Understanding Ultraviolet LED Wavelength
What is ultraviolet wavelength?
The sun is a source of the full spectrum of ultraviolet radiation, which is commonly subdivided into UV-A, UV-B and UV-C. Wavelength, a fundamental descriptor of electromagnetic energy, is the distance between corresponding points of a propagated wave. Typical UV light source emission wavelengths range from ultraviolet (UV-C: 100 to 280nm; UV-B: 280 to 315nm; UV-A: 315 to 400nm) to visible light (400 to 700nm) and infrared (700 to 3000nm).
UV wavelengths typically are measured in nanometers (nm). Nanometer, a unit of length, is equal to one billionth of a meter. UV light-emitting diodes (LEDs) have a narrow spectral output centered on a specific wavelength, +/- 15nm, with typical commercial UV-LED lamps emitting at 365nm, 385nm, 395nm or 405nm wavelengths.
Irradiance, produced by UV-LED light sources, has increased consistently year over year because of advancements in both diode and lamp technology, and now is available at effective outputs higher than those offered by traditional UV lamp technologies. UV-LED lamp systems have enough power to conquer a wide range of applications and today are being introduced commercially and for residential applications.
Irradiance and energy density
Generally, the more photons absorbed, the more chemical reactions and the higher degree effect. (Note, however, that more is not always better!)
Energy density (slang term: dose) and irradiance (slang term: intensity) are two key parameters that help to characterize the conditions experienced under UVC, and provide two specific variables that can be monitored and tweaked to optimize the overall properties and performance.
-05/22/2016 Mike Higgins
UV-C Ultraviolet Light Technology
UV-C Ultraviolet Light Technology (UV-C) kills pathogens, with maximum bactericidal effect at a wavelength of 250 nm. Studies by Michelle M. Nerandzic, Curtis J. Donskey, Deverick J. Anderson, and the CDC Prevention Epicenters Program continue to validate this century-known fact.
A 2014 study by Jinadatha affirmed that pathogens neither build up a tolerance to UV-C effects nor develop mutations with UV-C resistance. The source of UV-C light (mercury, xenon, [LED]) is not important as long as the right UV-C wavelength light is delivered in the correct antimicrobial dosage (ie, time and distance).
UV-C devices were the preferred antimicrobial technology of the 1940s and 1950s until costs of sustaining the equipment safely and advances in tuberculosis medications led to a decline in popularity. Today, the rise of multi-drug-resistant bacteria creates a real need for more effective environmental disinfection, enabling a more prominent, renascent role for UV-C devices
Ultraviolet light C (light wavelength 200 nm to 290 nm) has been shown to kill cultures of antibiotic resistant strains of bacteria such as methicillin-resistant Staphylococcus aureus. To evaluate the ability of ultraviolet light C to reduce the amount and type of bacteria present in chronically infected ulcers, as well as to establish the test-retest reliability of the semi-quantitative swab technique, a prospective, one-group, pre-post treatment study was conducted among patients receiving treatment in several in- and outpatient facilities and nursing homes. Individuals with chronic ulcers exhibiting at least two signs of infection and critically colonized with bacteria (n = 22) received a single 180-second treatment using an ultraviolet light C lamp (wavelength = 254 nm) placed 1 inch from the wound bed.
Semi-quantitative swabs taken immediately before and after UVC treatment were used to assess changes in the bacterial bio-burden present within the wound bed. Results demonstrated excellent test-retest reliability of the semi-quantitative swab technique used to evaluate the type and amount of bacteria present in chronic wounds. Assessment of wound bio-burden using semi-quantitative swabs revealed a statistically significant reduction in the relative amount of bacteria following a single treatment of ultraviolet light (UVC).
The greatest reduction in semi-quantitative swab scores following ultraviolet light C treatment were observed for wounds colonized with the bacteria Pseudomonas aeruginosa and wounds colonized with only one species of bacteria. Significant (P <0.05) reductions in the relative amount of bacteria also were observed in 12 ulcers in which methicillin-resistant Staphylococcus aureus was present.
These results confirm previous laboratory studies and demonstrate that ultraviolet light C can kill bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus present in superficial layers of chronic wounds.
In situations where the bio-burden levels are more representative of the contamination in areas such as operating/emergency rooms (102 CFU/cm2 ), UV-C is capable of completely deactivating the entire population at lower doses, most likely less than 100 milliJoules/cm2 . Test surfaces contaminated with high numbers of spores that are subsequently spread across the surface area as may occur during precleaning were readily decontaminated or sterilized with adequate doses of UV-C.
Evidence shows even at low power, UV-C is capable of completely deactivating the entire population, most likely less than 100 milliJoules/cm2.
Again, contaminants subsequently spread across the surface area during precleaning, are then readily decontaminated or sterilized with adequate doses of UV-C.
Spores at contamination levels of 105 to 106 CFU/cm2 and applied in powder dense enough to be visible to the naked eye indicated a 1-log reduction after UV-C doses of 1,000 to 16,000 milliJoules/cm2. These findings emphasize the need for precleaning contaminated surfaces of gross material. Use of a precleaning step, such as HEPA-vacuuming or damp wiping, for heavily contaminated surfaces in the presence of visible soil, followed by UV-C exposure, should effectively decontaminate the area or surface. This is substantiated by the data in which total kill was demonstrated from surfaces contaminated with less-concentrated spore suspensions in the absence of visible powder.
Prior studies in animal laboratory settings using UV light showed a significant reduction of bacterial High-Dose Ultraviolet C Light Inactivates Spores.In this study where the organisms were spread on the test surface without deactivation or removal by any cleaning agent, a significant spore reduction was observed after UV-C irradiation.
A recent study by Nicholson and Galeano (2003) found “the data indicate that standard UV treatments that are effective against B. subtilis spores are likely also sufficient to inactivate B. anthracis spores, and spores of standard B. subtilis strains could reliably be used as a biodosimetry model for the UV inactivation of B. anthracis spores”.
Our investigations have confirmed this finding. From these experimental findings one may reasonably conclude that the UVAS device, or other UV-C generating devices, could decontaminate areas in which surface contamination was 102CFU/cm2 and could be used to decontaminate extremely concentrated surfaces as long as a precleaning step was instituted.
In simplistic terms, irradiance is a measure of how “bright” the UV source is as observed by the surface of the formulation during curing. Also stated simply, energy density is a combination of how “bright” the UV source is and how long the formulation is exposed. More specifically, irradiance is the instantaneous number of photons at a specific wavelength or range of wavelengths striking the surface per unit area, and is expressed in watts per square centimeter. Peak irradiance is the maximum irradiance that the surface experiences during the curing process. Energy density is the time-integral of irradiance and represents the total sum of photons of a specific wavelength or wavelength range received by a specific area of the surface within a specific length of time. Energy density is typically expressed in units of Joules per square centimeter.
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