Are the Nikon D3000 and D7000 capable of taking Infrared photography?

If there's any modification required I would like to know it please…

Both of those cameras have a filter in front of the sensor that blocks almost, but not all IR light. If you get an IR filter for your lens that will block visible light. You will then be able to get IR image with very long (several minute) exposures.

If you want to take IR photos at normal shutter speeds, you can have the sensor filters replaced with filters that allow visible light to pass through for around $400 from Lifepixel.com

Any DSLR is capable of infrared photography - two methods;

- you need an IR filter on the lens (something like the R72 or R95 which block wavelengths below 720nm and 950nm respectively) and a tripod because the exposures will be long (there's an IR filter over the sensor which blocks most of the IR, so you need long exposures to get enough to make an image).

- or you permanently have the IR filter in front of the sensor removed. This allows the camera to take IR pictures as 'normal' exposures, the trouble is you can't then use the camera for anything else. People who do IR & don't want to use filters/long exposure often buy a cheaper second had DSLR body & have it converted just for IR work.

I've put an R72 IR filter in front of my Nikon and shutter-speeds go down to a 1/30 to few seconds in bright daylight. Very doable though without mods on a tripod. You're only real problem is that you can't see a good image looking through the finder with the filter in place, that's all.