Larger picture in minipage, [scale=..] not effective [closed]

Question

I try to make the last picture in this minipage larger with the [scale=..] code, but it is not working. I hope it does not have to do with the original view of the picture, so it can be fixed using a latex code.

Here is how i coded in the latex file:

\begin{figure}[h]  
\begin{minipage}{.3\textwidth}  
  \includegraphics[width=\linewidth]{PEO.JPEG}  
  \small\caption{PEO}  
  \label{PEO}  
\end{minipage}%  
\begin{minipage}{.3\textwidth}  
  \centering  
  \includegraphics[width=\linewidth]{PCL.JPEG}  
  \caption{PCL}  
  \label{PCL}  
\end{minipage}%  
\begin{minipage}{.3\textwidth}  
  \centering  
  \includegraphics[scale=1.5][width=\linewidth]{polymersomePEOPCL.JPEG}  
  \bigskip   
  \caption{Polymersome of block co-polymer PEO-PCL}  
  \label{PEO-PCL}    
\end{minipage}    
\end{figure}%     

And this looks like this in the PDF file. Not very nice, because of the smaller last picture.

Thanks for the help!