Controller.php

<?php 

/**
     * Insert a new permission(s).
     *
     * @url    POST: /permissions/insert
     * @param  Requests\PermissionValidator $input
     * @return \Illuminate\Http\RedirectResponse
     */
    public function insertPermission(Requests\PermissionValidator $input)
    {
        if (Permissions::create($input->except('_token'))) {
            $roles = User::whereIs('admin')->get();

            $user  = auth()->user();
            $user->notify(new InsertPermission());
        }

        session()->flash('Message', 'Permission has been added');
        return redirect()->back();
    }

error.txt

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'read_at' in 'field list' (SQL: insert into `notifications` (`id`, `type`, `data`, `read_at`, `notifiable_id`, `notifiable_type`, `updated_at`, `created_at`) values (071abbf4-13bc-4699-8f03-9c455f2dd966, App\Notifications\InsertPermission, {"employee_id":9,"message":"has inserted a new permission"}, , 9, App\User, 2016-08-20 01:39:39, 2016-08-20 01:39:39))

InsertPermission.php

<?php

namespace App\Notifications;

use Illuminate\Bus\Queueable;
use Illuminate\Notifications\Notification;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Notifications\Messages\MailMessage;

class InsertPermission extends Notification
{
    use Queueable;

    /**
     * Create a new notification instance.
     *
     * @return void
     */
    public function __construct()
    {
        //
    }

    /**
     * Get the notification's delivery channels.
     *
     * @param  mixed  $notifiable
     * @return array
     */
    public function via($notifiable)
    {
        return ['database'];
    }

    /**
     * Get the array representation of the notification.
     *
     * @param  mixed  $notifiable
     * @return array
     */
    public function toArray($notifiable)
    {
        return [
            'employee_id' => auth()->user()->id,
            'message'     => 'has inserted a new permission'
        ];
    }
}