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Pectinases are a type of enzymes frequently used in the food industry to clarify, liquefy, and stabilize fruit juices. The main challenge in fruit juice production is the cloudiness of the juice, which is largely caused by the presence of pectic polysaccharides. Endo-pectinases are enzymes that hydrolyze the glycosidic bonds in pectic polymers. Commercial pectinolytic enzymes are typically produced by fungi, with Aspergillus spp. being the most commonly used. The aim of this research was the production and characterization of a novel endo-pectinase from the Aspergillus tubingensis strain for use in liquefying and clarifying different types of fruit juice. To accomplish this, solid-state fermentation was conducted on agricultural waste, such as sugar beet pulp and wheat bran, to produce pectinolytic enzymes. The resulting crude extract was concentrated via ultrafiltration and used to isolate the endo-pectinase via ammonium sulfate and ethanol precipitation methods. Ion-exchange chromatography technique on DEAE Sephadex A-25 matrix was used for further purification of the endo-pectinase. The purified enzyme was characterized by the determination of total pectinolytic activity, specific pectinolytic activity, and SDS-PAA gel electrophoresis. The activity of the endo-pectinase was confirmed by a diffusion test and zymography with Ruthenium Red visualization. The resulting enzyme was used to liquefy apricot, banana, apple, quince, strawberry, and orange pulp, with juice yields ranging from 71% to 83%, depending on the fruit used. The juices treated with endo-pectinase showed much higher clarification compared to untreated juices. Additionally, the treated juices demonstrated more pronounced antioxidant properties, as determined through the DPPH assay.

In this work, signal enhancement of the original TEA CO2 LIBS setup was studied. Two different methods for copper nanoparticle synthesis were applied. Obtained nanoparticles were characterized and then used for Nanoparticle-Enhanced Laser-Induced Breakdown Spectroscopy (NELIBS) of plastic polypropylene. Preliminary results have shown that improvement in the analytical sensitivity for the detection of Cr in plastic materials was achieved.

In this work, Ag-doped ZnO nanoparticles are synthesized by using two-step laser synthesis. First, pulsed laser deposition (PLD) is used for deposition of Ag films on ZnO substrate. Such synthesized ZnO substrate covered with Ag layer is than put in the water in order to produce colloidal solution of Ag-doped ZnO nanoparticles by pulsed laser ablation in liquid (PLAL). Nd:Yag laser (pulse repetition 5 Hz, pulse duration 5 ns pulse duration, wavelength 1064 nm, single laser shot energy 300 mJ) was used for irradiation of targets in PLD and PLAL process [1]. In order to vary the Ag ratio in ZnO nanoparticles with different Ag ratio, different number of pulses (50, 200, 500, 1000, 2000 and 3000) were used in PLD for Ag deposition. The ratio of Ag dopant in ZnO nanoparticles strongly depends on the thickness of Ag layer at ZnO target. In each of six synthesized colloidal solutions Ag weight ratio is calculated using the data obtained by two various techniques, ICP-OES and XPS, while their photocatalytic performance is tested for degradation of Methylene Blue under UV irradiation. Various experimental techniques (XRD, XPS, SEM, UV-Vis) were used to determine the crystall structure, size- distribution and optical properties of Ag-doped ZnO nanoparticles. In this work we discuss the dependence of MB photodegradation rate on Ag-dopant ratio calculated from both methods, ICP-OES and XPS. Ag- doping is shown to increase the MB photodegradation rate about two times twice at 0.32 wt% of Ag in ZnO (calculated from ICP-OES). [1] Blažeka, D. ; Car, J. ; Klobučar, N. ; Jurov, A. ; Zavašnik, J. ; Jagodar, A. ; Kovačević, E. ; Krstulović, N. Photodegradation of Methylene Blue and Rhodamine b Using Laser-Synthesized ZnO Nanoparticles. Materials (Basel). 2020, 13, 1–15, doi:10.3390/ma13194357.

Hard-tissue replacements are most commonly made from the Ti-based materials, such as commercially pure titanium (CP-Ti) and Ti-6Al-4V (mass%) alloy, because of their exceptional biocompatible properties combined with the excellent corrosive and mechanical characteristics [1]. More recently, efforts have been made to additionally enhance the properties of the metallic implants through the careful selection of the alloy composition and surface modification technics [2,3]. As a result, second-generation β-type Ti alloys, containing non-toxic elements, have been developed. One of the promising β-type implant alloys is Ti-13Nb-13Zr (mass%). Even though the corrosion resistance and mechanical properties of this alloy are improved in comparison to the commonly used metallic implant materials, its biocompatible and osseointegration properties can and must be additionally enhanced. For that purpose several surface modification technics can be used, however, laser irradiation stands out as the most promising one. Because of that scope of the present research was to investigate the possibility of successful surface modification of the most commonly used implant material, i.e. CP-Ti, and the second-generation Ti-13Nb-13Zr alloy by utilizing the easy-to-apply laser irradiation method in order to obtain improved implant tribocorrosive properties and enhanced biointegration and bioactivity. Laser surface modifications were conducted using the Nd:YAG system in the air and argon atmosphere under different laser output energies. Implant materials surface morphologies after the laser irradiation treatment were investigated using the field-emission scanning electron microscopy (FE-SEM) and optical profilometry, while the impact of the laser irradiation on the implant materials surface characteristics were examined using the energy dispersive spectrometry (EDS) and microhardness measurements. Conducted research showed that utilization of the Nd:YAG laser irradiation resulted in significant alterations of the CP-Ti and Ti-13Nb-13Zr alloy surface chemistry, morphology and microhardness. Laser irradiation of both investigated materials led to the formation of visible microcracks and hydrodynamic effects in the central part of the irradiated area, while traces of melted and solidified material were observed at its periphery. More pronounced morphological changes were induced during the laser irradiation in an argon atmosphere, while a higher degree of texturing was recorded at the surface of the Ti-13Nb-13Zr alloy. At the irradiated surfaces, the formation of the oxide layer, predominantly composed of Ti-oxide particles, was detected. Surface oxides are desirable since their presence can improve the implant material bioactivity with a simultaneous increase of the tribo-corrosive properties through the formation of the hard corrosion resistance surface film. Laserinduced chemical and morphological alterations were more distinctive in the case of the Ti-13Nb- 13Zr alloy.

Titanium alloys are finding increasing use as biomaterials due to their low elastic modulus and high damage tolerance. However, the somewhat inadequate alloy surface performance can impede their biomedical application. Surface modification methods have been therefore developed to improve the alloys' surface bioactivity and osseointegration. Laser treatment allows the alloy surface to be modified, providing it with new functionalized surface chemistry and morphology, without compromising the rest of the material properties. Thus, the aim of the study was to examine the laser-induced alterations generated on the Ti-45Nb alloy surface by an ultrashort pulsed laser. The obtained results reveal that laser beam interaction with the target material led to the formation of significant alterations in surface morphology. Surface craters, microcracks, and surface features in the form of periodic and rippled structures and solidified droplets can be observed in the irradiated area. Also, it was found that the higher damage degree along with the material depth and the higher surface roughness were achieved during the irradiation in the argon atmosphere due to the formation of the more pronounced morphological changes on the alloy surface that are induced by higher laser ablation. Furthermore, obtained results showed that alloy surface modification in air, argon, and nitrogen atmosphere additionally caused changes in the surface chemical composition. Namely, after irradiation, the presence of oxygen was observed in the central irradiated area indicating the formation of bioactive Ti-oxide surface film with content that varies with the irradiation parameters variation. Therefore, laser beam irradiation can be singled out as the surface modification method for efficient inducement of the specific surface characteristics that can provide titanium alloys with enhanced osseointegration properties.

We report preliminary results of an innovative approach based on nanomaterials deposition on the sample surface for the improvement of the limit of the detection of LaserInduced Breakdown Spectroscopy (LIBS) analysis of trace elements in aluminum alloys. For this purpose, Ag-TiO2 bimetallic nanoparticles were synthesized and used to enhance the emission signal of laser-induced plasma.

Laser-Induced Breakdown Spectroscopy (LIBS) has become a very popular analytical method given some of its unique features such as applicability to any type of sample, practically no sample preparation, stand-off sensing capability, speed of analysis, and a possibility to analysis even the light elements. In this paper, we present a unique laboratory LIBS setup developed in our research group. This system uses infrared TEA CO 2 laser as the excitation source and time-integrated spatially resolved (TISR) signal detection. In our recent publications, we have demonstrated the potential of using the cost- effective TEA CO 2 based LIBS system not only for the fast elemental analysis but also for the simultaneous determination of hardness of materials.

This paper gives an overview of analytical capabilities of the laser induced breakdown spectroscopy (LIBS) system, based on Transversely-Excited Atmospheric pressure (TEA) CO2laser, and time-integrated, spatially-resolved detection, for the analysis of solid materials. The developed LIBS system is unique, and differs from the commonly used systems in two respects. The first one is the laser used as an energy source for plasma generation, and the second one is the applied non-gated detection scheme. Various types of materials were analyzed, from metals to biological samples, under different experimental conditions. The obtained results were critically evaluated and compared to the results obtained using commercially available LIBS that comprises Nd:YAG laser and time-gated detection.It was concluded that when it comes to detectability, precision and sensitivity, this simple and cost effective LIBS system may be regarded highly competitive to standard LIBS systems. Physical chemistry 2016 : 13th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-30 September 2016.

Physical chemistry / hysical chemistry - spectroscopy and Physical chemistry - material science Област проучавања ове дисертације је интеракција ласерског зрачења са металима. Ова актуелна научна област, значајна је како због бољег разумевања сложених процеса до којих долази приликом ове интеракције, тако и због бројних могућих примена. Предмет проучавања ове дисертације је интеракција зрачења импулсног наносекундног угљендиоксидног ласера са бакарном метом. Бакар је изабран као мета због великог значаја коју овај метал и његове легуре имају у савременим технологијама. Поред тога, у литератури нема података о индуковању плазме на бакру под дејством зрачења чији су интензитети реда величине од 30 до 110 MW cm-2, што је представљало својеврстан научни изазов. Циљ ове дисертације је, пре свега, проналажење оптималних експерименталних услова за стварање ласерски индуковане плазме под дејством зрачења импулсног TEA CO2 ласера на бакарну мету. Испитан је утицај стања површине мете, начина фокусирања ласерског зрачења, састава (азот, аргон, хелијум и ваздух) као и притиска (од 0,1 mbar до 1013 mbar) околног гаса на услове за стварање плазме. Спектрална емисија ласерски индуковане плазме проучавана је методом временски-интеграљене просторно-разложене оптичке емисионе спектроскопије. Посебна пажња посвећена је спектрoскопији плазме индукованој у атмосфери ваздуха. Показало се да се оптимални услови за стварање плазме постижу повећањем храпавости површине мете, постављањем мете +1,5 cm изван фокуса и снижавањем притиска ваздуха на 0,1 mbar. Резултати добијени у овој тези показали су да се посматрањем емисије из одређених зона плазме (на одређеним растојањима од површине мете) може постићи добар однос линије према позадини и линије према шуму и без временског разлагања сигнала. Ово је значајно са становишта поједностављења експерименталне технике.Такође, резултати показују да плазма индукована при коришћеним експеримeнталним условима има повољне карактеристике за спектрохемијску примену, јер се емисиони спектар састоји од добро разложених, оштрих и интензивних линија и континуалног зрачења врло ниског интензитета. Овакав закључак потврђују и границе детекције које су одређене за елементе присутне у траговима у узорцима бакра и месинга, а које су биле у опсегу 10 ppm. У овој тези проучаване су и морфолошке промена на бакарној мети које настају под дејством зрачења TEA CO2 ласера. Један мањи део истраживања урађен је коришћењем фемтосекундног титан-сафирног ласера, при чему је интензитет ласерског зрачења био у опсегу од 1012 до 1015 MW cm-2. За карактеризацију површине узорка пре и након озрачивања коришћене су различите технике: оптичка и електронска микроскопија, као и профилометрија. Дејство наносекундног ласера огледа се у формирању релативно глатких региона који су условљени топљењем бакра као и у хемијским променама на површини мете. Са порастом броја акумулираних импулса укупан ефекат добијен озрачивањем наносекундним ласерским зрачењем је “чишћење” мете, које може бити од значаја за примену у електроници. Дејство фемтосекундног ласера карактерише појава периодичних површинских структура што може имати значајну примену у оптици и електроници, нарочито у фотолитографији. This thesis is devoted to studies of the interaction of intense laser pulses with metal targets. This advanced area of research is essential for better understanding of the complex processes that occur during interaction of laser radiation with metal surfaces, and also because of a number of useful applications. The subject of research of this thesis is the interaction of a nanosecond carbon dioxide laser pulses with a copper target. The copper was selected as a target material because of a great importance of this metal and his alloys in advanced technologies. In addition, in the literature there is a lack of data concerning creation of copper plasma by using the laser pulses of low/moderate intensity. Thus, generation of copper plasma using laser peak intensities in the range of 30 to 110 MW cm-2 was a motivating task. The main aim of these investigations was to find optimal experimental conditions for the generation of plasma during irradiation of a copper target with TEA CO2 laser pulses. The influence of target surface state, focusing conditions, composition (nitrogen, argon, helium, air) and pressure (0.1 to 1013 mbar) of the surrounding atmosphere was studied. The spectral emission of laser induced plasma was studied using time-integrated spatially-resolved optical emission spectroscopy. A special attention was paid to a laser induced plasma spectroscopy studies under the ambient air. It was found that the optimal conditions for target plasma generation were obtained when targets with increased surface roughness were used, when the target was placed +1.5 cm out of the focus position, and when the air pressure was reduced to 0.1 mbar. The results have shown that good signal to noise and signal to background ratios could be obtained from emission measurements from spatially selected plasma zones, even without the use of time-gated detection. In the light of complexity of experimental setup, this result is of great importance. The emission spectra consisted of well resolved, sharp, and intense spectral lines, with very low background emission intensity. Thus, under the applied experimental conditions, the laser induced plasma has favorable characteristics for spectrochemical applications. Such conclusion was supported by the estimated limits of detection for trace elements detected in a copper and brass samples, which were in the range of 10 ppm. Morphological changes of a copper target induced by irradiation with TEA CO2 laser pulses were also studied. For these studies titanium-sapphire laser with the intensity of the laser radiation in the range 1012 to 1015 MW cm-2 was also used. For characterization of the target surface before and after the irradiation with laser light, different experimental techniques were used: optical microscopy, electron microscopy, and profilometry. The effect of nanosecond laser irradiation was the creation of relatively smooth areas caused by target melting, and also by the chemical changes of the surface. The cumulative effect of the increased number of accumulated laser pulses was some kind of surface cleaning which may find applications in electronics. The effect of femtosecond laser irradiation was appearance of periodic surface structures, which may find application in optics and electronics, especially in photolithography

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III International School and Conference on Photonics : PHOTONICA2011 : book of abstracts; August 29- September 2, 2011; Belgrade

Investigation was carried out on austenitic material samples – stainless steel and iron base superalloy that are widely used at elevated temperatures and pressures. The samples were exposed to Nd:YAG pulsed laser, with wavelength of 1064 nm and pulse duration of 170 ps. Different pulse energy and number of pulses were applied. Spots obtained by laser interaction were observed by optical and scanning electron microscope and analyzed by energo-dispersive spectroscopy. Vickers microhardness tests were performed. In this paper, the microstructural changes, arisen by different pulse energy and number of pulses, were discussed with the aim to determine optimal laser parameters in surface treatment process.

Interakcija lasera sa metalima proučava se decenijama, a posebno je intenzivirana u poslednje vreme, usled razvoja novih, efikasnih impulsnih lasera. Istraživanja u ovoj tezi su fokusirana na titanijum, koji poseduje niz odličnih osobina, što ga čini primenljivim u različitim savremenim tehnologijama. Obrada i procesiranje titanijuma mogući su različitim tehnikama, a primena lasera daje poseban kvalitet, poput visoke preciznosti obrade ili dobijanja specifičnih struktura na površini koje nije moguće generisati drugim metodama. Cilj ove doktorske disertacije je eksperimentalna optimizacija površinskog modifikovanja titanijuma impulsnim nano-, piko-, i femto-sekundnim laserima. Kao izvori laserskog zračenja korišćeni su nanosekundni CO2 laser, pikosekundni Nd:YAG, i femtosekundni Ti:safirni laser. Poznato je da stepen površinske modifikacije mete zavisi od parametara laserskog zračenja (talasne dužine, dužine trajanja impulsa, energije impulsa, itd.), od geometrije fokusiranja, od stanja površine i apsorptivnosti mete, kao i od sredine u kojoj se interakcija odvija. U cilju nalaženja optimalnih uslova za površinsku modifikaciju titanijuma ispitan je uticaj pojednih parametara lasera, kao i uticaj ambijenta. Utvrđeno je da primenjeni intenziteti laserskog zračenja dovode do modifikacija površine mete, pri čemu impulsi različitog trajanja drugačije modifikuju titanijumsku metu. Nanosekundni i pikosekundni laseri dovode do difuznog karaktera oštećenja uz prisustvo termalnih efekata, dok korišćenje femtosekundnih impulsa rezultuje u bolje definisanim oblastima oštećenja. Pokazano je da promena sredine ozračivanja presudno utiče na hemijski sastav i morfologiju površine mete. The interaction of lasers with metals has been studied for decades, and has been especially intensified lately, due to the development of new, efficient pulsed lasers. Research in this thesis is focused on titanium, which has a number of excellent properties, making it applicable in various modern technologies. Treatment and processing of titanium is possible with various techniques, and the application of lasers gives a special quality, such as high precision machining or obtaining specific structures on the surface which cannot be generated by other methods. The goal of this doctoral dissertation is the experimental optimization of surface processing of titanium by pulsed nano-, pico-, and femto-second lasers. Laser radiation sources used were nanosecond CO2 laser, picosecond Nd:YAG, and femtosecond Ti: sapphire laser. It is known that the degree of surface modification of the target depends on laser radiation parameters (wavelength, pulse duration, pulse energy, etc.), focus geometry, the state of the surface and the absorption of the target, as well as from the environment in which the interaction takes place. In order to find the optimal conditions for surface modification of titanium, the influence of certain laser parameters, as well as the influence of the ambient, was examined. It has been found that the applied laser radiation intensities lead to the modification of the target surface, and that the pulses of different duration modify the titanium target in various way. Nanosecond and picosecond lasers lead to a diffuse character of damaged area with the presence of thermal effects, while the use of femtosecond pulses results in better defined area of damage. It has been shown that the change in the ambient of the irradiation affects the chemical composition and morphology of the target surface.