Abstract Deep eutectic solvents (DES) are emerging as promising sustainable antimicrobial systems owing to their tuneable physicochemical properties and biocompatibility. This study reports the first synthesis and physicochemical characterisation of a series of Tris(hydroxymethyl)aminomethane (Tris)-based DES, prepared with acidic, neutral, and basic hydrogen bond donors via microwave-assisted and conventional thermal methods in quantitative yield. All formulations were characterised by FTIR spectroscopy, differential scanning calorimetry (DSC), and rheological measurements. Acid-based DES exhibited true eutectic melting behaviour with transition enthalpies of 63–81 J/g and sub-ambient melting points, while polyol- and urea-based systems displayed glass-transition-dominated profiles with markedly lower enthalpies (3.5–10.6 J/g). Viscosities at 25 °C ranged from 12.0 to 528.5 mPa.s, with acid-based formulations showing intermediate values most suitable for antimicrobial application. Antimicrobial evaluation against Pseudomonas fluorescens and Staphylococcus epidermidis demonstrated that DES-2 (Tris: citric acid: water) and DES-3 (Tris: formic acid: water) were the most active formulations, with MIC values of 2–4% (v/v) against both strains, while survival assays showed DES-2 reduced P. fluorescens viability to 31.0% ± 6.0% and S. epidermidis to 8.3% ± 5.8% relative to untreated controls ( p < 0.001). Comparison with individual parent components confirmed that antibacterial activity is enhanced within the eutectic structure, demonstrating that antimicrobial efficacy is governed by formulation-dependent physicochemical properties rather than acidity alone.
Chakraborty et al. (Mon,) studied this question.