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New materials

Small solutions

In the state of Pernambuco, nanotechnology and photonics are the basis of sensors in the environmental and health care areas

One of the first products developed in Brazil using nanometric technology is ready to leave the laboratory and incorporate itself  into day-to-day living. It is a molecule that has the function of dosing the intensity of solar rays in accordance with the sensitivity of human skin. It is installed in a badge, for example, and helps workers who have the sun as a companion, such as traffic guards, to not overexpose themselves to solar radiation. This is a problem to be avoided because excess can result in skin cancer, a disease caused by ultraviolet rays (UV), which arrive on the earth together with sunlight, and bring about more than 100,000 cases per year in the country, according to the National Cancer Institute.

Called n-Domp (molecular nanodosimeter for personal use), the molecule is one of the many projects in the area of nanotechnology led by Petrus D’Amorim Santa-Cruz, the coordinator at the Photonic Nano-Devices Laboratory of the Federal University of Pernambuco (UFPE). For the development and final format of n-Domp and of other future products, professor Santa-Cruz and seven other students responsible for the research, founded the company Ponto Quântico, which is installed in the UFPE incubator. Both the laboratory and the company make up part of the Molecular Nanotechnology and Interfaces Network (Renami), one of the nanotechnology networks of the Ministry of Science and Technology (MCT).

Evaluating risks
The nanodosimeter installed in a nametag is the company’s first nano-device. It was on show at the Brasiltec 2004, the exhibition on technological innovations that took place in November in Sao Paulo at the company’s stand. The target public for n-Domp are companies that contract traffic wardens, civil construction workers, and oil rig workers, and even for employees of the polymer industry that use artificial UV in the preparation of packaging surfaces and other products. “It serves to evaluate the risks of the users, says  Santa-Cruz. The working device is installed in a plastic nametag in the form of a film that measures between 40 and 50 nanometers of thickness (1 nanometer corresponds to 1 millimeter divided by 1 million). The molecule is “nano-mounted”  in three parts.

The first mimics the human skin and is degraded by the action of the UV rays, guarding the information on the dosage. The second, which includes the chemical element europium in the form of a cation (an atom that has lost one or more electrons), permits the reading of the dosage through the emission of light, and the final part blocks any interaction with water molecules that could interfere in the device’s working. “The molecule itself is the device”, says professor Santa-Cruz. The badge serves as a support, which facilitates the later reading of the dosage, with the help of a reader linked to a computer, which stores in a data bank the quantity of  UV light to which each person was exposed.

Santa-Cruz and his students already possess five prototypes in the area of nanotechnology with patents registered at the National Institute of Intellectual Property (Inpi). One of them is a further development for n-Domp. It deals with a sensor produced with Oled, namely Organic Light Emitting Diodes. Contrary to conventional LEDs, produced from inorganic semiconductors, such as silicon and gallium, these are manufactured with molecules with electrical properties that generate their own light when an electrical current passes. Known as n-Domoled, the device is produced as a sandwich of nanofilms. The active part of this product if made up of the same molecule projected for the previously mentioned device, which degrades with UV radiation. As the sensor emits light when it receives an electrical pulse, the accumulation of ultraviolet diminishes little by little the intensity of the luminous effect of the device. “This is the next generation of dosage meters that we are developing”, says Santa-Cruz.

Another of the research group’s patents serves in healthcare. It is a contribution for the production of a vitroceramics a material that has its origin in glass within a process of controlled crystallization under high temperature and which makes it highly resistant. The product can be used in bone prostheses and teeth, for example. “What we did was to induce the formation of a nanostructure of silver in this material, which possesses bactericidal and anti-inflammatory properties, in order to diminish the possibility of infections in the location of the implant.”  Silver has been known for millenniums for its bactericidal properties and was only totally abandoned for this end after the appearance of antibiotics. In the process of the production of the nano-structured material, silver cations gain electrons and then form metallic nano-spheres that migrate to the surface of the implant. In the biological median, the liberation of silver, in ionic form (with the loss or gain of an electron), occurs in a slow and gradual manner.

Rare light
The use of nano-structured materials has also resulted in a device for the mapping of temperature in biological environments such as the interior of the human body or in water. Making use of a nano-powder based on thulium and terbium, two Rare Earth Metals (from the Lanthanide Group of the Periodic Table), the researchers managed to map the temperature by a photonic means, with nanometric precision. As well as in the form of nano-powder, the same material was developed in bio-compatible optical fibers for the control of temperature along the fiber. The system can also be used in locations that cannot receive normal thermometers, such as in transformers and in areas with high magnetic fields. The intensity of the light emitted by this device is collected by a portable sensor that measures the relative intensity of the blue light produced by thulium in relation to the green light of terbium. The relationship between the light intensity of these two elements is what results in a temperature measurement. This relationship of intensities varies linearly with temperature in the range from -210°C up to 720°C.

In the environmental area the researchers from the Fundamental Chemistry Department of UFPE have developed an innovative sensor for measuring metallic pollutants in water. This is a product that is now in the automation phase at Ponto Quântico. Called SPA-Photon, the sensor is composed of a super absorbing polymer, of the same family of polymers used in baby nappies, doped with a photonic probe. Placed in the water that is to be analyzed, the polymer absorbs the liquid in up to two hundred times its own weight and concentrates the pollutant. The analysis, which can be done at the location with the measurement of a palmtop, is done by measuring the luminous radiation of the probe using a piece of software. The result appears according to how the light spectrum is modified by the type of metal. “We don’t measure the spectrum of the pollutant, but the spectrum of the light from the probe.”  Besides, the increase in concentration of the metal in the polymer is what makes the sample-sensor detect very small quantities of pollutant. “We know that this sensor is economically viable, but we have to automate it, for this reason we are developing more advanced software that will make the interpretation automatic.”

Residual pollutant
The Petrus team showed during Brasiltec 2004 that it is capable of formulating new materials that diverge from the principal target of their work in photonics and nanotechnology. In a doctoral thesis for the Science Material Program of UFPE, a residual pollutant coming from the milling of a type of porcelain, named after a special type of milled ceramic, was used for the development of composites to turn the gesso more compact and resistant. The experiment resulted in vitroceramics and glass which is in the testing phase for recovering the ceramic. All with the advantage of removing the residual pollutant from the environment, adding value to this by-product.  With all of this projected work and others that are in a state of formation, professor Santa-Cruz has a firm objective at the university. “Our idea is not just to graduate students, but also to develop the spirit of entrepreneurship in the areas of nanotechnology”, he says. He is doing this with the same disposition that he gives his lectures on nanotechnology in the post graduation course in the mornings, and twice per week in the evenings for Pernambuco State’s public school teachers doing their licentiate.