# Downsizing Mo6I12 to Nanocrystals Unveils Visible-Light Photocatalytic Antibacterial Activity

## TL;DR

Researchers found that nanocrystals made from Mo6I12 can kill bacteria using visible light, making them useful for water disinfection.

## Contribution

The study demonstrates the photocatalytic antibacterial activity of Mo6I12 nanocrystals under visible light for the first time.

## Key findings

- Mo6I12 nanocrystals show visible-light absorption up to 700 nm and photoluminescence.
- The nanocrystals generate reactive oxygen species under blue light, even in anaerobic conditions.
- They effectively inactivate Gram-positive bacteria with over 4 log reduction under visible light.

## Abstract

Molybdenum­(II) iodide (Mo6I12)
serves as
a versatile precursor to phosphorescent octahedral molybdenum cluster
complexes that exhibit properties relevant to energy, environmental,
and biomedical applications. Despite its straightforward synthesis,
stability, and extended visible-light absorption, the photophysical
and photocatalytic properties of Mo6I12 have
remained unexplored, because the compound has historically been available
only as an insoluble bulk material. Herein, we report the top-down
preparation of Mo6I12 nanocrystals via ultrasonic
treatment, yielding stable colloidal suspensions in acetone and water.
The nanocrystals exhibited broad visible-light absorption extending
up to ∼700 nm and weak red to near-infrared photoluminescence
intensifying at low temperatures. These features indicate an indirect
semiconducting nature, which was confirmed by density functional calculations.
Upon blue-light illumination, the nanocrystals generate reactive oxygen
species, including the hydroxyl radical via a photocatalytic mechanism
that operates even under anaerobic conditions. Their photocatalytic
potential in the context of water disinfection was validated through
bacterial photodynamic inactivation, demonstrating effective inactivation
(up to >4 log reduction) of clinically relevant strains of Gram-positive
bacteria under visible-light irradiation. The low toxicity of the
nanocrystals on HeLa cells highlighted their favorable safety profile
for water disinfection. This work reveals the unique light-induced
properties of Mo6I12 nanocrystals and establishes
them as promising materials for photocatalytic and photodynamic applications.