## 1 Introduction  
Conjugated polymers have drawn considerable attention due to their great number of applications in different disciplines such as light-emitting diodes (LEDs) and luminescent solar cells, as well as their low cost and facile synthesis [1; 2; 3; 4; 5]. Among conjugated polymers, the poly(phenylene vinylene) (PPV) group has fascinated researchers due to its novel optical and electrical features [6; 7; 8; 9; 10; 11]. Conjugated polymers have been foreseen as potential radiation-sensing materials [12; 13; 14]. Conjugated polymers can be stimulated by injecting charges or utilizing photo-excitation. Optically active organic dyes, such as laser dyes, have spectral features similar to these macromolecules. However, many fluorescent organic compounds, including laser dyes, have a low fluorescence quantum yield under high concentrations due to reabsorption processes, and cannot emit laser light [15]. At variance, the PPV conjugated polymers have a strong absorption and emission, a significant Stokes shift, a high luminescence, and a fluorescence quantum yield, and emit laser light even at higher concentrations. In 1992, researchers discovered that a liquid conjugated polymer (MEH-PPV) produced yellow/red wavelengths that generated laser action.  
Furthermore, the efficiency of MEH-PPV was comparable to that of the conventional laser dye rhodamine 6G [16]. The spectral properties of B-co-MP were studied in a few organic solvents. The fluorescence spectrum of B-co-MP for low concentrations showed one peak at 535 nm. The intensity decreased by increasing the concentration and the spectrum's peak position red-shifted towards and became fixed at 580 nm [17; 18]. Under laser pump excitation (Nd: YAG (355 nm)), B-co-MP exhibits an amplified spontaneous emission (ASE) spectrum at 560 nm. This peak may be related to the monomeric state of MEH- PPV as a segment [19].  
On the other hand, the ionizing radiation technique is widely used to induce changes in structural and optical properties of polymers subjected to irradiation [20]. According to the experimental findings, ionizing radiation may induce a cross-link or break in polymers' molecular bonds based on the polymer structure, type of ionizing radiation, and absorbed dose [21,22]. Therefore, investigating the impact of radiation on these polymers is highly needed, which can be potentially exploited in diverse fields. For instance, [PERSON] et al. reported that the optical and electrical properties of poly allyl diglycol carbonate (CR-39) were enhanced upon gamma irradiation in the dose range of up to nearly 1 MGy [23]. In a previous study, gamma irradiation influenced both films and solutions in the chloroform of poly[2-methoxy-5-(2\({}^{\prime}\)-hexyloxy)-p-phenylenevinylene] (MEH-PPV). MEH-PPV in solution was sensitive to low doses of ionizing radiation. Recently, polypyrrole and polyvinylpyrrolidone hydrogels with varying concentrations and content were irradiated with gamma rays at 25 kGy to facilitate polymerization and cross-linking, resulting in PPy/PVP hydrogels with optimal mechanical properties [24]. This work attempts to provide a deeper insight into the optical properties of the conjugated copolymer of B-co-MP in tetrahydrofuran (THF) as a function of concentrations and irradiation doses. We highlight that the spectral profiles of B-co-MP and ASE wavelengths change remarkably upon varying the \(\gamma\)-irradiation dose. The low-cost, easy preparation, and the proper dosimetric response of B-co-MP render it an effective tool for biomedical applications.