Turner also put smiles on sick kids and attracted media attention when he dressed up as superhero Spider-Man to clean windows on the outside of a Tennessee children's hospital.

The 36-year-old Nashville resident, however, was hiding a depraved secret.

Turner is a pedophile with a lust for young boys and girls and was abusing children he babysat, took photos of his vile acts and shared the images online with other pedophiles.

Prosecutors said Jarratt dressed up as Spider-Man in an attempt to "access other vulnerable children" at the hospital, although there was no indication he was successful.

Turner's secret Nashville life was first exposed half a world away by undercover investigators from the Queensland Police Service's Task Force Argos, a world-leading pedophile hunting unit.

Task Force Argos started the Turner investigation in 2015.

The US legal system completed it on Monday.

US District Court Judge Marvin Aspen sentenced Turner to 105 years' jail in his Nashville courtroom on Monday.

"The sentence imposed by the court should insure that this defendant will never have another opportunity to inflict his perverted sexual desires upon another innocent child," said US Attorney for the Middle District of Tennessee Don Cochran said.

An undercover Queensland investigator first made online contact with Turner in May, 2015.

Turner emailed two images of a nude 2.5-year-old girl on a baby changing table to the officer.

In an email exchange Turner admitted sexually abusing the girl, that he had photos of a young boy and wrote, "I like boys and girls age 2-10."

Turner also created an account on a photo sharing website with one album containing photos titled "my little boy" and the other "my little girl".

"I loooooove little ones," he wrote.

The boy and girl were from two different families Turner befriended and babysat for.

He took sexually explicit images and videos of the toddler girl on 10 different occasions and of the infant boy on six different times in his basement apartment in Nashville.

Task Force Argos passed the information to US Homeland Security Investigations which led to a Nashville cafe.

Turner regularly visited the cafe and used its wireless internet to send the images.

The cafe's manager and staff helped identify Turner.

"The manager further stated that (Turner) would order the same thing, coffee and two scoops of ice cream, most of the time," the criminal complaint against Turner states.

Turner entered guilty pleas to 16 counts of production of child pornography and transportation of child pornography.

Australian Associated Press