This study investigates the effect of uniaxial tensile strain (0–2.2%) on the phonon spectra and band structures of monolayer and bilayer molybdenum disulfide (MoS₂). Using Raman spectroscopy, the researchers observed phonon softening and a splitting of the E' Raman mode, extracting a Grüneisen parameter of ~1.06. Photoluminescence (PL) spectroscopy revealed a linear decrease in the optical band gap with strain, with monolayer MoS₂ showing a reduction of ~45 meV/% and bilayer MoS₂ ~120 meV/%. A significant decrease in PL intensity for monolayer MoS₂ was observed, indicating a transition from a direct to an indirect band gap at ~1% strain. First-principles calculations confirmed this transition, showing the optical band gap becomes indirect at ~1% strain while the fundamental band gap remains direct. The study demonstrates that strain engineering can modulate the band structure of two-dimensional materials like MoS₂, enabling control over electronic and optical properties. This has potential applications in tunable photonic devices, solar cells, and nanoscale stress sensors. The results highlight the importance of strain in manipulating the electronic and optical behavior of MoS₂, offering new avenues for exploring its properties and applications in two-dimensional materials. The findings support the use of strain engineering as a powerful tool for both fundamental research and practical device applications in transition-metal dichalcogenides.This study investigates the effect of uniaxial tensile strain (0–2.2%) on the phonon spectra and band structures of monolayer and bilayer molybdenum disulfide (MoS₂). Using Raman spectroscopy, the researchers observed phonon softening and a splitting of the E' Raman mode, extracting a Grüneisen parameter of ~1.06. Photoluminescence (PL) spectroscopy revealed a linear decrease in the optical band gap with strain, with monolayer MoS₂ showing a reduction of ~45 meV/% and bilayer MoS₂ ~120 meV/%. A significant decrease in PL intensity for monolayer MoS₂ was observed, indicating a transition from a direct to an indirect band gap at ~1% strain. First-principles calculations confirmed this transition, showing the optical band gap becomes indirect at ~1% strain while the fundamental band gap remains direct. The study demonstrates that strain engineering can modulate the band structure of two-dimensional materials like MoS₂, enabling control over electronic and optical properties. This has potential applications in tunable photonic devices, solar cells, and nanoscale stress sensors. The results highlight the importance of strain in manipulating the electronic and optical behavior of MoS₂, offering new avenues for exploring its properties and applications in two-dimensional materials. The findings support the use of strain engineering as a powerful tool for both fundamental research and practical device applications in transition-metal dichalcogenides.