Send readings of Wireless temperature sensor using JSON object through particle photon

How to send JSON objects to a firebase real-time database?
I want to send the wireless temperature sensor data received by a gateway receiver connected serially via Particle photon, is it possible to send the data by using POST method in JSON any suggestion will be a great help.

Yes, that should be possible. There should also already be a couple of tutorials out there doing something similar. Give the search function a shot, and also have a look at webhooks.