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An ultraviolet (UV) marker is a pen whose marks are fluorescent but transparent: the marks can be seen only under an ultraviolet light. They are commonly used in security situations to identify belongings or to prevent the reproduction of unauthorized banknotes. UV pens can now be bought at some stationery shops to securely mark items of high value in case of theft.
The body of a UV marker is made by plastic similar to a normal marker.
The ink used in UV markers has been made from various things in the past such as lemon juice, vinegar, diluted blood or even urine.Modern UV-invisible ink is mainly made by a fluorescent derived from things in nature that glow when exposed to an ultraviolet light. The main components include dilute laundry detergent, body fluids, tonic water and vitamin B-12 dissolved in vinegar.
There are different types of UV-invisible ink: opaque, semi-opaque and translucent. All of the three contain acrylic monomers which contain a diluent and a photoinitiator to participate in the curing reaction and to respond to UV radiation. Photoinitiators is a very important element for making the ink as it is the substance that absorbs the UV mission of a UV light, which enable the marker to work.
The UV LEDs used to read the message written by UV markers emits near-ultraviolet light. This near-ultraviolet radiant energy is also called black light which fall just outside the visible spectrum with a wavelength of 380 nm. Such wavelength are very narrow and will fall within a much broader band than regular fluorescent black lights. Therefore, UV LEDs are completely safe. It will cause no damage to eyes nor risks of skin cancer. When the black light falls upon the UV-visible ink, it makes the ink fluoresce, where it emits visible light and make the message readable for human eyes.
Fluorescence is caused by a conversion of energy; when the invisible ultraviolet falls on the fluorescent surface, it is absorbed and re-emitted as visible light radiation. The absorption of energy by the electrons in the UV-visible ink enables this to happen. When an extra amount of energy is absorbed, the electrons jump into higher energy orbital patterns surrounding the nucleus. Eventually, the energy is released as visible light when they fall back to their normal orbital shell. [ citation needed ]The difference between the original electron orbital and the new orbital pattern will determine the color of the fluorescent.
In some cases, people can also use photocopiers to develop UV-visible ink message as the head of the photocopiers contain UV components.
Commercially available UV markers are used to mark things for security purpose, such as to check for counterfeit money and mark property in the event of theft for the purpose of identifying ownership. It is also sometimes used in identifying whether a similar documents is an original copy.
UV markers are also widely used on credit cards or lottery ticket for authentic purpose. For example, in the state of Illinois, the lottery tickets are stamped with UV-invisible ink to indicate authenticity whereas credit cards are marked with a particular logo or the card type. Moreover, various countries use UV markers to create marks on stated issued driving licenses and identity cards to ensure they are authentic.Other cases include retailers marking their items to avoid customers to exchange or return items they were not originally bought from their stores.
Many people and organizations use UV marker to protect and hide sensitive messages from the public. Especially during the war time, UV-invisible was widely used in militaries to hide secret messages and important addresses to avoid their enemy to have detail information on their next step of action as this will put them on advantage by providing them time to prepare and giving them chances to destruct their plans.
During World War II., a battle between laboratories to develop the best UV invisible ink was revealed between the Allies & the Axis powers. They were desperately trying to develop new, better UV-invisible inks that can only be revealed by a very few type of UV light with a very particular size of wavelength. This is not only because so that they can hide more messages from their enemy but this will also allow them to find out the method to read the hidden message of by their enemy.
People use UV markers to inspect whether the cleaner has cleaned the toilet properly and rank how well the toilet is cleaned. The marker used in this case is a lotion, which is non-toxic and water-soluble, so it can easily be removed by soap and water solutions. The UV marker is applied to the underside of the toilet seat. It is not readily visible under regular room lighting. The toilet will then be visually inspected with a hand-held UV light to rank how well the toilet is cleaned a few days later. The inspector will then make a visual score; 1 represents light fluorescence, 2 for moderate, 3 for heavy and 0 represented no fluorescence. This scoring system is based on visual inspection and an average cleaning score will be calculated. If no cleaning was taken place, the marker will show heavy fluorescence which will at least last for 7 days after it was applied. The less the marker is found, the better the toilet is being cleaned.
Messages written by a UV marker can be discovered by the incorrect people when there is a change of reflectivity of the paper or a pen scratches mark on the paper. The smell of the ink also reduces the security of secret messages as the hidden messages can be easily found with the help of trained animals.
UV marker should not be used on surfaces that may already contain similar elements found in the UV marker ink, such as the high brightness copier papers. This is because the message will not be shown clearly as the surface will change color or react along with the ink when under UV light. Therefore, we should always test on surface in an inconspicuous area to determine results. Similarly, when writing with a UV marker on very smooth and glossy surfaces, the ink will only show an unclear outline of what is written and may be rubbed off easily. This is because the ink is prevented from being deeply absorbed into the surface like it would on a piece of normal paper. Moreover, messages can be easily visible when exposed under glancing light.
Unlike other invisible inks, which require heat or placing chemical liquid over to reveal the message, the UV invisible ink can be screened and read quickly with an ultraviolet light source without damaging or changing the surface of the paper. This means that people will not be able to tell or notice if a secret message has been intercepted by a third party.
The electromagnetic spectrum is the range of frequencies of electromagnetic radiation and their respective wavelengths and photon energies.
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. The most striking example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, while the emitted light is in the visible region, which gives the fluorescent substance a distinct color that can be seen only when exposed to UV light. Fluorescent materials cease to glow nearly immediately when the radiation source stops, unlike phosphorescent materials, which continue to emit light for some time after.
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms, it can cause chemical reactions and causes many substances to glow or fluoresce. Consequently, the chemical and biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules.
Invisible ink, also known as security ink or sympathetic ink, is a substance used for writing, which is invisible either on application or soon thereafter, and can later be made visible by some means. Invisible ink is one form of steganography.
Ultraviolet–visible spectroscopy or ultraviolet–visible spectrophotometry refers to absorption spectroscopy or reflectance spectroscopy in part of the ultraviolet and the full, adjacent visible spectral regions. This means it uses light in the visible and adjacent ranges. The absorption or reflectance in the visible range directly affects the perceived color of the chemicals involved. In this region of the electromagnetic spectrum, atoms and molecules undergo electronic transitions. Absorption spectroscopy is complementary to fluorescence spectroscopy, in that fluorescence deals with transitions from the excited state to the ground state, while absorption measures transitions from the ground state to the excited state.
A cuvette is a small tube-like container with straight sides and a circular or square cross section. It is sealed at one end, and made of a clear, transparent material such as plastic, glass, or fused quartz. Cuvettes are designed to hold samples for spectroscopic measurement, where a beam of light is passed through the sample within the cuvette to measure the absorbance, transmittance, fluorescence intensity, fluorescence polarization, or fluorescence lifetime of the sample. This measurement is done with a spectrophotometer.
A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than incandescent lamps. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output.
A blacklight, also referred to as a UV-A light, Wood's lamp, or ultraviolet light, is a lamp that emits long-wave (UV-A) ultraviolet light and very little visible light.
Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet, visible light (400–750 nm) or infrared radiation (750–2500 nm).
A whiteboard is a glossy, usually white surface for making nonpermanent markings. Whiteboards are analogous to blackboards, but with a smoother surface allowing rapid marking and erasing of markings on their surface. The popularity of whiteboards increased rapidly in the mid-1990s and they have become a fixture in many offices, meeting rooms, school classrooms, and other work environments.
A marker pen, fineliner, marking pen, felt-tip pen, flowmarker, texta, sketch pen or koki, is a pen which has its own ink source and a tip made of porous, pressed fibers such as felt. A permanent marker consists of a container and a core of an absorbent material. This filling serves as a carrier for the ink. The upper part of the marker contains the nib that was made in earlier times of a hard felt material, and a cap to prevent the marker from drying out. Until the early 1990s, the most common solvents that were used for the ink were toluene and xylene. These two substances are both harmful and characterized by a very strong smell. Today, the ink is usually made on the basis of alcohols. Markers may be waterproof, dry-erase, wet-erase, or permanent.
A fluorophore is a fluorescent chemical compound that can re-emit light upon light excitation. Fluorophores typically contain several combined aromatic groups, or planar or cyclic molecules with several π bonds.
A germicidal lamp is an electric light that produces ultraviolet C (UVC) light. This short-wave ultraviolet light disrupts DNA base pairing, causing formation of pyrimidine dimers, and leads to the inactivation of bacteria, viruses, and protozoa. It can also be used to produce ozone for water disinfection.
A chromophore is the part of a molecule responsible for its color. The color that is seen by our eyes is the one not absorbed within a certain wavelength spectrum of visible light. The chromophore is a region in the molecule where the energy difference between two separate molecular orbitals falls within the range of the visible spectrum. Visible light that hits the chromophore can thus be absorbed by exciting an electron from its ground state into an excited state. In biological molecules that serve to capture or detect light energy, the chromophore is the moiety that causes a conformational change of the molecule when hit by light.
Luminous paint or luminescent paint is paint that exhibits luminescence. In other words, it gives off visible light through fluorescence, phosphorescence, or radioluminescence. There are three types of luminous paints.
UV tattoos or blacklight tattoos are tattoos made with dyes that fluoresce visibly under an ultraviolet light, not unlike fluorescein or rhodamine. Depending upon the ink chosen a UV tattoo can be nearly invisible when illuminated only by light within the visible spectrum. Therefore, they have found popularity with people seeking a subtler tattoo. UV tattoos are particularly popular in the raver community for their distinctive appearance. Although UV tattoos are sometimes considered invisible in normal light, scarring produced by the tattoo machine in the application process will remain, and therefore still show. Smaller tattoos will be easier to recognize as tattoos, while larger tattoos are more likely to be recognized as a scar at first glance. A UV tattoo becomes visible under blacklight, when it fluoresces in colors ranging from white to purple, depending upon the ink chosen.
A photopolymer or light-activated resin is a polymer that changes its properties when exposed to light, often in the ultraviolet or visible region of the electromagnetic spectrum. These changes are often manifested structurally, for example hardening of the material occurs as a result of cross-linking when exposed to light. An example is shown below depicting a mixture of monomers, oligomers, and photoinitiators that conform into a hardened polymeric material through a process called curing. A wide variety of technologically useful applications rely on photopolymers, for example some enamels and varnishes depend on photopolymer formulation for proper hardening upon exposure to light. In some instances, an enamel can cure in a fraction of a second when exposed to light, as opposed to thermally cured enamels which can require half an hour or longer. Curable materials are widely used for medical, printing, and photoresist technologies.
Ultraviolet photography is a photographic process of recording images by using light from the ultraviolet (UV) spectrum only. Images taken with ultraviolet light serve a number of scientific, medical or artistic purposes. Images may reveal deterioration of art works or structures not apparent under visible light. Diagnostic medical images may be used to detect certain skin disorders or as evidence of injury. Some animals, particularly insects, use ultraviolet wavelengths for vision; ultraviolet photography can help investigate the markings of plants that attract insects, while invisible to the unaided human eye. Ultraviolet photography of archaeological sites may reveal artifacts or traffic patterns not otherwise visible.
A photocatalyst activity indicator ink (Paii) is a substance used to identify the presence of an underlying heterogeneous photocatalyst and to measure its activity. Such inks render visible the activity of photocatalytic coatings applied to various "self-cleaning" products. The inks contain a dyestuff that reacts to ultraviolet radiation in the presence of the photocatalytic agent in the coating. They are applied to the coated product using a pen or brush, and show a color change or disappearance when exposed to ultraviolet.
Tagging of postage stamps means that the stamps are printed on luminescent paper or with luminescent ink to facilitate automated mail processing. Both fluorescence and phosphorescence are used. The same stamp may have been printed with and without these luminescent features, the two varieties are referred to as tagged and untagged, respectively.