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International audience; Hybrid nanocomposites containing Carbon nanotubes (CNT) and inorganic nanoparticles produce new properties due to interfacial effectsabsent in the individual nanomaterials. ZnO is a well-known semiconductor. Conversely, HfO2 is a wide bandgap dielectric. When reduced to nanoparticles with average sizes of 2.6nm, they emanate in the blue-green part of the visible spectrum. This is attributed to surface defects generated due to size reduction, which in turn create luminescent defect states within the band gap of HfO2. In both cases, i.e. ZnO and HfO2, the oxygen vacancy related emission is between 2.3 and 2.5eV. Both materials also emit at approximately 3.3eV. In ZnO, the emission at 3.27eV corresponds to the near band edge emission (NBE), while as in HfO2 it corresponds to the Hf3+ defects states. When combined with CNT, changes in the emission spectra are observed producing new phenomena. In the case of HfO2-CNT, both visible and UV photoexcitations are capable of producing a photocurrent at zero bias. This advocates its applicability as an active layer in photovoltaic cells. Depending on the photoexcitation, different defectstates participate in the generation of photocurrents. Furthermore, Ag nanoparticles can act as nano-antennas owing to their plasmonic effect and the addition of Ag nanoparticles to ZnO-CNT demonstrates that the optical bandgap of the nanocomposites increases due to the Burnstein-Moss effect. Thus,conjoining Ag to ZnO-CNT not only enhances the UV emission but also suppresses the visible emission. For highly defective ZnO, addition of Ag nanoparticles allows visiblelight activation of ZnO-CNT-Ag nanohybrids. This talk will cover the synthesis and optical properties of the nanohybrids.In addition, a modified common multimeter capable of measuring nanocurrents from HfO2-CNT will be briefly presented.

Erwan Rauwel1 ,* Siham Al-Arag2 ,* Hamideh Salehi,2 Carlos O Amorim,3 Frédéric Cuisinier,2 Mithu Guha,4 Maria S Rosario,5 Protima Rauwel1 1Institute of Technology, Estonian University of Life Sciences, Tartu, Estonia; 2LBN, University of Montpellier, Montpellier, France; 3Dpt. Of Physics & CICECO – Aveiro Institute of Materials, University of Aveiro, Aveiro, Portugal; 4Dpt. Of General & Molecular Pathology, Faculty of Medicine, University of Tartu, Tartu, Estonia; 5CICECO – Aveiro Institute of Materials, University of Aveiro, Aveiro, Portugal*These authors contributed equally to this workCorrespondence: Erwan Rauwel Email erwan.rauwel@emu.eePurpose: Nanotechnology applied to cancer treatment is a growing area of research in nanomedicine with magnetic nanoparticle-mediated anti-cancer drug delivery systems offering least possible side effects. To that end, both structural and chemical properties of commercial cobalt metal nanoparticles were studied using label-free confocal Raman spectroscopy.Materials and Methods: Crystal structure and morphology of cobalt nanoparticles were studied by XRD and TEM. Magnetic properties were studied with SQUID and PPMS. Confocal Raman microscopy has high spatial resolution and compositional sensitivity. It, therefore, serves as a label-free tool to trace nanoparticles within cells and investigate the interaction between coating-free cobalt metal nanoparticles and cancer cells. The toxicity of cobalt nanoparticles against human cells was assessed by MTT assay.Results: Superparamagnetic Co metal nanoparticle uptake by MCF7 and HCT116 cancer cells and DPSC mesenchymal stem cells was investigated by confocal Raman microscopy. The Raman nanoparticle signature also allowed accurate detection of the nanoparticle within the cell without labelling. A rapid uptake of the cobalt nanoparticles followed by rapid apoptosis was observed. Their low cytotoxicity, assessed by means of MTT assay against human embryonic kidney (HEK) cells, makes them promising candidates for the development of targeted therapies. Moreover, under a laser irradiation of 20mW with a wavelength of 532nm, it is possible to bring about local heating leading to combustion of the cobalt metal nanoparticles within cells, whereupon opening new routes for cancer phototherapy.Conclusion: Label-free confocal Raman spectroscopy enables accurately localizing the Co metal nanoparticles in cellular environments. The interaction between the surfactant-free cobalt metal nanoparticles and cancer cells was investigated. The facile endocytosis in cancer cells shows that these nanoparticles have potential in engendering their apoptosis. This preliminary study demonstrates the feasibility and relevance of cobalt nanomaterials for applications in nanomedicine such as phototherapy, hyperthermia or stem cell delivery.Keywords: Raman spectroscopy, cobalt nanoparticles, cancer cells, stem cells, cellular uptake, apoptosis, label-free tool

International audience

International audience

Photoluminescent ZnO carbon nanomaterials are an emerging class of nanomaterials with unique optical properties. They each, ZnO and carbon nanomaterials, have an advantage of being nontoxic and environmentally friendly. Their cost-effective production methods along with simple synthesis routes are also of interest. Moreover, ZnO presents photoluminescence emission in the UV and visible region depending on the synthesis routes, shape, size, deep level, and surface defects. When combined with carbon nanomaterials, modification of surface defects in ZnO allows tuning of these photoluminescence properties to produce, for example, white light. Moreover, efficient energy transfer from the ZnO to carbon nanostructures makes them suitable candidates not only in energy harvesting applications but also in biosensors, photodetectors, and low temperature thermal imaging. This work reviews the synthesis and photoluminescence properties of 3 carbon allotropes: carbon quantum or nanodots, graphene, and carbon nanotubes when hybridized with ZnO nanostructures. Various synthesis routes for the hybrid materials with different morphologies of ZnO are presented. Moreover, differences in photoluminescence emission when combining ZnO with each of the three different allotropes are analysed.

Silver has been recognized as a nontoxic, safe inorganic antibacterial/antifungal agent used for centuries. Silver demonstrates a very high potential in a wide range of biological applications, more particularly in the form of nanoparticles. Environmentally friendly synthesis methods are becoming more and more popular in chemistry and chemical technologies and the need for ecological methods of synthesis is increasing; the aim is to reduce polluting reaction by-products. Another important advantage of green synthesis methods lies in its cost-effectiveness and in the abundance of raw materials. During the last five years, many efforts were put into developing new greener and cheaper methods for the synthesis of nanoparticles. The cost decrease and less harmful synthesis methods have been the motivation in comparison to other synthesis techniques where harmful reductive organic species produce hazardous by-products. This environment-friendly aspect has now become a major social issue and is instrumental in combatting environmental pollution through reduction or elimination of hazardous materials. This review describes a brief overview of the research on green synthesis of silver metal nanoparticles and the influence of the method on their size and morphology.

Bachelor’s thesis Curriculum in Engineering The study of the transmittance and absorbance properties of a material in the design of solar cells is of significant importance. The transmittance of a material determines the ability of light to pass through it. Whereas, the absorbance of a material determines its ability to absorb light. ZnO nanostructures are a good choice for such properties as several studies have shown that ZnO nanostructures show high transmittance (~80%). Also, ZnO nanostructures can absorb most of the UV region of light coming from the sun. In this thesis, the transmittance and absorbance properties of four different types of ZnO nanorod samples were investigated, each of which was prepared with different solvents. The solvents used are ethanol, 70% ethanol, methanol, and isopropanol. A UV-1600PC spectrophotometer was used for measuring the transmittance and absorbance of ZnO nanorod samples. Two types of reference materials were used for the measurements. The results obtained based on the transmittance and absorbance measurements are analysed and compared. Finally, the bandgaps for each of the synthesized nanorods were calculated by using the Tauc relation, and the optimal ZnO nanorod sample for solar cell applications was discussed. Materjali läbilaskvuse ja neeldumisvõime omaduste uurimine on päikesepatareide projekteerimisel väga oluline. Materjali läbilaskvus määrab valguse läbilaskvuse läbi materjali. Materjali neelduvus määrab, kui palju valgust materjal suudab neelata. ZnO nanostruktuurid on selliste omaduste poolest hea valik, sest mitmed uuringud on näidanud, et ZnO nanostruktuuridel on kõrge läbilaskvus (~80%). Samuti suudavad ZnO nanostruktuurid absorbeerida enamiku päikesest tuleva valguse UVkiirguse piirkonnast. Käesolevas lõputöös uuriti nelja erineva ZnO nanostruktuuride proovi läbilaskvus ja neeldumisomadusi, millest igaüks valmistati erinevate lahustite abil. Kasutatud lahustid on etanool, 70% etanool, metanool ja isopropanool. ZnO nanovarraste proovide läbilaskvuse ja neelduvuse mõõtmiseks kasutati UV-1600PC spektrofotomeetrit. Mõõtmistes kasutati kahte tüüpi võrdlusmaterjale. Analüüsitakse ja võrreldakse läbilaskvuse ja neelduvuse mõõtmiste põhjal saadud tulemusi. Viimasena arvutati iga sünteesitud nanovarda ribalõhed Tauci suhte abil ja toodi välja ZnO nanovarraste parem valik päikesepatareide kasutamiseks.

Bachelor’s thesis Engineering Lithium-ion batteries are critical for the EU’s energy transition, but their current energy capacity is insufficient. Tin oxide (SnO₂) nanomaterials, as a semiconductor with a bandgap of 3.6 eV (electron volt), can improve the electrochemical properties of Li-ion batteries, by increasing their lifespan and resolving low energy capacity issues. Electronic properties such as bandgap are linked to synthesis conditions. The main goal of this bachelor's thesis is to determine the bandgap of five different samples of SnO₂ nanomaterials using UV-visible spectroscopy to investigate the effect of temperature and synthesis time on their electronic properties. Using a Tauc plot of the UVvisible spectra, bandgaps are determined. Temperature and synthesis time show a variation in the indirect bandgap but no significant impact on the direct bandgap. Defect states of SnO₂ can be seen in the visible absorption spectra. As the synthesis time increases, more defects are created in the material. This might be caused by different nanomaterial sizes, shapes, phases, or compositions; however, due to the lack of information, no conclusion can be drawn. Further investigation is needed to understand these bandgap variations. The future electrochemical analysis will make it possible to correlate the synthesis conditions with electronic and electrochemical properties, resulting in the best nanomaterials for battery applications. Liitiumioonakud on Euroopa Liidu energiasüsteemi ümberkujundamisel üliolulised, kuid nende praegune energiamahutavus on ebapiisav, seetõttu on vaja leida uusi lahendusi. Üheks võimaluseks on kasutada tina oksiidi (SnO₂) nanomaterjale, mis on pooljuhid ja tsooniteooria kohaselt on nende keelutsooni energia 3.6 eVi (elektronvolt). See võimaldab parandada liitiumioonakude elektrokeemilisi omadusi, pikendades nende eluiga ja suurendades energiamahutavust. Oluline on leida õiged SnO₂ sünteesimistingimused, mis on seotud elektrooniliste omadustega, sealhulgas keelutsooni energiaga. Käesoleva bakalaureusetöö peamine eesmärk on UV-spektroskoopia abil määrata viie erineva SnO₂ nanomaterjali keelutsooni energia ja uurida seeläbi temperatuuri ja sünteesiaja mõju nende elektroonilistele omadustele. UV spektri tulemuste põhjal analüüsiti Tauc arvutusmeetodil saadud tulemusi, kus ei avaldu otsese keelutsooni olulisi erinevusi, kuid kaudne keelutsoon näitab varieerumisi, mis võib olla tingitud nanomaterjalide erinevast suurusest, kujust, faasist või koostisest. Uurides SnO₂ defektiseisundeid nähtavas neeldumisspektris sünteesiaja suurenedes näitab, et pikema sünteesiajaga tekib materjalis rohkem defektitasandeid. Selleks, et mõista ja selgitada välja, mis põhjustab seesuguseid keelutsooni muutusi ja materjali defekte, tuleks teostada edasisi uuringuid. Tulevikus tehtav elektrokeemiline analüüs võib võimaldada korrelatsiooni elektrooniliste- ja elektrokeemiliste omaduste ning sünteesitingimuste vahel, võimaldades seeläbi toota optimaalseid nanomaterjale, mida saame kasutada liitiumioonakude edasiseks arendamiseks.

Bachelor’s thesis Engineering Curriculum Green or sunlight-driven photocatalysis and photovoltaics are environmental-friendly methods for the productions of fuels and electricity, respectively. The aim of this thesis is to use UV-Vis spectroscopy to analyze the optical properties of copper (Cu)-based nanoparticles in order to study their capability of absorbing light in the visible part of the solar spectrum and evaluate them as candidates for green energy production. Cu-based nanoparticles have good optical, electronic and catalytic properties and small band gaps of 1.4-2.5 eV for Cu2O and 0.8-1.9 eV for Cu3N, making them potentially effective materials for the production of energy. Herein, the absorption properties, band gaps and photocatalytic characteristics of four samples synthesized with different stirring time (20 min, 2 h, 3h and 5 h) using a non-aqueous sol-gel method, were investigated using UVVis spectroscopy. Results were plotted and analyzed using the OriginPro software. The result suggests that all the samples are sensitive to solar radiation. However, the best material for green energy production is the one containing the highest quantities of Cu3N with an absorption range extending up to the near infrared region. Päikesevalgusest juhitud fotokatalüüs ja fotogalvaanika on keskkonnasõbralikud meetodid kütuste ja elektri tootmiseks. Käesoleva lõputöö eesmärgiks on analüüsida vasepõhiste nanoosakeste optilisi omadusi, et uurida nende võimet neelata valgust päikesespektri nähtavas osas ning hinnata neid rohelise energia allika kandidaatidena. Vasepõhistel nanoosakestel on head optilised, elektroonilised ja katalüütilised omadused ning kitsas keelutsoon, mis jääb Cu2O puhul vahemikku 1.4-2.5 eV ja Cu3N puhul vahemikku 0.8-1.9 eV, mistõttu on need potentsiaalselt tõhusad materjalid energia tootmiseks. Mittevesilahusel põhineval sool-geel meetodil sünteesiti nelja erineva segamisajaga (20 m, 2 h, 3 h ja 5 h) vasepõhiste nanoosakeste proove. Saadud proove uuriti seejärel kasutades UV-Vis spektromeetrit. Tulemused kanti graafikule ning analüüsiti kasutades tarkvara OriginPro. Tulemustest saab järeldada, et kõik proovid neelavad valgust silmale nähtavas spektri ulatuses. Siiski, parim materjal rohelise energia tootmiseks sisaldab suures koguses Cu3N nanoosakesi ning neelab valgust ka spektri lähiinfrapuna piirkonnas.

Master’s Thesis Energy Application Engineering Curriculum In this study, electrical and photoelectrical properties of ZnO nanorods were investigated. This study is the continuation of my bachelor’s work where I studied absorption and band gap properties of ZnO nanoparticles. The aim of the current study was to investigate electrical properties of ZnO nanostructures. It was found that ZnO nanoparticles studied in my bachelor’s do not show electrical characteristics due to high amount of grain boundaries and non-uniformity. Therefore, the nanorods structure of ZnO was investigated for the electrical measurements. In this study, four samples of ZnO nanorods were investigated, and are classified according to the solvent used for preparing the seeding layer. The nanorods were prepared by a two-step method. The first step includes seeding of zinc precursor. The seeding solution was prepared in four different solvents: ethanol, methanol, isopropanol and 70% ethanol. The second step was the hydrothermal method to grow ZnO nanorods on pre-seeded indium tin oxide (ITO) substrate. The ITO substrate, which consists of 100 nm thick ITO layer deposited on 0.5 mm thick quartz glass substrate were purchased from Ossila [1]. The current-voltage (I-V) characteristics of all four ZnO nanorod samples were studied for two types of contacts: Ohmic and Schottky. The measurements were carried out in two different conditions: in dark and under light exposure, for both type of contacts. A source measure unit (SMU) was used to measure ZnO nanorods conductivity. The measurement range was set to -3 V to +3 V for both Ohmic and Schottky contacts. The data was plotted with Origin Pro software. The Ohmic I-V measurements in dark and room light suggested that methanol seeded ZnO nanorod sample is highly photosensitive to room light itself. The experiments with Schottky behavior were not conclusive for all the nanorod samples. However, sample with isopropanol seeding showed Schottky-like characteristics for the silver (Ag) Schottky contact. The study of Schottky contact needs further investigations and is beyond the scope of this thesis. In conclusion, the enhancement in the current under room light for ohmic contacts for all the nanorod samples suggested that these samples are sensitive to photons emitted by room light. It was expected that room light emits some UV radiation coming from the neon light that excites electrons from ZnO nanorods and resulted in the enhancement of current. As mentioned earlier, the highest enhancement was shown by ZnO nanorods with methanol solution seeding, which suggests that this sample is a good UV light absorber compared to others and is a potential candidate to be used in applications such as solar cells and photo detectors. Käesolevas magistritöös uuriti ZnO nanovarraste elektrilisi ja fotoelektrilisi omadusi. See töö on jätkuks minu bakalaureusetööle, kus ma uurisin ZnO nanoosakeste valguse neeldumist ja selle energia vahemikke. Antud teadustöö eesmärk oli uurida ZnO nanostruktuuride elektrilisi omadusi ja valgustundlikkust. Selgus, et minu bakalaureusetöös uuritud ZnO nanoosakesed ei näita elektrilisi omadusi kasutusmeetodil uurides. Seetõttu sai valitud uurimisobjektiks ZnO nanovardad, et teostada valguse mõju tuvastamiseks vajalikke elektrimõõtmisi. Käesolevas töös uuriti nelja ZnO nanovarraste proovi, mis on klassifitseeritud vastavalt sünteesi aluskihi valmistamiseks kasutatud lahustile. Nanovardaid valmistati kaheastmelisel meetodil. Esimene samm hõlmas tsinki sisaldava sünteesi aluskihi valmistamist. Aluskihi tekitamiseks kasutatav lahus valmistati neljas erinevas lahustis: etanool, metanool, isopropanool ja 70% etanool. Teiseks etapiks oli hüdrotermiline meetod: ZnO nanovarraste kasvatamine eelnevalt kaetud indiumtinaoksiidiga (ITO) substraadil. 100 nm paksuse ITOkihtiga on kaetud 0,5 mm paksune kvartsklaasi tükk. Substraat osteti Ossilalt [1]. Kõigi nelja ZnO nanovarraste proovi voolu ja pinge (I-V) omadusi uuriti kahe tüüpi kontaktide puhul: Ohmic ja Schottky. Mõlema kontakti tüübi mõõtmised viidi läbi kahes erinevas olukorras: pimedas ja valguse käes. ZnO- nanovarraste juhtivuse mõõtmiseks kasutati mõõteseadet Source measure unit X200 (SMU). Mõõtmisvahemikuks määrati -3 V kuni +3 V nii Ohmickui ka Schottky-kontaktide puhul. Andmetöötlus sai tehtud Origin Pro tarkvaraga. Ohmic IV mõõtmised pimedas ja toavalguses näitasid, et metanooliga sünteesitud ZnO nanovarraste proov on toavalgusele väga valgustundlik. Katsed Schottky kontaktidega polnud kõigi nanovarraste proovide puhul veenvad. Isopropanooli proov näitas ainsana paremaid Schottkytaolisi omadusi hõbeda (Ag) Schottky- kontaktidega. Schottky- kontaktide uurimine vajab täiendavaid uuringuid ja väljub käesoleva lõputöö raamidest. Kokkuvõtteks võib öelda, et toavalguses toimuv voolu suurenemine kõigi nanovarraste proovide Ohmic kontaktide puhul viitas sellele, et need on tundlikud toavalguse poolt kiiritatud footonite suhtes. Eeldasin, et toavalgus kiirgab neoon valgust ja vähesel määral ka UV-kiirgust, mis ergastab ZnO nanovarraste elektrone ja põhjustas voolu suurenemise. Nagu varem mainitud, näitas kõige suuremat muutust metanooliga sünteesitud ZnO nanovardad. Antud proov on teistega võrreldes hea neoon valguse ja UV-kiirguse neelaja ja potentsionaalne kandidaat kasutamiseks päikesepaneelide ja fotodetektorite rakendustes.

Bakalaureusetöö Tehnika ja tehnoloogia õppekaval Silicon dioxide, or silica (SiO2) is a combination of chemical elements silicon (Si) and oxygen (O2). It is a very widespread material on Earth mainly in form of quartz and silica sand. Silicon dioxide is used in silicon solar cells on pure silicon wafers for surface passivation and antireflection. Surface passivation is a technique for preventing efficiency losses. Silicon dioxide has a bandgap energy from 7.52 to 9.6 eV (electron volt) depending on Si-O-Si bond angle and lengths. The aim of this Bachelor´s thesis is to analyse four different SiO2 nanoparticle samples synthesized at the Institute of Technology under UV-Vis spectrophotometer in order to find most UV and daylight absorption. The simplified model based on Beer-Lambert law was implemented to describe absorption in these silicon dioxide nanoparticle suspensions. As a result, the optical properties of these silicon dioxide nanoparticles were analysed in software named “Origin” and graphs interpreted. Conducted tests results may help to understand these SiO2 samples more. Käesoleva töö eesmärk on analüüsida erinevaid sool-geel meetodil Eesti Maaülikooli Tehnikainstituudis sünteesitud ränidioksiidide proove UV-Vis spektromeetri abil. Ränidioksiid (SiO2) on keemiliste elementide räni (Si) ja hapniku (O2) kombinatsioon. See on Maal väga laialt levinud materjal peamiselt kvartsi ja liiva kujul. Ränidioksiidi kasutatakse dopeeritud pooljuhtelement räniplaatide katmiseks päikesepaneelide fotogalvaanilistel elementidel. See väldib pooljuhtelemendi räni oksüdeerumist ning ühtlasi kaitseb seda väliskeskkonna mõjude eest. Samuti kasutatakse ränidioksiidi valguse peegeldumise vähendamiseks või siis soovitud peegeldumise saavutamiseks kombinatsioonis ainetega, millel on erinev refraktsiooniindeks. Puhta amorfse pooljuhtelemendi ränipinna passiveerimine võimaldab säilitada, tõsta fotogalvaanilise elemendi kasutegurit ning vähendada võimalikke kadusid. Tsooniteooria kohaselt on ränidioksiidi keelutsoon lai. SiO2 keelutsooni energia (valentsitsooni ja juhtivustsooni vahe) on vahemikus 7,52 kuni 9,6 eV (elektronvolt), mis sõltub Si-O-Si sidemenurgast ja pikkustest. Iga SiO2 proovi jaoks tehti lihtsustatud arvutused, kasutades Beer-Lamberti seadust. UV-Vis spektromeetri abil saadud tulemusi analüüsiti tarkvaras nimega “Origin” ja joonestati neeldumisgraafikud. Läbiviidud proovide analüüsi tulemused võivad aidata neid SiO2 proove paremini mõista.

Bachelor’s thesis Engineering / tech and technology curriculum, energy application management Solar cell technology is an ever-increasing field. Plasmonics is an upcoming heavy-hitter in this area. AgNPs play a role in plasmonics. It is in this thesis that AgNPs and their role in solar cells are looked into. Notions such as LSPR and pertaining phenomena are looked at. AgNPs samples have been provided of which UV-Vis Spectroscopy was performed, and samples measured. Theoretical details and the validity of information and details are analyzed. Absorption spectra analyzed with minute particle morphology analysis. Päikesepaneelide tehnoloogia on lai uurimisvaldkond. Plasmoonika on kindel liituja selles valdkonnas. AgNP-del või hõbemetallnanoosakestel on osatähtsus selles valdkonnas. Selles töös uuritakse AgNP-sid, nendega seotud nähtusi sh plasmon- või valgusresonants, ja nende rolli päikesetehnoloogias. Samuti on mõõdetud ning analüüsitud kolme AgNP proovi valguskiirguse neeldustugevust. On võrreldud teoreetiliste pooltega ning eripäradega. On analüüsitud osakeste morfoloogia ning muu osakaalu resonantstipu muutmisel.

Bachelor’s Thesis Engineering curriculum In this thesis the absorbance and band gap properties of ZnO nanoparticles (NP), which is a solar cell and photocatalytic material, have been investigated. The absorbance of the ZnO NP were measured using a UV-Vis spectrophotometer and their band gap properties were calculated. Four different samples of ZnO NP were already synthesized. Several steps after synthesis of these NP were carried out before obtaining a powder of ZnO NP, explained in this thesis. To measure the absorbance of these nanomaterials, ZnO NP were spread homogeneously in isopropanol. For absorbance studies, a UV-Vis II Nanocolor spectrophotometer by MACHEREY-NAGEL was used to measure the absorbance with a measurement range of 190–1100 nm. Isopropanol was also used as reference during the measurements. The UV-Vis spectrophotometershows the maximum absorbance of these ZnO NP in 356.8-363.1 nm range. All the results were plotted using software Origin and MS Excel. Energy band gaps were calculated using tauc plot method. The calculated band gap of ZnO NP were in 3.160-3.288 eV range which is comparable with the direct bandgap 3.37 eV of bulk ZnO. These variations in band gap are attributed to the synthesis conditions of these NP. Selles lõputöös uuriti valguse energia neeldumist ZnO nanoosakestes. Mõõdetud valguse neeldumist ja spektri vahemikke võrreldi kirjanduses olevaga. ZnO nanoosakesed olid juba eelnevalt valmistatud sünteesi teel. ZnO nanoosakesi oli 4 erinevat proovi. Töö alguses olid ZnO nanoosakesed teralise struktuuriga ja vajasid purustamist. Peale purustamist jäi alles väga peene pulber nanoosakestest. Purustamine võttis aega kuni 20 minutit. Valguse neeldumise mõõtmiseks oli vaja teha ZnO nanoosakeste lahus, lahustiks oli isopropanool. Neeldumise mõõtmiseks kasutati spektrofotomeetrit UV-Vis II Nanocolor tootjalt MACHEREY-NAGEL. Valguse neeldumine oli mõõdetav 190-1100 nm vahemikus. Spektrofotomeeter võimaldas 2 täpsusel mõõtmist: normaalne ja maksimaalne. Kõik mõõtmised siin töös said tehtud maksimaalsel režiimil, andmed olid palju täpsemad. Mõõdetud neeldumise suurimad väärtused jäid 356.8 ja 363.1 nm lainepikkuse vahemikku. Saadud andmeid töödeldi tarkvaraga Origin ja MS Excel. Kasutades tauc plot meetodit arvutati energia vahemik. Energia vahemik oli 3.160-3.288 eV, mis on võrreldav kirjanduses leitava ZnO energia vahemikuga 3.37 eV-ga.

Master's thesis Energy Application Engineering With the accelerating development in the world, there is a greater need to be mobile. As a result, there is an increased need for vehicles that run on internal combustion engines that use fossil fuels, which in turn are harmful to the environment. Nevertheless fossil fuels are necessary and increasing the efficiency of combustion engines has therefore become a priority. Therefore, the aim of the study was to investigate the effect of ZnO nanoparticle on diesel fuel on the fficiency of diesel motors. In the framework of this work, data has been collected from existing surveys on the Internet. All the experiments discussed in the work and their test results have been performed in the laboratories of the Technical Institute of the Estonian University of Life Sciences. Analysis of the experimental data showed that 10 mg of zinc oxide nanoparticles had no significant effect on diesel fuel. Nevertheless, reports in the literature have shown that nanoparticles increase the overall efficiency of combustion engines, therefore this research opens new perspectives for future works. Maailma üha kiireneva arenguga on tekkinud suurem vajadus olla mobiilne. See tõttu on suurenenud vajadus sõidukitele, mis töötavad sisepõlemis mootoritega, mis kasutavad fossiilkütuseid, mis omakorda on kahjulikud meid ümbritsevale keskkonnale. Töö eesmärgiks oli uurida missugust mõju avaldab ZnO nanoosakene diiselkütusele. Antud töö raames on tehtud andmete kogumine internetist olemasolevatest uuringutest. Kõik töös käsitletavad katsed ning nende katsetulemused on teostatud Eesti Maaülikooli Tehnikainstituudi laborites. Katseandmeid analüüsides selgus, et 10mg tsinkoksiid nanoosakestel ei olnud märgatavat mõju diislikütusele. Andmete analüüsile antakse ka soovitusi järgnevateks uurimistöödeks.

Master's thesis Energy Application Engineering The goal of this Master's thesis was to create a prototype setup in order to measure the photocurrent generated by hybrid nanocomposites like HfO2-carbon nanotube based (CNT). The specifications of the setup were to illuminate a sample with UV and visible light and to be able to measure photocurrent of a few nano-ampere using a conventional multimeter. No portable device for such research activity with the required components and specifications is available presently. It was demonstrated in a previous study, that 1 mg of the nanohybrid can, under strong illumination, produce a photocurrent of about 150 nA, which is on the resolution limit of most multimeters. The study aimed at obtaining current values with high accuracy with two different multimeters available at EMÜ. This was brought about by building a circuit with an operational amplifier that amplifies the voltage drop on a shunt resistor. The resulting voltage is measurable in mV range and corresponds to nA scale of the amplifier input. Four prototypes were developed, and the final prototype has a lighting unit with 339 W/m2 power output and current measurement resolution of 0,01 nA. An integral part of the prototype development was the mitigation of interferences, which were brought down from 50 nA to 1,7 nA. Selle magistritöö eesmärk oli luua prototüüpseade nanohübriidmaterjalide, nagu HfO2- süsinik-nanotorud (CNT), poolt tekitatud fotovoolu mõõtmiseks. Seadme ülesandeks oli valgustada nanohübriidmaterjali proovi ultraviolett- ja nähtava valgusega ning tavapärase multimeetri abil mõõta mõne nanoampri suurust fotovoolu. Praegu teada olevalt ei ole sellise uurimistegevuse jaoks kaasaskantavaid seadmeid koos vajalike komponentide ja spetsifikatsioonidega saadaval. Ühes eelnevas uuringus tuvastati, et 1 mg nanohübriidmaterjali võib tugeva valgustatuse korral tekitada fotovoolu umbes 150 nA, mis on enamiku multimeetrite lahutusvõime piiril. Uuringu eesmärk oli mõõta nanoamprite suurusjärgus voolu kahe erineva tehnilise tasemega EMÜ-s saadaoleva multimeetri abil. Selle saavutamiseks koostati operatsioonivõimendiga vooluahel, mis võimendab šunttakisti pingelangu, mida saab mõõta multimeetri mV pingevahemikus ja mis vastab võimendi sisendi nA väärtusele. Seadme arendusfaasis valmisid neli prototüüpi ja lõplikul prototüübil on valgustusseade, mille väljundvõimsus on 339 W / m2 ning voolu eraldusvõime 0,01 nA. Prototüübi väljatöötamise lahutamatu osa oli häirete vähendamine, mille käigus vähendati neid 50 nA pealt 1,7 nA peale.

Magistritöö Vesiehituse ja veekaitse õppekaval Eestis on suured põhjaveevarud, mille üldine seisund on hea, kuid olmeveena kasutamise üheks põhiprobleemiks on suur rauasisaldus. Koos rauaga esineb põhjavees sageli ka mangaan, mis esinevad mõlemad põhjavees lahustunud kujul. Töö eesmärgiks oli laborkatsete abil uurida tavapäraste ja nanoühenditega kaetud filtermaterjalide tõhusust raua ja mangaani eemaldamiseks põhjaveest. Ühtlasi taheti ka välja selgitada, kas uuritavad filtermaterjalid on võimelised rauda ja mangaani põhjaveest eemaldama Eestis kehtestatud kvaliteedinõuetele joogivees. Käesolevas töös uuriti seitset erinevat katsekeha. Tulemustest selgus, et katseseeriates käsitletud katsekehade kohta näitas parimaid tulemusi põhjaveest raua eemaldamisel katsekeha F-3, mis koosnes suuremas osas nanomaterjalidega täiustatud filtermaterjalist. Samuti näitas katsekeha F-3 kõige lubavamat tulemust mangaani eemaldamises põhjaveest. Katsekehadega tuleks teha täiendavaid uuringuid, suurendades filtreeritava põhjavee ja katsekehades olevate filtermaterjalide kogust. Estonia has large groundwater resources, the general condition of which is good, but one of the main problems in using it as domestic water is the high iron content. Along with iron, groundwater often contains manganese, both of which are present in dissolved form in groundwater. The aim of the work was to experimentally determine the advantages of surface-treated metallic nanomaterials over conventional filter material for the removal of iron and manganese in groundwater. It was also wanted to find out whether the studied filter materials were able to remove iron and manganese from groundwater up to the limits established in Estonia. In this work, seven different filters were studied. The results showed that among all test experiments, filter F-3, which consisted mostly of filter material enhanced with nanomaterials, showed the best results in removing iron from groundwater. Filter F-3 also showed the most promising result in removing manganese from groundwater. Additional tests should be performed on the filters by increasing the volume of groundwater to be filtered and the amount of filter material in the filters.