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Od 19. do 21. svibnja 2023.na Zagrebačkom Velesajmu, u Paviljonu 10A, održano je drugo izdanje MUZZA Tjedna Znanosti. U sklopu MUZZA LAB- a održano je je šest radionica "Vodik na dlanu" koje su bile dobro posjećene. Radionice su održane u sklopu promicanja znanosti i Fakulteta kemijskog inženjerstva i tehnologije u STEM području pod nazivom "Mi vidimo nevidljivo". U radionici je pokazano kako je vodik moguće proizvesti elektrolizom vode i koristiti ga za pokretanje električnog automobila. Sudionici radionice su upoznati s važnosti korištenja obnovljivih izvora energije s ciljem ostvarivanja ekonomske i ekološke održivosti.

Titanium is a widely employed material in the aerospace industry, biomedicine and dentistry due to the combination of favorable mechanical properties, great corrosion resistance and good tissue compatibility. Some of the titanium properties are attributed to the passive oxide layer, which spontaneously forms on the titanium surface in an oxygen-containing environment. The protective oxide layer, few nanometers thick, mainly consists of amorphous TiO2. Many properties of titanium can be improved by introducing polyelectrolyte films on its surface. For example, polyelectrolyte coatings offer a new way for antibacterial protection of titanium dental implants. Properties of such films are controlled by the interplay of various interactions between surface and adsorbed polymer molecules. A comprehensive understanding of these interactions may enable very fine-tuning of titanium surface properties. In this study, the surface properties of Ti/TiO2 substrate before and after the adsorption of polyelectrolytes were investigated. As a model polyelectrolytes, strongly charged polycation poly(diallyldimethylammonium chloride) (PDADMA) and strongly charged polyanion poly(sodium 4- styrenesulfonate) (PSS) were used. First, the bare titanium substrate was characterized by means of ellipsometry, atomic force microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. It was shown that the substrate surface is very flat with an average roughness of only 2.3 nm and oxide layer thickness of 3.8 nm. Furthermore, electrochemical measurements revealed a good corrosion resistance of Ti/TiO2 substrate. After the adsorption of polyelectrolytes, coated titanium surface was again examined using the above-mentioned methods. Enhanced anticorrosion characteristics were observed for surfaces fabricated by both polyelectrolyte films, while the surface roughness didn't significantly change. These results lead us to the conclusion that polyelectrolyte molecules form a stable nanofilm on Ti/TiO2 surface that partially or fully covers the surface. Our previous work made on the adsorption of PSS to rutile surface strongly corroborates these findings.

In this study, TiO2 oxide layer on titanium was formed spontaneously (S) and potentiostatically in phosphate buffer solution (EC). It was shown by means of ellipsometry and atomic force microscopy, that the Ti/TiO2 surface is very flat with an average roughness of only 2.3 nm (S) and 3.4 nm (EC) and oxide layer thickness of 4.1 nm (S) and 16.1 nm (EC). The electrochemical properties and corrosion protective effectiveness were examined by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and single crystal electrode (SCrE). The CV indicates the behavior of the valve metals with the anodic formation of the barrier oxide film. The semiconducting properties were studied by Mott- Schottky analysis. A preponderance of anion vacancies, which act as electron donors, over cation vacancies within the passive film formed electrochemically, was established providing n- type semiconducting behavior of the film. The obtained EIS data were modelled utilizing electrical equivalent circuit. The corrosion protection effectiveness value of 94.7 % indicates that the corrosion properties were greatly enhanced upon modification by TiO2 oxide layer. The EIS results also indicate that the oxide film on the Ti surface consists of two layers, an inner barrier layer associated with higher impedance values and responsible for corrosion protection, and an outer porous layer characterized by lower impedance values and lower compactness.

Uslijed mehaničke traume, ozljede ili zbog nepravovremeno liječenog karijesa i paradontoze može doći do djelomičnog ili potpunog gubitka zuba/zubiju. Kako bi se održala kakvoća života pojedinca problem se rješava ugradnjom dentalnih implantata – metalni vijak, kao baza za keramičku krunicu, most ili zubnu protezu, ugrađuje se u kost čeljusti. Za izradu dentalnih implantata najčešće se koriste materijali na osnovi titanija. Za uspješnu implantaciju i kako bi se izbjegle bolne korekcijske operacije, po ugradnji implantata mora doći do brze oseointegracije s okolnom kosti i tkivima. Kako formiranje postojanih interakcija implantni materijal/kost i implatni materijal/okolno tkivo ovisi o mikrostrukturi, morfologiji i sastavu te hidrofilnosti površine, funkcionalizacija površine implatnog materijala je od ključne važnosti. U ovom istraživanju, provedena je funkcionalizacija površine titanijeva dentalnog implantata kemisorpcijom bioaktivnih molekula, mogućih pojačivača oseointegracije. Morfologija modificiranih površina Ti|TiO2|bioaktivna prevlaka ispitana je koristeći SEM, a svojstva močenja pomoću mjerenja kontaktnog kuta. In vitro karakterizacija nemodificiranih i modificiranih površina provedena je u otopini umjetne sline upotrebom elektrokemijske impedancijske spektroskopije. Eksperimentalna otkrića potvrđena su DFT izračunima i predložen je mehanizam formiranja bioaktivnih prevlaka.

Since implantation success strongly depends on the osseointegration process, current trends in dental implant research are based on surface properties modifications by biomimetic and bioactive coatings that mimic biochemical surroundings and architecture of the human bone. Calcium phosphate ceramics, like hydroxyapatite, with mineral composition similar to natural bone, as a single compound coating or as a composite with collagen, bioglass, or silica are used to promote osseointegration or overall implant system’s characteristics. Drug-based coatings with bisphosphonates like Zolendronate or Alendronate, drugs for bone diseases, promote mechanical fixation of implant and bone mineralization. However, it must not be forgotten that a fundamental prerequisite for the success of osseointegration is a long-term corrosion stability of implant materials. Human body fluids, especially oral cavity fluids, in which pH is constantly changing, represent very aggressive media with high concentrations of chloride ions that are among the most aggressive and corrosive to metals. Although titanium is a gold standard in dental implantology due to its exceptional biocompatibility and corrosion resistivity, there is an increasing data reported regarding complications caused by titanium dental implant fixation. It was shown that titanium ions, that originated as product from corrosion reaction in body fluids, caused negative immune reactions or skin allergies immediately or shortly after implant fixation. Therefore, it is crucial to design a coating which will make titanium surface more bioactive/osseoinductive and at the same time more corrosion resistant during a long-term exposure to oral cavity fluids. In this study the titanium surface was modified by vitamin D3, molecules that are crucial for maintaining bone mineral density and normal functioning of the immune system. The main goals were (i) to improve titanium corrosion resistivity during exposure to an artificial saliva solution and simultaneously (ii) to induce in vitro processes of “new bone” formation. According to results of all techniques, the D3 vitamin layer imparted very good corrosion protection to the oxide-covered titanium and induced a formation of biocompatible bone-like calcium phosphates what confirmed enhanced titanium's bioactivity level.

Although dental implants have been used since ancient times, there is a continuing need to improve characteristics to ensure their long- term integration into the jaw.^1 Current trends in dental implant research are focused on surface properties modification by biomimetic and bioactive coatings that mimic architecture of the human bone and biosurrounding.^2-4 Therefore, the titanium dental implant was functionalized by two different molecules, Cholecalciferol (vitamin D3) and Alendronate sodium (Fosamax®T). D3 vitamin and Alendronate were chosen due to their known positive influences on human organism, especially on the bone-system. The aim of functionalization was (i) to improve anti-corrosion properties of the implant and simultaneously (ii) make implant´s surface potentially more bioactive (to promote and accelerate osseointegration). An integrated experimental-theoretical approach was applied to study coating´s formation mechanism, wetting properties and corrosion behaviour in an artificial saliva solution (during 7 days). In general, the results indicate improved surface properties of the implant after functionalization and are in a direct corelation with chemical nature and structure of coating molecules.

Life inevitably leaves its traces on the teeth. A mechanical trauma, an accident or untimely treated caries and periodontitis frequently lead to permanent tooth loss. Dentists and dental specialists have a contemporary solution: the small titanium body fixed into the jawbone acts as the base for single crowns, larger bridges or dentures. Titanium dental implants, in the form of screw (endosseous implants), are various-age appropriate secure solution and are the most used implants. Since a dental implant, generally metal-made, represents a foreign body for the patient, many difficulties can occur. Therefore, for successful implant application, the dental industry has to consider all relevant factors that are related to dental reconstruction and restoration like biocompatibility, osseointegration, corrosion resistance, implant geometry design, mechanical stability, and implant/bone and implant/surrounding tissue interactions. Once the implant is placed within the jaw, it should rapidly osseointegrate with surrounding bones and tissues and create a stable implant/surrounding bone interface. It is clear, implant-bone and implant-surrounding tissue interactions are affected by the implant surface microstructure, composition, morphology, roughness and hydrophilicity. Hence, surface engineering plays a significant role in the improvement of the implantation process, especially osseointegration. Many studies report about surface modification of dental implants (e.g., sandblasting, acid etching, anodization, self-assembling etc.) in order to optimize and improve their surface characteristics and enhance implantation. In this study, the titanium implant surface was functionalized by chemisorption of osseoinductive molecule using a facile and effective approach. The morphology of the modified implant surface, Ti/TiO2/bioactive coating, was examined by SEM and wetting properties by contact angle measurements. Electrochemical properties of the Ti/TiO2/bioactive coating were studied in vitro in artificial saliva solution using electrochemical impedance spectroscopy. The experimental findings were corroborated by means of DFT calculations. The formation mechanism of bioactive implant coating was proposed considering experimental results and a computational study of Gibbs free energies of bioactive molecule/TiO2 molecular interactions.

Anorganski poluvodički spojevi prijelaznih metala u fokusu su interesa kao potencijalni fotokatalizatori u održivim tehnologijama konverzije energije i zaštite okoliša. Unatoč velikom broju istraživanja u području fotokatalize, još uvijek postoji problem dizajniranja fotokatalitičkih sustava visoke djelotvornosti za pročišćavanje voda. Za rješavanje problema potrebno je razviti koncept temeljem kojeg bi bilo moguće predložiti osmišljenu konstrukciju poluvodičkog fotokatalizatora s povećanom fotokatalitičkom učinkovitosti i stabilnosti samog fotokatalizatora u kontaktu s vodenim medijem. U ovom radu definirani su potrebni uvjeti koji osiguravaju uzajamnu povezanost između termodinamičkih karakteristika komponenata fotokatalitičkog sustava i energetske kompatibilnosti procesa u kojima se dobivaju slobodne radikalske vrste nužne za odvijanje fotokatalitičkih procesa degradacije organskih polutanata. S namjerom razvoja toga koncepta konstruirani su energija-vrpce dijagrami, za poluvodički fotokatalizator n-Bi2S3 i ko- katalizator n-Bi2O3, koristeći rezultate poluvodičkih parametara dobivenih Mott-Schottky i Kubelka-Munk analizom. Zašto ko-katalizator? Pri osvjetljavanju fotokatalizatora Bi2S3, koji uz širinu zabranjene zone od 1.4 eV apsorbira u vidljivom dijelu Sunčevog spektra, paralelno s fotokatalitičkom pretvorbom organskih polutanata do željenih produkata, odvijaju se i deaktivacijski procesi. Kako bi se spriječili ti neželjeni procesi, kao što je rekombinacija svjetlom generiranih elektrona i šupljina, fotokatalitički sustav mora biti kompleksniji. Stoga je kao ko-katalizatorski materijal korišten Bi2O3, poluvodič široke zabranjene zone od 2.8 eV koji može sudjelovati u tamnom periodu fotokatalitičkog procesa. Deaktivacija katalizatora izbjegnuta je prijelazom elektrona između vodljivih vrpci poluvodičkog katalizatora i ko-katalizatora.

The oxide film (TiO2) was formed on Nitinol potentiostatically in an acetic acid solution. Deep understanding of electronic properties of this film is needed to predict long-term corrosion properties of Nitinol implant material in simulated body fluid conditions. The capacitance measurements were performed under depletion conditions to study electronic (semiconducting) properties. The space charge, formed at the solid|liquid interface, creates the barrier for the corrosion processes in aggressive (bio)environment. According to the results of electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis (MS), the passive film on Nitinol behaves as amorphous highly-doped n-type semiconductor. The values of electronic structure parameters (the flat-band potential, Efb and the carrier (donor) density, ND) were corrected for frequency dispersion.

Various surface modifications have been applied to titanium and titanium alloys implants to improve their corrosion resistance and biocompatibility1. In this work Nitinol surface was modified with bioactive, bone-like hydroxyapatite coatings(HA), obtained by two deposition steps: electrochemical and chemical. Each of them has individual formation mechanism and deposited films posses different protection and biocompatible (bioactive) properties. The kinetics of the first step, nucleation of HA precursor film, was studied in situ using chronoamperometry (CA) and cyclic voltammetry (CV). The morphology, microstructure and barrier properties of HA coatings were characterized by field emission scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The chemical composition was examined using energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR).

Occlusive coronary artery disease (CAD) is reported to be the single largest cause of death in developed countries, such as Canada and United States. The disease is characterized mostly by the formation of a plaque, resulting in considerable narrowing and hardening of the vessels. Stenting following percutaneous transluminal balloon angioplasty has proved to be the less invasive treatment for CAD. Nitinol, a roughly equiatomic alloy of nickeltitanium, has been used extensively in biomedical devices, particularly in cardiovascular stents, due to its outstanding mechanical characteristics, such as the ability to remember its original shape. However, all current bare-metal stents, including Nitinol, offer low biocompatibility. This results in occurrence of in-stent restenosis in up to ca. 30% patients, and the need for further medical treatment. Therefore, various stent-surface modification approaches have been employed in order to minimize in-stent restenosis, but none of them have proven to give long-term satisfactory benefits. Furthermore, one the major concerns of using Nitinol in cardiovascular stents is the release of nickel ions to the body, which has proved to be carcinogenic and allergic. Thus, the aim of this work was to develop a new method for the Nitionol (stent) surface functionalization, with the ultimate goal decreasing the in-stent restenosis rate. We functionalized a Nitinol surface with a phosphonic acid self-assembled monolayer (SAM) which not only acts as a surface corrosion inhibitor that minimizes the nickel ions release to the human body, but also potentially enable us to further functionalize the surface with a (bio)molecule of choice, such as proteins and drugs.