Search Query by removing casesensetive in angularFire2?

Question

this.userData = this.af.database.list('/REPORTS',{
    query: {
      orderByChild: 'siteName',
      startAt: val,
      endAt:val+'\uf8ff' 
    }
});

Firebase returns data only when I'm giving first letter is in capital. But when I'm giving first letter as lowercase its returning null. I want that firebase should return the data on both condition either first letter is uppercase or lowercase.