# High-Pressure High-Temperature Nanodiamond-Modified ZnO Nanocomposites as Promising Photocatalysts: Synthesis and Characterization

## TL;DR

Scientists made a new type of photocatalyst using nanodiamonds and zinc oxide, which is more efficient and stable for cleaning water.

## Contribution

HPHT nanodiamonds are shown to significantly improve ZnO photocatalytic efficiency by reducing defects and enhancing charge separation.

## Key findings

- ND–ZnO 10 (ND:ZnO = 0.1 w/w) achieves threefold higher photocatalytic efficiency than pure ZnO.
- HPHT NDs reduce defects and improve charge-carrier separation in ZnO composites.
- ND–ZnO 10 retains 88% efficiency after five reuse cycles, showing durability for water treatment.

## Abstract

What are the main findings?
HPHT nanodiamonds enhance the performance of ZnO-based photocatalysts.Optimal ND:ZnO ratios suppress defects and improve charge-carrier separation.ND–ZnO 10 (ND:ZnO = 0.1 w/w) achieves threefold-higher photocatalytic efficiency compared to pristine ZnO.

HPHT nanodiamonds enhance the performance of ZnO-based photocatalysts.

Optimal ND:ZnO ratios suppress defects and improve charge-carrier separation.

ND–ZnO 10 (ND:ZnO = 0.1 w/w) achieves threefold-higher photocatalytic efficiency compared to pristine ZnO.

What are the implications of the main findings?
HPHT ND–ZnO composites open new directions for defect engineering in photocatalysis.HPHT ND–ZnO systems provide promising photocatalysts for environmental remediation.ND–ZnO 10 shows stable reuse, confirming its potential for water-treatment applications.

HPHT ND–ZnO composites open new directions for defect engineering in photocatalysis.

HPHT ND–ZnO systems provide promising photocatalysts for environmental remediation.

ND–ZnO 10 shows stable reuse, confirming its potential for water-treatment applications.

Zinc oxide (ZnO) nanostructures suffer from fast electron–hole recombination, limiting their applicability in photocatalytic environmental remediation, and carbon additives such as detonation nanodiamonds (DNDs) are constrained by their high defect density. To address this, ZnO nanocomposites modified with high-pressure, high-temperature nanodiamonds (HPHT NDs) were synthesized to evaluate whether their intrinsically lower defect density—evidenced by a dominant diamond Raman peak at 1330 cm−1 and a low sp2 carbon fraction of 6.6% compared to oxidized DNDs with strong D/G bands (~1350/1580 cm−1) and ~25–35% sp2 carbon—can enhance charge separation and improve photocatalytic activity. Oxidized HPHT NDs bearing carbonyl, carboxyl, and hydroxyl groups enabled covalent attachment to ZnO, and the resulting ND–ZnO composites were characterized by SEM/EDX, ATR-FTIR, Raman spectroscopy, XPS, and cathodoluminescence (CL). EDX confirmed increasing carbon incorporation from 13.0 to 52.9 at.%, while XPS revealed a 0.5 eV shift in the Zn 2p3/2 peak and an increase in Zn–O–Zn lattice oxygen from 31.3% to 61.6% in ND–ZnO 10. CL showed enhanced near-band-edge emission and reduced Zni-related luminescence (~3.0 eV). ND–ZnO 10 achieved a nearly threefold-higher degradation rate constant (0.0251 min−1) than pristine ZnO (0.0087 min−1) and retained 88% efficiency after five cycles, demonstrating strong potential for durable wastewater treatment.