Unipolar Ionic Diode Nanofluidic Membranes Enabled by Stepped Mesochannels for Enhanced Salinity Gradient Energy Harvesting

Interfacial Mesochannels as Cation Pump for Enhanced Osmotic Energy Harvesting

Membranes integrating 1D materials are rapidly emerging as highly promising platforms for osmotic energy harvesting. However, their power output is often constrained by insufficient ion selectivity. Herein, we demonstrate a cation pumping strategy by designing mesoporous silica coated multiwalled carbon nanotubes/aramid nanofiber (MCNTs@mSiO2/ANF) composite membranes as osmotic power generators. Cations can be initially enriched in the negatively charged and small-pore-sized (∼ 3 nm) interfacial mesopore channels, establishing a strong cation concentration gradient toward the interfiber nanochannels. The gradient continuously drives cations into the interfiber pores, facilitating charge separation, and improving ion selectivity. Additionally, the hydrophilic nature of the mesoporous silica shells promotes ion transport and contributes to high ion flux. Consequently, the fabricated MCNTs@mSiO2/ANF composite nanochannel membranes can deliver a notable power density of 8.24 W m-2 with an excellent ion selectivity of 0.91 under a 50-fold NaCl salinity gradient. Importantly, the membranes demonstrate long-term stability for osmotic energy capturing. When placed between natural seawater and river water, the composite membranes yield an impressive power density of 9.93 W m-2, surpassing that of the state-of-the-art 1D material-based membranes. This work paves the way for the practical applications of nanofiber-based membranes in sustainable osmotic energy conversion.

Tandem Assembly and Etching Chemistry towards Mesoporous Conductive Metal-Organic Frameworks for Sodium Storage Over 50,000 Cycles

Despite two-dimensional (2D) conductive metal-organic frameworks (cMOFs) being attractive due to their intrinsic electrical conductivity and redox activity for energy applications, alleviating the constrained mass transfer within long-range micropore channels remains a significant challenge. Herein, we present a tandem assembly and etching chemistry, to incorporate perpendicularly aligned mesopores into the micropores of cMOFs, via a bi-functional modulator. Synchrotron spectral and morphological analyses demonstrate that the elaborate ammonia modulator first coordinates with Zn2+ forming defects during the initial self-assembly of cMOF oligomers, which then initiates mesoporous cMOFs via in situ etching. In situ spectroscopy and theoretical simulations further reveal that such a unique perpendicular mesoporous structure shorts the micropore channels by two orders of magnitude and relaxes the inherent ion stacking within micropores, leading to five times faster Na+ transport and a remarkable rate capability at 250 C and sodium storage lifespan over 50,000 cycles. Our protocol opens up a new avenue for introducing mesopores into microporous cMOFs for advanced energy applications and beyond.

Electrochemical Sensing Mechanisms and Interfacial Design Strategies of Mesoporous Nanochannel Membranes in Biosensing Applications

Precise and rapid detection of key biomolecules is crucial for early clinical diagnosis. These critical biomolecules and biomarkers are typically present at low concentrations within complex environments, presenting significant challenges for their accurate and reliable detection. Nowadays, electrochemical sensors based on nanochannel membranes have attracted significant attention due to their high sensitivity, simplicity, rapid response, and label-free point-of-care detection capabilities. The confined arena provided by the nanochannels for target recognition and interactions facilitates detection and signal amplification, leading to enhanced detection performance. The nanochannel membranes also can act as filters to repel the interferents and enable target detection in more complex environments. Thus, sensors based on nanochannel membranes are considered promising platforms for biosensing applications. However, challenges such as uncontrollable structures and unstable performance in some materials limit their applications and theoretical advancements. To investigate the relationship between architecture and sensing performance and to achieve reliable and efficient performance, it is essential to construct sensors with precise nanostructures possessing stable properties. With the development of nanomaterials technology, mesoporous nanochannel membranes with robust, controllable, and ordered mesostructures, along with tunable surface properties and tailored ion transport dynamics, have emerged as promising candidates for achieving reliable and efficient biosensing performance. Additionally, investigating the sensing mechanisms and key influencing factors will provide valuable insights into optimizing sensor architecture and enhancing the efficiency and reliability of biosensing technologies. In this Account, we highlight substantial advancements in mesoporous nanochannel membranes, which are mainly based on the research work published by our group. In the first section, we explore the underlying mechanisms of the sensing processes, including the solid-liquid interfacial interactions and nanoconfinement effects (i.e., electrostatic interactions, hydrophilic/hydrophobic interactions, and steric hindrance effects). We also delve into the key parameters including geometry, materials, recognition elements, and external factors related to mesoporous nanochannel membranes and their impacts on sensing mechanisms and performance. In particular, we point out that mesoporous nanochannel membranes with three-dimensional interconnected networks can facilitate ion penetration and lead to an increased number of binding sites, contributing to high sensitivity. Additionally, composite or multilevel mesoporous nanochannel membranes, particularly when integrated with external stimuli such as pH, light, and heat, can introduce unexpected properties, enhancing the sensing performance. These understandings provide valuable insights into the fundamental principles and influencing factors pertinent to the research and design of intelligent, high-quality sensors or nanofluidic devices. Furthermore, we conduct an analysis of integrating various biosensing mechanisms and strategies, which offers significant opportunities for biomedical monitoring, disease diagnosis, and the pharmaceutical industry. Finally, we describe future research directions and their potential for commercial adoption. Nanochannel sensors with novel structures, properties, and functional porous materials may lead to new trends in biomedical applications, including self-powered and wearable sensors for disease monitoring. We believe that this Account holds implications for promoting interdisciplinary endeavors encompassing chemistry and materials science and nanotechnology as well as analysis, biosensing, and biomedical science.

Hybrid Inclusion Materials Based on Chiral Nematic Mesoporous Organosilica with Incorporated Cyclodextrin Receptors

The creation of multicomponent materials with desired properties and functions is a challenge of modern materials chemistry. Chiral nematic mesoporous organosilicas have iridescent properties that make them attractive for decoration and sensing. In this paper, we demonstrate the chemical functionalization of chiral nematic mesoporous organosilica films with cyclodextrin. In this way, we have been able to create chiral nematic mesoporous films with macrocyclic molecules on the surface to obtain a new class of hybrid inclusion materials.

Dual Ionic Signal Detection: Modulation of Surface Charge of Nanofluidic Iontronics by Dual-Split Gate Voltages

Nanofluidic iontronics, including the field-effect ionic diode (FE-ID) and field-effect ionic transistor (FE-IT), represent emerging nanofluidic logic devices that have been employed in sensitive analyses. Making analyte recognitions in predefined nanofluidic devices has been verified to improve the sensitivity and selectivity using a single ionic signal, such as ionic current amplification, rectification, and Coulomb blockade. However, the detection of analytes in complex systems generally necessitates more diverse signals beyond just ionic currents. Here, we demonstrated that dual ionic signals, steady ionic switching ratio, and transient response time (ts) act as detection signals modulated by dual-split gate voltages along the nanochannel for the detection of charged analytes. With an increase in gate voltage, the switching ratio decreases in both FE-ID and FE-IT, whereas the response time exhibits an exponential increase specifically in the FE-ID. Moreover, the response time shows no significant correlation with the external transmembrane voltage in the FE-IT. These results contribute to the optimization of reconfigurable iontronics through gate voltage modulation, providing a theoretical foundation for multiple ionic signal detection.