what is wrong with my code

t=86400;
v=10.^-5;
D=10.^-7;
x=0:0.01:2;
%Calcuate the concentration in ( mol/l)
conc=(1./sqrt(4*pi*D*t)*exp.(-1*((x-v*t).^2./4*D)));

Errors:

Argument to dynamic structure reference must evaluate to a valid field name.

Error in CES_StudentID_empty (line 54)

conc=(1./sqrt(4*pi*D*t)*exp.(-1*((x-v*t).^2./4*D)));

[Walter Roberson]

Duplicates https://www.mathworks.com/matlabcentral/answers/816205-what-is-wrong-with-my-code?s_tid=srchtitle