# Atomically thin gold embedded in inkjet-printed PVA hydrogels: flexible catalysts for ambient phenol degradation

## TL;DR

Inkjet-printed gold nanotape hydrogels offer a reusable and efficient way to break down pollutants like phenol and 4-nitrophenol at room temperature.

## Contribution

The study introduces inkjet-printed gold nanotape hydrogels as a scalable, high-efficiency platform for ambient pollutant degradation.

## Key findings

- AuNTps show nearly twice the catalytic efficiency for 4-NP reduction compared to spherical AuNPs.
- Inkjet-printed AuNTp meshes achieve a fourfold increase in 4-NP reduction rate compared to drop-cast gels.
- Printed hydrogels degrade 26% of phenol in 4 hours at room temperature with consistent performance over multiple cycles.

## Abstract

Inkjet-printed gold nanotape (AuNTp) structures embedded in polyvinyl alcohol (PVA) hydrogels provide a reusable, high-surface-area platform for catalytic degradation of phenol and 4-nitrophenol (4-NP) under ambient conditions. AuNTps, featuring distinct three-dimensional “heads” and atomically thin quasi-one-dimensional “tails”, enhanced catalytic activity in both reduction and oxidation reactions. Compared to spherical gold nanoparticles (AuNPs), AuNTps are nearly twice as catalytically efficient for 4-NP reduction on a per-mass basis, reflecting the influence of anisotropic morphology on surface-sensitive electron transfer. In contrast, phenol oxidation shows weaker morphology dependence, likely proceeding through hydroxyl radical-mediated pathways that are less sensitive to catalyst shape or facet structure. To enable rapid substrate diffusion and facilitate reuse, AuNTps were formulated into PVA inks and inkjet-printed into micrometre-thick hydrogel mesh architectures (8 to 15 µm thick). Although printed meshes show reduced activity relative to free AuNTps in solution, they achieve a nearly fourfold increase in mass-normalised rate constants for 4-NP reduction compared to drop-cast gels (0.24 × 104vs. 0.07 × 104 min−1 g−1) and achieve 26% phenol, a common water pollutant, in 4 hours at room temperature, with consistent performance over multiple cycles. These findings demonstrate the potential of inkjet-printed nanozyme hydrogels as scalable, heterogeneous catalysts. Further improvements may be achieved by optimising catalyst-matrix interactions to reduce diffusion and accessibility barriers. This work addresses a significant challenge in nanozyme catalysis: translating high-performance nanomaterials into practical, reusable formats suitable for environmental remediation.

Printable PVA hydrogels embedded with gold nanotapes enable reusable, high-efficiency catalysts for pollutant degradation at room temperature. Inkjet-printed meshes boost diffusion, achieving 4× faster 4-NP reduction than bulk gels.