Atmospheric Pressure Plasma Jet as an Accelerator of Tooth Bleaching

Svrha: Željela se ispitati učinkovitost atmosferskoga plazmenog mlaza (APM) kao izvora svjetlosti čiji učinak može brže razlagati vodikov peroksid u gelovima za izbjeljivanje i tako potaknuti brže i bolje izbjeljivanje. Materijali i metode: U zeleni čaj je osam sati bilo uronjeno 25 pastila hidroksilapatita. Nakon toga su osušene i podijeljene u pet skupina s po pet pastila. Uzorci su posebno tretirani gelovima za izbjeljivanje s 30-postotnim i 40-postotnim vodikovim peroksidom te u kombinaciji s atmosferskom plazmom. Tijekom procesa izbjeljivanja analizirana je optička emisijska spektroskopija i temperatura s pomoću pirometra. Boja pastila bila je određena RGB kolorimetrom. Za mjerenje pH vrijednosti korišteno je prije i poslije tretmana dodatnih 10 pastila kojima je pH izmjeren kontaktnim pH-metrom. Rezultati: Analizom promjene boja na pastilama prije i poslije tretmana, pokazano je da APM u kombinaciji s gelovima za izbjeljivanje poboljšava izbjeljivanje 32, odnosno 15 posto. Postupak izbjeljivanja s pomoću APM-a imao je bolji učinak u šest puta kraćem vremenu u odnosu prema tretmanu koji je predložio proizvođač. Optičkom emisijskom spektroskopijom dokazana je kemijska aktivnost plazme. Nakon tretmana APM-om, pH vrijednosti gela za izbjeljivanje pale su na 50 do 75 posto početnih vrijednosti, a temperatura na površini tretiranog uzorka porasla je s 8 na 10˚C u odnosu prema početnim vrijednostima. Zaključak: Uporaba atmosferskoga plazmenog mlaza u kombinaciji s gelovima za izbjeljivanje daje bolje rezultate u kraćem vremenu i ne povećava temperaturu koja može oštetiti okolno tkivo.Objective: To study the effect of atmospheric pressure plasma (APP) jet as a potential accelerator of the degradation of hydrogen peroxide in bleaching gels which could lead to better and faster bleaching. Material and Methods: 25 pastilles of hydroxylapatite were colored in green tea for 8 hours and were randomly divided into five groups (n = 5). The bleaching process was performed with 30% and 40% hydrogen peroxide (HP) gel alone and in conjunction with helium APP jet. During the bleaching treatment, optical emission spectroscopy and non-contact surface temperature measurement using pyrometer were performed. Color of the pastilles was determined by a red– green–blue (RGB) colorimeter. PH values of bleaching gels were measured before and after the plasma treatment on additional 10 pastilles using a pH meter with contact pH electrode. Results: The color measurements of pastilles before and after the treatment showed that treatment with APP jet improved the bleaching effect by 32% and 15% in the case of 30 % and 40% HP gel. Better results were obtained approximately six times faster than with a procedure suggested by the bleaching gel manufacturer. Optical emission spectroscopy proved that plasma has a chemically active role on the gel. After the APP treatment, pH values of bleaching gels dropped to about 50–75% of their initial value while the surface temperature increased by 8–10˚C above baseline. Conclusion: The use of plasma jet provides more effective bleaching results in a shorter period of time without a significant temperature increase which may cause damage of the surrounding tissue

A Fiber Optic Catalytic Sensor for Neutral Atom Measurements in Oxygen Plasma

The presented sensor for neutral oxygen atom measurement in oxygen plasma is a catalytic probe which uses fiber optics and infrared detection system to measure the gray body radiation of the catalyst. The density of neutral atoms can be determined from the temperature curve of the probe, because the catalyst is heated predominantly by the dissipation of energy caused by the heterogeneous surface recombination of neutral atoms. The advantages of this sensor are that it is simple, reliable, easy to use, noninvasive, quantitative and can be used in plasma discharge regions. By using different catalyst materials the sensor can also be applied for detection of neutral atoms in other plasmas. Sensor design, operation, example measurements and new measurement procedure for systematic characterization are presented

Recent progress in cellulose hydrophobization by gaseous plasma treatments

Cellulose is an abundant natural polymer and is thus promising for enforcing biobased plastics. A broader application of cellulose fibers as a filler in polymer composites is limited because of their hydrophilicity and hygroscopicity. The recent scientific literature on plasma methods for the hydrophobization of cellulose materials is reviewed and critically evaluated. All authors focused on the application of plasmas sustained in fluorine or silicon-containing gases, particularly tetrafluoromethane, and hexamethyldisiloxane. The cellulose materials should be pre-treated with another plasma (typically oxygen) for better adhesion of the silicon-containing hydrophobic coating. In contrast, deposition of fluorine-containing coatings does not require pre-treatment, which is explained by mild etching of the cellulose upon treatment with F atoms and ions. The discrepancy between the results reported by different authors is explained by details in the gas phase and surface kinetics, including the heating of samples due to exothermic surface reactions, desorption of water vapor, competition between etching and deposition, the influence of plasma radiation, and formation of dusty plasma. Scientific and technological challenges are highlighted, and the directions for further research are provided.Slovenian Research and Innovation Agenc

Effect of VUV Radiation on Surface Modification of Polystyrene Exposed to Atmospheric Pressure Plasma Jet

Precise tailoring of surface properties by gaseous plasma treatments remains a key scientific challenge, especially when adequate surface wettability should be laterally distributed, and sharp interfaces between hydrophobic and hydrophilic areas are desirable. The evolution of surface wettability and functional groups on polystyrene (PS) upon treatment with argon plasma jet was monitored by water contact angles and X-ray photoelectron spectroscopy (XPS). An array of water droplets was deposited on PS samples treated either directly by the plasma jet or only VUV radiation arising from the plasma. Rather sharp interfaces between the activated and not-affected regions were observed in both cases. The functionalization with highly-oxidized carbon functional groups, as determined by high-resolution C1s XPS spectra, was by far more efficient using the VUV radiation only. In contrast, the optimal wettability was achieved using direct plasma treatment. The results were explained by different mechanisms involved in the interaction of radiation and reactive plasma species with the polymer surface

Advanced method for efficient functionalization of polymers by intermediate free-radical formation with vacuum-ultraviolet radiation and producing superhydrophilic surfaces

An efficient approach for tailoring surface properties of polymers is presented, which enables rapid modification leading to superhydrophilic properties. The approach is based on vacuum-ultraviolet radiation (VUV) pretreatment of the surface to create reactive dangling bonds. This step is followed by a second treatment using neutral oxygen atoms that react with the dangling bonds and form functional groups. The beneficial effect of VUV pretreatment for enhanced functionalization was clearly demonstrated by comparing VUV pretreatment in plasmas created in different gases, i.e., hydrogen, nitrogen, and oxygen, which differ in the intensity of VUV/UV radiation. The emission intensity of VUV radiation for all gases was measured by vacuum ultraviolet spectroscopy. It was shown that VUV has a strong influence on the treatment time and final surface wettability. A superhydrophilic surface was obtained only if using VUV pretreatment. Furthermore, the treatment time was significantly reduced to only a second of treatment. These findings show that such an approach may be used to enhance the surface reaction efficiency for further grafting of chemical groups

Modifikacija površine PET-polimera z dušikovo plazmo

Low pressure weakly nitrogen plasma was applied for incorporation of nitrogen-containing functional groups onto poly(ethylene terephthalate) - PET polymer. Nitrogen plasma was created in an electrode-less radiofrequency discharge at the nominal power of 200 W and the frequency of 27.12 MHz. Nitrogen molecules entered the discharge region were highly excited, partially dissociated and weakly ionized. Transformation into the state of plasma allowed for creation of chemically reactive particles with a high potential energy while the kinetic energy remained close to the value typical for room temperature. The chemical reactivity allowed for rapid functionalization with nitrogen-rich functional groups. The appearance of these groups was monitored by X-ray photoelectron spectroscopy - XPS. The polymer surface was quickly saturated with nitrogen indicating that the modification was limited to an extremely thin surface film.Nizkotlačno, šibko ionizirano dušikovo plazmo smo uporabili za površinsko modifikacijo polimera polietilen tereftalat z dušikovimi funkcionalnimi skupinami. Plazmo smo vzbujali v brezelektrodni visokofrekvenčni plinski razelektritvi z generatorjem, ki deluje pri koristni moči okoli 200 W in osnovni frekvenci 27,12 MHz. Dušikove molekule, ki vstopijo v plinsko razelektritev, se vzbudijo v visoka vzbujena stanj, delno disociirajo in šibko ionizirajo. Transformacija plina v stanje plazme omogoča nastanek kemično reaktivnih delcev z veliko potencialno energijo, medtem ko ostane njihova kinetična energija blizu vrednosti, ki je značilna za plinske molekule pri sobni temperaturi. Velika kemijska reaktivnost dušikove plazme omogoča hitro funkcionalizacijo površine PET-polimera z dušikom bogatimi funkcionalnimi skupinami. Ta pojav smo spremljali z rentgensko fotoelektronsko spektroskopijo. Polimerni vzorci so postali hitro nasičeni z dušikom, iz česar je mogoče sklepati, da je funkcionalizacija omejena na zelo tanko plast prav ob površini vzorcev

Kinetics of Surface Wettability of Aromatic Polymers (PET, PS, PEEK, and PPS) upon Treatment with Neutral Oxygen Atoms from Non-Equilibrium Oxygen Plasma

The wettability of polymers is usually inadequate to ensure the appropriate spreading of polar liquids and thus enable the required adhesion of coatings. A standard ecologically benign method for increasing the polymer wettability is a brief treatment with a non-equilibrium plasma rich in reactive oxygen species and predominantly neutral oxygen atoms in the ground electronic state. The evolution of the surface wettability of selected aromatic polymers was investigated by water droplet contact angles deposited immediately after exposing polymer samples to fluxes of oxygen atoms between 3 × 1020 and 1 × 1023 m−2s−1. The treatment time varied between 0.01 and 1000 s. The wettability evolution versus the O-atom fluence for all aromatic polymers followed similar behavior regardless of the flux of O atoms or the type of polymer. In the range of fluences between approximately 5 × 1020 and 5 × 1023 m−2, the water contact angle decreased exponentially with increasing fluence and dropped to 1/e of the initial value after receiving the fluence close to 5 × 1022 m−2

Comparison of SF6 and CF4 Plasma Treatment for Surface Hydrophobization of PET Polymer

The fluorination of the polymer polyethylene terephthalate in plasma created from SF6 or CF4 gas at various pressures was investigated. The surface was analysed by X-ray photoelectron spectroscopy and water contact angle measurements, whereas the plasma was characterized by optical emission spectroscopy. The extent of the polymer surface fluorination was dependent on the pressure. Up to a threshold pressure, the amount of fluorine on the polymer surface and the surface hydrophobicity were similar, which was explained by the full dissociation of the SF6 and CF4 gases, leading to high concentrations of fluorine radicals in the plasma and thus causing the saturation of the polymer surface with fluorine functional groups. Above the threshold pressure, the amount of fluorine on the polymer surface significantly decreased, whereas the oxygen concentration increased, leading to the formation of the hydrophilic surface. This effect, which was more pronounced for the SF6 plasma, was explained by the electronegativity of both gases

Mechanisms Involved in the Modification of Textiles by Non-Equilibrium Plasma Treatment

Plasma methods are often employed for the desired wettability and soaking properties of polymeric textiles, but the exact mechanisms involved in plasma–textile interactions are yet to be discovered. This review presents the fundamentals of plasma penetration into textiles and illustrates mechanisms that lead to the appropriate surface finish of fibers inside the textile. The crucial relations are provided, and the different concepts of low-pressure and atmospheric-pressure discharges useful for the modification of textile’s properties are explained. The atmospheric-pressure plasma sustained in the form of numerous stochastical streamers will penetrate textiles of reasonable porosity, so the reactive species useful for the functionalization of fibers deep inside the textile will be created inside the textile. Low-pressure plasmas sustained at reasonable discharge power will not penetrate into the textile, so the depth of the modified textile is limited by the diffusion of reactive species. Since the charged particles neutralize on the textile surface, the neutral species will functionalize the fibers deep inside the textile when low-pressure plasma is chosen for the treatment of textiles

A review of recombination coefficients of neutral oxygen atoms for various materials

Relevant data on heterogeneous surface recombination of neutral oxygen atoms available in the scientific literature are reviewed and discussed for various materials. The coefficients are determined by placing the samples either in non-equilibrium oxygen plasma or its afterglow. The experimental methods used to determine the coefficients are examined and categorized into calorimetry, actinometry, NO titration, laser-induced fluorescence, and various other methods and their combinations. Some numerical models for recombination coefficient determination are also examined. Correlations are drawn between the experimental parameters and the reported coefficients. Different materials are examined and categorized according to reported recombination coefficients into catalytic, semi-catalytic, and inert materials. Measurements from the literature of the recombination coefficients for some materials are compiled and compared, along with the possible system pressure and material surface temperature dependence of the materials’ recombination coefficient. A large scattering of results reported by different authors is discussed, and possible explanations are provided