How to push strings (char by char) into a vector of strings

This code is just a prototype, how I'm expecting my output..
My program should be able to insert char by char to particular index of vector;

This program works fine for vector<vector<int>>

#include<bits/stdc++.h>

using namespace std;

int main()
{
  
  vector<vector<string>>v;

  for(auto i=0;i<5;i++)
  v.emplace_back(vector<string>());
  
  v[0].emplace_back('z');
  v[1].emplace_back('r');
  v[0].emplace_back('x');
  v[1].emplace_back('g');
  
  for(auto i:v){
  for(auto j:i)
  cout<<j<<" ";cout<<endl;}
  
  
  return 0;
}

My Expected output:
z x
r g

Error:
no matching function for call to ‘std::__cxx11::basic_string<char>::basic_string(char)’ { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }