Dielectric Relaxation Spectroscopy Dataset for Aqueous Methylene Blue Solutions (200 MHz–20 GHz, 293.15–323.15 K)

This dataset contains vector network analyzer (VNA) broadband dielectric relaxation spectroscopy measurements of aqueous methylene blue (MB) / distilled water (DW) solutions over 200 MHz–20 GHz, at four temperatures (293.15, 303.15, 313.15, and 323.15 K) and eleven MB concentrations (0–0.0100 weight fraction), comprising 44 physically distinct spectra. Data are provided as four Excel workbooks, one per temperature. Each workbook contains six sheets reporting, as a function of frequency and concentration: real permittivity (ε′, sheet E1), dielectric loss (ε″, sheet E2), AC conductivity (σ_ac), loss tangent (tan δ), and the real and imaginary components of the complex electric modulus (M′, M″). This dataset supports the manuscript "Physics-Informed and Uncertainty-Aware Machine Learning for Multi-Property Prediction and Inverse Design of Dielectric Relaxation Behaviour in Aqueous Methylene Blue Solutions.