Explosion before destroying

Firstly you need to import the package.

1. Go to the Assets

2. Click on import Package Particles.

This is some code I wrote it may be able to help you.

using UnityEngine; using System.Collections;

public class Trap : MonoBehaviour {

 //public ParticleEmitter PE_BlastBomb;
 public ParticleEmitter PE_EnemyExplosionEffect;
 public ParticleEmitter PE_BlastBomb;
 // Use this for initialization
 void Start () 
 {
 
 }
 
 // Update is called once per frame
 void Update () 
 {
     if(Input.GetKeyUp(KeyCode.E))
     {
         FireExplosion();
     }
 }
 public void FireExplosion()
 {
     ParticleEmitter PE_effect = (ParticleEmitter)Instantiate(PE_BlastBomb,transform.position,Quaternion.identity);
     PE_effect.Emit();
     
     Vector3 V3_explosionPos = transform.position;
     Collider[] C_collider = Physics.OverlapSphere(V3_explosionPos,10.0f);
     foreach(Collider C_hit in C_collider)
     {
         if(!C_hit)
         {
             continue;
         }
         if(C_hit.rigidbody)
         {
             C_hit.rigidbody.AddExplosionForce(300.0f,V3_explosionPos,10.0f);
         }
     }
     Destroy(gameObject);
 }

}

The simplest answer, conceptually, is to get a prefab of an explosion (I'm partial to the Detonator package on the asset store) and instantiate it just before destroying the cube.