When the reaction is conducted with cGO, a darker hydrogel is obtained. Similar to graphene, GO is highly transparent in the visible spectrum, the degree of transparency being attributed to electrostatic, chemical, van der Waals interactions and others that, remain largely unknown. However, the transparency of graphene oxide decreases as a function of its number of layers. Therefore, these new alginate composites are much darker because they have folded 3D GO networks instead of uncrosslinked GO sheets. In addition, cGO/Alg is much more consistent as observed by the differential scanning calorimetry (DSC) measurements that show a more homogeneous behaviour with less crystallisation peaks on heating starting at higher temperature (Fig 5C followed by a melting peak related to thermal degradation of the alginate at a higher temperature. Besides, its chemical structure seems to be much better linked after immersion in distilled water for 3 hours at room temperature (24±1°C) (Fig 5E). Hence, bonds between GO nanosheets and alginate chains occur via divalent calcium atoms in both GO/Alg and cGO/Alg. However, continuous crosslinked GO nanosheets linked to the alginate polymer matrix through these bonds produce a higher reinforcement as expected (Fig 6). In this Fig 6, the storage modulus (E′) and loss tangent (tan δ) are investigated by dynamic mechanical analysis (DMA) to determine the performance of these two composite materials under stress at various temperatures. For both samples, a decrease in storage modulus (E’) is observed as the temperature increases because the material undergoes a glass/rubber transition state. It is also noticed that the incorporation of crosslinked GO into the alginate matrix (sample cGO/Alg) leads to a considerable increase in the storage modulus (E’) as compared with the addition of single GO sheets (sample GO/Alg). The raise in the storage modulus is due to the higher reinforcing effect of the irregular graphene oxide tubes and higher interfacial interaction between these tubular carbon materials and alginate that restricts more the mobility of polymer chains at Alginate-cGO interface and high modulus of cGO. The damping factor (tan δ) exhibits a single dynamic mechanical relaxations in cGO/Alg in contrast to the heterogeneous behaviour of GO/Alg with two mechanical relaxations in good agreement with the DSC results.