Anomalous enhancement of nanodiamond luminescence upon heating

TL;DR

This study reveals that nanodiamond photoluminescence significantly increases upon heating due to water desorption from their surfaces, contrasting with bulk diamond behavior.

Contribution

It demonstrates an anomalous luminescence enhancement in nanodiamonds caused by surface water removal at elevated temperatures.

Findings

Nanodiamond PL increases by nearly tenfold upon heating to 200-250°C.

Water adsorbed on ND surfaces quenches PL, and its desorption enhances luminescence.

The effect is consistent across nanodiamonds of different origins.

Abstract

Characteristic photoluminescence (PL) of nanodiamonds (ND) of very different origin (detonation, HPHT, extracted from meteorite) was studied in situ at high temperatures in the range 20-450C. Luminescence was excited using 473 nm laser and recorded in the range 500-800 nm. In contrast to decrease of point defect PL in bulk diamond with temperature, we found that the nanodiamond luminescence related to ND surface defects increases almost an order of magnitude upon heating to 200-250 C. The observed effect reveals that water adsorbed on ND surfaces efficiently quenches photoluminescence, water desorption on heating leads to dramatic increase of the radiative de-excitation.