Polycaprolactone and polycaprolactone/chitosan nanofibres functionalised with the pH-sensitive dye Nitrazine Yellow

► pH-sensitive PCL and PCL/chitosan nanofibres are successfully electrospun. ► pH-sensitive PCL and PCL/chitosan nanofibres show a clear halochromic response. ► Chitosan addition results in a significantly increased water sorption. ► Chitosan addition is indispensable for a sensitive and rapid response. ► Theoretical modelling on the dye-polymer interactions underpins the experimental findings.