# UV–Vis Detection of Thioacetamide: Balancing the Performances of a Mn(III)-Porphyrin, Gold Colloid, and Their Complex for Selecting the Most Sensitive Material

## TL;DR

This study compares different materials for detecting thioacetamide, finding that a complex of a porphyrin and gold nanoparticles offers the highest sensitivity.

## Contribution

The study introduces a novel complex of Mn(III)-porphyrin and gold nanoparticles for enhanced thioacetamide detection sensitivity.

## Key findings

- Mn-3,4-diMeOPP detects thioacetamide in a linear range of 3.13 × 10−8 M–7.67 × 10−7 M.
- The Mn-3,4-diMeOPP–AuNPs complex detects thioacetamide in a trace domain of 1.99 × 10−8 M–1.76 × 10−7 M.
- The complex's detection mechanism involves electrostatic interactions between the porphyrin and thioacetamide.

## Abstract

The optical detection of thioacetamide was investigated using a metalated porphyrin, Mn(III)-5,10,15,20-tetrakis-(3,4-dimethoxyphenyl)-21H,23H-porphyrin chloride (Mn-3,4-diMeOPP), a gold colloid solution (AuNPs), and a complex formed between them (Mn-3,4-diMeOPP–AuNPs) in order to select the most sensitive material and to achieve complementarity between methods. Mn-3,4-diMeOPP, AuNPs, and their complex were synthesized and characterized by means of UV–Vis, FT-IR spectrometry, and AFM investigations. It could be concluded that Mn-3,4-diMeOPP could detect/quantify thioacetamide (TAA) in the range 3.13 × 10−8 M–7.67 × 10−7 M in a linear fashion, with a 99.85% confidence coefficient. The gold colloidal particles alone could detect TAA in an extremely narrow concentration domain of 2–9.8 × 10−7 M, slightly complementary with that of Mn-3,4-diMeOPP. The complex between Mn-3,4-diMeOPP and gold colloid proved to be able to quantify TAA in the trace domain with concentrations of 1.99 × 10−8 M–1.76 × 10−7 M in a polynomial fashion, with the method being more difficult. A potential mechanism for TAA detection based on Mn-3,4-diMeOPP is discussed based on computational modeling. The distorted porphyrin conformation and its electronic configuration favor the generation of a grid of electrostatic interactions between porphyrin and TAA.