Electrospinning Machine | Sustained Metal Ion Release-Controlled Synthesis of Polyoxometalate Subnanowires

Subnanowires (SNWs) are one-dimensional materials with diameters approaching the unit cell scale (<1 nm), combining the functionality of inorganic materials and unique polymer-like properties such as flexibility, conformational diversity, and viscoelasticity due to structural similarities. They exhibit exceptional performance in polarized optical devices, information encryption, liquid transport, catalysis, and more. However, traditional synthesis methods rely on high-temperature and high-pressure conditions, resulting in low yield and hindering large-scale application.

Recently, Professor Zhang Simin’s team at the Beijing Institute of Technology published their latest research in Small Methods titled "Sustained Metal Ion Release-Controlled Synthesis of Polyoxometalate Subnanowires," with doctoral student Ma Rongzhu as the first author. The study employed a sustained metal ion release strategy to induce dynamic directional assembly of metal ions and polyoxometalates, successfully synthesizing silver ion-phosphomolybdic acid (Ag-PMA) SNWs under mild conditions (50°C, atmospheric pressure). 

Figure 1: Structure and composition of Ag-PMA SNWs.

The resulting Ag-PMA subnanowires are flexible, composed of nanoparticles with diameters of approximately 0.8 nm, and form stable self-supporting gels in good solvents like cyclohexane, demonstrating unique polymer-like properties.

Figure 2: Growth mechanism of Ag-PMA SNWs.

The dynamic growth process of Ag-PMA SNWs involving "disassembly-reassembly" is shown in Figure 2: PMA first self-assembles into subnanowires, then Ag+ adsorption disrupts the structure to form 2D sheets, which finally co-assemble with PMA into Ag-PMA subnanowires. Molecular dynamics simulations (Figures 2f-i) confirm the overall formation process. 

Figure 3: Universality of the synthesis method.

This synthesis method is universal, applicable to vanadium, manganese, iron, cobalt, copper, zinc, bismuth, chromium, nickel-based PMA SNWs, and even allows precise control of bimetallic/trimetallic SNWs. All metal SNWs exhibit ultra-thin diameters (<1 nm), ultra-high aspect ratios, and flexibility, spontaneously forming stable gels in non-polar solvents.

Figure 4: Spinnability of SNWs.

The polymer-like properties of SNWs break traditional limits, enabling polymer-free electrospinning of inorganic materials. Ag-PMA SNWs were directly spun into smooth fibers 3 μm in diameter with uniform element distribution and aligned internal SNWs, showing good mechanical properties. Other metal ion-PMA SNWs were also successfully spun into self-supporting fabrics, laying a technical foundation for inorganic functional textiles.

Figure 5: Photothermal conversion of Ag-PMA SNW fabrics.

Ag-PMA SNW fiber films exhibit excellent photothermal performance, heating from room temperature to 67.5°C within 100 seconds under one-sun intensity. By adjusting spinning processes, smart textiles like dresses, scarves, and gloves were made, rapidly heating under light. These textiles are lightweight (substrate-free), flexible, and efficient in energy conversion, offering new solutions for wearable photothermal devices.

Paper link: https://doi.org/10.1002/smtd.202500825