# Antimicrobial and Photocatalytic Properties under Visible Blue LED Light of Silver Phosphate Supported on Biogenic Zeolite from Amazon Natural Source

## TL;DR

This study creates a new hybrid material using silver phosphate and Amazonian zeolite, which shows strong antimicrobial and photocatalytic properties under visible light.

## Contribution

The novel contribution is the synthesis and characterization of silver phosphate supported on biogenic Amazonian zeolite with enhanced photocatalytic and antimicrobial performance.

## Key findings

- AgP_ZLT_95 achieved 97.07% RhB dye discoloration under visible light, showing high photocatalytic efficiency.
- The hybrid materials exhibited strong antimicrobial activity with MIC values as low as 0.01562 mg/mL for bacteria.
- Zeolite reduced photocorrosion of silver phosphate and enhanced the generation of reactive oxygen species.

## Abstract

In this study, we report the synthesis of silver phosphate
supported
on a phase mixture of Analcime and Pitiglianoite zeolites. The hybrid
materials were obtained with AgP amounts of 25% (AgP_ZLT_25), 50%
(AgP_ZLT_50), 75% (AgP_ZLT_75), and 95% (AgP_ZLT_95) relative to the
ZLT mass. Structural characterization by X-ray diffraction (XRD) and
structural refinement by the Rietveld method revealed that ZLT is
composed of 71.02 ± 0.54% Analcime and 28.98 ± 0.47% Pitiglianoite
zeolite. The percentage of AgP in the mixture, also quantified by
the Rietveld method, resulted in values of 7.99 ± 0.46, 36.70
± 4.84, 67.50 ± 5.06, and 93.74 ± 3.15% for the samples
AgP_ZLT_25, AgP_ZLT_50, AgP_ZLT_75, and AgP_ZLT_95, respectively.
Vibrational characterization by Raman and infrared (IR) spectroscopy
revealed the presence of the main active vibrational modes of silver
phosphate, silicate, and aluminate groups, in both pure and hybrid
materials. The E
gap values revealed that
ZLT effectively absorbs in the ultraviolet region, with E
gap equal to 3.65 eV. While the hybrid materials exhibited
a decrease in the E
gap value, specifically
between 3.63 eV (AgP_ZLT_25) and 2.35 eV (AgP_ZLT_95), in consequence
of the contributions of the electronic transitions of AgP (E
gap = 2.35 eV). The photocatalytic performance
of the materials prepared in the photodegradation of RhB dye in an
aqueous medium under exposure to LED-simulated visible light resulted
in dye discoloration percentages of 97.07% for the AgP_ZLT_95 sample
and 93.56% for the AgP_ZLT_75 sample. Furthermore, analysis of the
rate constant (k
app) and half-life of
the reactions (t
1/2) revealed that the
AgP_ZLT_95 catalyst was approximately 1,391.5 times more efficient
compared to photolysis, exhibiting superior activity in the generation
of superoxide radicals and vacancies. Additionally, it was found that
zeolite acts as a sacrificial material, reducing the photocorrosion
process of silver phosphate. Hybrid materials, as well as AgP, exhibited
high antimicrobial activity, resulting in a minimum inhibitory concentration
(MIC) of 0.01562 mg mL–1 for the bacteria Staphylococcus aureus and Escherichia
coli, while for the fungi Candida parapsilosis and Candida albicans, the MIC was
0.03125 mg mL–1, as a result of redox processes
involving reactive oxygen species (ROS), as well as silver-ion activity
and [AgO4] and [PO4] clusters in the cell wall
and internal structures of microorganisms.