From Structure to Biology: A Holistic Analysis of Shock Wave-Modified 4-Methylbenzoic acid (4MBA) Crystals

Controlled manipulation of molecular crystals under external stimuli represents an efficient method to optimize multiple functionalities in organic systems. In this study, 4-methylbenzoic acid (4MBA) single crystals have been synthesized and investigated prior and post shock wave loading of Mach 1.3. Shock wave loading was conducted in a lab-scale shock tube capable of generating high-pressure pulse of 2.5 ms duration occurring every 2 seconds. Crystalline structure, optics, conductivity, mechanical behaviour, nonlinear optical performance, and biological activity were characterized by means of single crystal and powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Visible spectroscopy (UV-Vis), refractive index dispersion measurement, photoconductivity tests, Urbach energy determination, scanning electron microscopy (SEM), photoelasticity analysis, and Z-scan measurements. Biological investigation of the crystals involved in vitro antibacterial and antifungal activity as well as evaluation of cytotoxic effect against Human Hepatocellular Carcinoma Cell Line G2 (HepG2). The results demonstrated shock-induced lattice distortion, decreased unit cell volume, increased crystallinity, changed optical absorbance, improved photoconductivity response, and better nonlinear optical behaviour of crystals. Enhanced antimicrobial and anticancer activities have been detected following shock wave treatment. The current study is the first to systematically examine shock wave-induced 4MBA single crystals and proves that shock wave tuning is an effective way to improve structural, optoelectronic, NLO, and biological properties at once. The obtained results show that 4MBA is a good candidate to be used in the next-generation photonics and biotechnology devices.