UV LED Technology
Source: | Author:Sandy Qing | Published time: 2019-12-31 | 3007 Views | Share:
What's UV?


                   The following is intended as a valuable introduction to UV(ultraviolet) for newcomers and enthusiasts alike.

                   Ultraviolet light is that portion of the electromagnetic spectrum that lies beyond the purple edge of the visible

                   spectrum and has wavelengths between 100 and 400 nm. The UV spectrum is further divided into ranges as follows.



                                                                       Range Name                                              Wavelength Range / nm 

                                                                           UVA                                                                 315 - 400

                                                                           UVB                                                                  280 - 315

                                                                           UVC                                                                  200 - 280 

                                                                      Vacuum UV                                                           100 - 200



                    The UVA range causes sun tanning in the human skin. The UVB range causes sun burning. The UVC range is absorbed by DNA and

                    thus can cause cancer and mutations. This is also the range that is most effective in inactivating bacteria and viruses. The Vacuum UV

                    range is absorbed strongly by water and air and thus can only be transmitted in a vacuum.


                    Ultraviolet photons are particularly energetic and when absorbed in molecules can cause bonds to be broken ( photo-chemistry).

What's a "photon"?



                     Ultraviolet light (along with all others forms of electromagnetic radiation) comes in discrete energy packets called "photons". The

                     energy of a photon is given by

U = hn = hc/l



                     Where h is the Planck constant (6.626755 x 10 - 34 J s), c is the speed of light ( 2.997925 x 108 ms - 1 ), n is the frequency (Hz) of the

                     light, l is the wave number ( cm -1 or m - 1 ) of the light and l is the wavelength (nm or m). Usually photochemical "event" involve

                    absorption of only one photon per molecule.




Why is UV important for the disinfection of water and air?



                  The portion of the UV spectrum (The germicidal region) that is important for disinfection of water and air, is the range that is absorbed

                  by DNA (RNA in some viruses). This germicidal range is approximately 200 - 300 nm, with a peak germicidal effectiveness at about

                  260nm. The mechanism involves absorption of a UV photon by pyrimidine bases (principally thymine) where two pyrimidine bases

                  are next to each other on the DNA chain. The photochemistry involves formation of a dimera that links two bases together. This causes

                  a disruption in the DNA chain, such that when the cells undergoes mitosis (cell division), the replication of DNA is inhibited.




What are the major commercial applications of UV?



                  UV has many commercial applications in society. The major ones are: UV disinfection of water and air, UV Curing of inks and coatings, 

                  UV disinfection of foods, UV-based Advanced Oxidation destruction of pollutants of water and air.



What's "Advanced Oxidation"?



                 Advanced oxidation describes processes that induce accelerated oxidation of organic pollutants in water and air. When carried to

                 completion, The only products are water, carbon dioxide and mineral acids from any chlorine, nitrogen or sulfur present. This process

                 is called "mineralization". Advanced Oxidation Technologies (AOTs) come in many varieties and usually involve the generation of

                 "hydroxyl" (OH) radicals, which attack and oxidaize the organic contaminants. UV-based AOTs usually involve the generation of OH

                 radicals by the photolysis of hydrogen peroxide (H2O2).