide Nanocomposites for pH Triggered Release of Zn2+ and Synergistic Antitumor Efficacy.

Disulfiram (DSF) is an FDA-approved anti-alcoholic drug that has recently proven to be effective in cancer treatment. However, the short half-life in the bloodstream and the metal ion-dependent antitumor activity significantly limited the further application of DSF in the clinical field. To this end, we constructed a silk fibroin modified disulfiram/zinc oxide nanocomposites (SF/DSF@ZnO) to solubilize and stabilize DSF, and, more importantly, achieve pH triggered Zn2+ release and subsequent synergistic antitumor activity. The prepared SF/DSF@ZnO nanocomposites were spherical and had a high drug loading. Triggered by the lysosomal pH, SF/DSF@ZnO could induce the rapid release of Zn2+ under the acidic conditions and caused nanoparticulate disassembly along with DSF release. In vitro experiments showed that cytotoxicity of DSF could be enhanced by the presence of Zn2+, and further amplified when encapsulated into SF/DSF@ZnO nanocomposites. It was confirmed that the significantly amplified cytotoxicity of SF/DSF@ZnO was resulted from pH-triggered Zn2+ release, inhibited cell migration, and increased ROS production. In vivo study showed that SF/DSF@ZnO nanocomposites significantly increased the tumor accumulation and prolonged the retention time. In vivo antitumor experiments in the xenograft model showed that SF/DSF@ZnO exerted the highest tumor-inhibition rate among all the drug treatments. Therefore, this exquisite study established silk fibroin-modified disulfiram/zinc oxide nanocomposites, SF/DSF@ZnO, where ZnO not only acted as a delivery carrier but also served as a metal ion reservoir to achieve synergistic antitumor efficacy. The established DSF nanoformulation displayed excellent therapeutic potential in future cancer treatment.

Ion Reservoir Enabled by Hierarchical Bimetallic Sulfides Nanocages Toward Highly Effective Sodium Storage.

Designing and constructing bimetallic hierarchical structures is vital for the conversion-alloy reaction anode of sodium-ion batteries (SIBs). Particularly, the rationally designed hetero-interface engineering can offer fast diffusion kinetics in the interface, leading to the improved high-power surface pseudocapacitance and cycling stability for SIBs. Herein, the hierarchical zinc-tin sulfide nanocages (ZnS-NC/SnS2 ) are constructed through hydrothermal and sulfuration reactions. The unconventional hierarchical design with internal void space greatly optimizes the structure stability, and bimetallic sulfide brings a bimetallic composite interface and N heteroatom doping, which are devoted to high electrochemical activity and improved interfacial charge transfer rate for Na+ storage. Remarkably, the ZnS-NC/SnS2 composite anode exhibits a delightful reversible capacity of 595 mAh g-1 after 100 cycles at 0.2 A g-1 , and long cycling capability for 500 cycles with a low capacity loss of 0.08% per cycle at 1 A g-1 . This study opens up a new route for rationally constructing hierarchical heterogeneous interfaces and sheds new light on efficient anode material for SIBs.