Repository of Faculty of Chemical Engineering and Technology University of Zagreb
Not a member yet
2768 research outputs found
Sort by
Isolation and selection of yeasts for bioethanol production from acid hydrolyzate of brewer's spent grain
No full textBioetanol je alkohol proizveden mikrobnom fermentacijom. U svrhu proizvodnje etanola najviše se koriste šećerna trska, repa i kukuruz, ali se sve više kao zamjenski supstrat spominje lignoceluloza, jeftin, obnovljivi izvor energije, kojeg u prirodi ima u velikim količinama. Proces proizvodnje etanola fermentacijom najčešće se provodi korištenjem kvasaca Saccharomyces cerevisiae. U procesu proizvodnje etanola iz lignocelulozne sirovine, nedostatak korištenja S. cerevisiae je nemogućnost rasta na pentozama, laktozi i polisaharidima zbog toga što njegov metabolizam ne stvara odgovarajuće enzime, a pentofosfatni put ne radi učinkovito. Zbog toga se sve više istražuju mikroorganizmi s mogućnošću fermentacije tih spojeva (kvasci Schizosaccharomyces pombe, Kluyveromyces lactis, rodovi Candida i Pichia). Cilj ovog rada bio je izolirati kvasce koje mogu učinkovito proizvesti bioetanol iz heksoza i pentoza. U tu svrhu, izolirani su i identificirani kvasci Kluyveromyces marxianus i Candida krusei. Tijekom preliminarnih istraživanja ispitana je učinkovitost procesa fermentacije glukoze kvascem S. cerevisiae u membranskom reaktoru pri čemu je učinkovitost procesa iznosila E = 18,015±5,370% što je znatno manje u usporedbi sa šaržnim procesom pri istim početnim koncentracijama kvasca i šećera, gdje je učinkovitost procesa iznosila E = 80,668±0,561%. U sljedećem koraku ispitan je utjecaj početne koncentracije šećera glukoze (5, 10 i 50 g/L) i ksiloze (5, 10 i 20 g/L) na proizvodnju bioetanola korištenjem kvasca K. marxianus i C. krusei. Prilikom fermentacije glukoze kvascem K. marxianus najveći koeficijent konverzije supstrata u produkt
(YP/S = 0,093±0,006 g/g), učinkovitost procesa
(E = 18,194±1,278 %) i produktivnost procesa (Pr = 0,141±0,009 g/(L·h)) postignuti su prilikom fermentacije glukoze čija je početna koncentracija iznosila 5 g/L. Prilikom fermentacije glukoze kvascem C. krusei, najveći koeficijent konverzije
(YP/S = 0,105±0,009 g/g) i učinkovitost procesa (E = 20,559±1,702 %) postignuti su prilikom fermentacije 5 g/L glukoze dok je najveća produktivnost procesa (Pr = 0,038±0,002 g/(L·h)) postignuta fermentacijom 10 g/L glukoze. Analizom dobivenih produkata na kraju procesa fermentacije ustanovljeno je da niti jedan kvasac nije učinkovit u proizvodnji bioetanola iz ksiloze, ali oba kvasca proizvode druge vrijedne sirovine poput 2,3-butandiola. Najveće koncentracije 2,3-butandiola, γBT = 0,412±0,018 g/L za kvasac K. marxianus i
γBT = 1,860±0,044 g/L za C. krusei, dobivene su fermentacijom podloga koje su sadržale
10 g/L, odnosno 20 g/L ksiloze. S obzirom na dobivene rezultate, na kraju istraživanja provedena je dvostupanjska fermentacija na kiselinskom hidrolizatu pivskog tropa. U prvom stupnju je provedena fermentacija heksoza pomoću kvasca S. cerevisiae, a u drugom fermentacija pentoza pomoću kvasaca K. marxianus i C. krusei pri čemu su dobiveni sljedeći pokazatelji uspješnosti za K. marxianus YP/S = 6,024±0,326 g/g, YP/S = 0,451±0,024 g/g,
E = 88,350±4,776 %, Pr = 0,262±0,014 g/(L·h) i γBT = 1,710±0,043 g/L te za C. krusei
YP/S = 5,632±0,193 g/g, YP/S = 0,421±0,014 g/g, E = 82,589±2,830 %,
Pr = 0,245±0,008 g/(L·h) i γBT = 1,019±0,022 g/L.Bioethanol is an alcohol produced by microbial fermentation. Normally, sugarcane, beets and corn are the main crops used for ethanol production. However, there is a growing interest in using lignocellulose, an abundant and inexpensive renewable energy source, as a potential replacement substrate. The yeast Saccharomyces cerevisiae is typically used in the fermentation process for ethanol production. However, in ethanol production from lignocellulosic materials, S. cerevisiae encounters limitations in metabolizing pentoses, lactose, and polysaccharides due to the lack of suitable enzymes and inefficient functioning of the pentose phosphate pathway. Therefore, research efforts are increasingly focused on microorganisms capable of fermenting these compounds, such as the yeasts Schizosaccharomyces pombe, Kluyveromyces lactis, and Candida and Pichia genera. The aim of this study was to isolate yeasts capable of efficiently producing bioethanol from hexoses and pentoses. For this purpose, the yeasts Kluyveromyces marxianus and Candida krusei were isolated and identified. In preliminary studies, the efficiency of glucose fermentation by S. cerevisiae yeast in a membrane reactor was investigated. The result was a process efficiency of E = 18.015±5.370%, which is significantly lower than batch processes with the same initial yeast and sugar concentrations, where the efficiency was 80.668±0.561%. Next, the influence of initial glucose (5, 10, and 50 g/L) and xylose sugar
(5, 10, and 20 g/L) concentrations on bioethanol production with K. marxianus and C. krusei yeasts was investigated. Fermentation of glucose with yeast K. marxianus achieved the highest substrate-to-product conversion coefficient (YP/S = 0.093±0.006 g/g), process efficiency (E = 18.194±1.278%), and process productivity (Pr = 0.141±0.009 g/(L·h)) when the initial glucose concentration was 5 g/L. In glucose fermentation with C. krusei yeast, the highest conversion coefficient (YP/S = 0.105±0.009 g/g) and process efficiency
(E = 20.559±1.702%) were obtained with 5 g/L glucose, while the highest process productivity (Pr = 0.038±0.002 g/(L·h)) was achieved with 10 g/L glucose. Analysis of the final fermentation products revealed that none of the yeasts was efficient in producing bioethanol from xylose, but both yeasts produced other valuable compounds such as
2,3-butanediol. The highest concentrations of 2,3-butanediol, γBT = 0.412±0.018 g/L for K. marxianus yeast and γBT = 1.860±0.044 g/L for C. krusei, were obtained during fermentation with a substrate containing 10 g/L and 20 g/L xylose, respectively. Based on the obtained results, two-stage fermentation with acid hydrolysate from brewer's grains was performed at the end of the study. In the first stage, hexose fermentation was performed with the yeast S. cerevisiae, while in the second stage, pentose fermentation was performed with the yeasts K. marxianus and C. krusei. The following performance indicators were obtained for
K. marxianus: YP/S = 6.024±0.326 g/g, YP/S = 0.451±0.024 g/g, E = 88.350±4.776%,
Pr = 0.262±0.014 g/(L·h), and γBT = 1.710±0.043 g/L, and for C. krusei:
YP/S = 5.632±0.193 g/g, YP/S = 0.421±0.014 g/g, E = 82.589±2.830%,
Pr = 0.245±0.008 g/(L·h), and γBT = 1.019±0.022 g/L
Preparation of biocatalysts
No full textBiokatalizatori, enzimi, se koriste za ubrzavanje biokemijskih reakcija u živim organizmima. Upotrebljavaju se u velikom rasponu industrija, poput farmaceutske, agrokemijske, prehrambene te u raznim znanstvenim granama. Zahvaljujući toj industrijskoj važnosti biokatalizatora razvijene su razne metode njihove pripreme. Mikrobna fermentacija, kultura biljnih i životinjskih stanica, uz DNK rekombinantnu tehnologiju omogućuju olakšanu sintezu specifičnih enzima. Krajnji produkt, biokatalizator, dobiva se tek nakon pročišćavanja koje uključuje izolaciju enzima iz žive stanice i daljnje postupke poput centrifugiranja i isoljavanja. Tako izolirani enzim podvrgava se metodama poput gel elektroforeze i kromatografije kako bi se uklonili svi neželjeni produkti.Biocatalysts, enzymes, are used to accelerate biochemical reactions in living organisms. They are used in a wide range of industries, such as pharmaceutical, agrochemical, food and in various scientific branches. Thanks to this industrial importance of biocatalysts, various methods of their preparation have been developed. Microbial fermentation, the culture of plant and animal cells, along with DNA recombinant technology enable an easier synthesis of specific enzymes. The final product, the biocatalyst, is obtained after purification, which includes the isolation of the enzyme from the living cell and further procedures such as centrifugation and salting out. The isolated enzyme is then subjected to methods such as gel electrophoresis and chromatography in order to remove all unwanted products
Investigation of the influence of organic solvents on the activity of halohydrin dehalogenase in the ring-opening reaction of para-nitrostyrene oxide
No full textOrganska otapala se zbog svoje prirode i kompatibilnosti s nepolarnim organskim spojevima koriste u većini sintetskih reakcija u industrijskom mjerilu. Takvi kemijski procesi često zahtijevaju reakcije u više stupnjeva i kontaminirajuće kemijske reagense. Biotehnološka alternativa takvim kemijskim procesima uključuje enzime koji djeluju kao biokatalizatori, omogućuju korištenje sirovina na biološkoj osnovi te smanjuju broj koraka reakcije, što može biti popraćeno jeftinijom proizvodnjom. Kao rezultat ovog pristupa, dobivaju se produkti visoke kvalitete na ekonomski i tehnološki konkurentan i održiv način. Iako se biokatalitički procesi smatraju idealnim rješenjem za razvoj održivih proizvodnih sustava i unatoč ogromnom napretku u otkrivanju i razvoju enzima u području molekularne biologije, često postignuta niska produktivnost biokatalitičkog procesa, zajedno s niskom stabilnošću i aktivnosti enzima, sprječava da se njihov potencijal ostvari u industrijskim procesima. Halogenhidrin-dehalogenaze (HHDH) su vrlo rijetki enzimi koji prirodno sudjeluju u bakterijskoj razgradnji halogenih spojeva, a zbog njihovog katalitičkog potencijala pripadaju u skupinu industrijski relevantnih biokatalizatora. U radu je korišten C-tip enzima iz skupine halogenhidrin-dehalogenaza (HheC) izoliran iz genetski modificirane bakterije Escherichia coli. Ispitana je aktivnost HheC enzima, u prisutnosti dvanaest različitih organskih otapala, testom pomoću para-nitrostiren oksida (PNSO) s bromidnim ionima u reakciji otvaranja prstena uz nastajanje para-nitro-2-brom-1-feniletanola (PNSHH). Aktivnost enzima određena je metodom početnih reakcijskih brzina, a koncentracije PNSHH i PNSO određene su pomoću pripremljenih baždarnih pravaca. Pripremljeni uzorci su analizirani pomoću HPLC uređaja, a utjecaj volumnih udjela organskih otapala na specifičnu aktivnost enzima prikazan je grafički. Dobivene vrijednosti logP i c50 organskih otapala prikazane su tablično. Zbog toksičnosti ili zapaljivosti mnogih organskih otapala, sve više se koriste „zelene“ alternative u pogledu „zelenih“ organskih otapala. U radu su ispitana četiri „zelena“ organska otapala koja se dobivaju iz prirodnih izvora.Due to their nature and compatibility with non-polar organic compounds, organic solvents are used in most synthetic reactions on an industrial scale. Such chemical processes often require multistep reactions and contaminating chemical reagents. A biotechnological alternative to such chemical processes includes enzymes that act as biocatalysts, enable the use of biologically based raw materials and reduce the number of reaction steps which can be accompanied by cheaper production. As a result, high quality products are obtained in an economically and technologically competitive and sustainable manner. Although biocatalytic processes are considered as an ideal solution for the development of sustainable production systems and despite tremendous advances in the discovery and development of enzymes in the field of molecular biology, the often achieved low productivity of the biocatalytic process together with the low stability and activity of enzymes, prevents their potential from being realized in industrial applications processes. Halohydrin dehalogenases (HHDH) are very rare enzymes that naturally participate in the bacterial degradation of halogenated compounds and due to their catalytic potential they belong to industrially relevant biocatalysts. This work uses a C-type enzyme from the halohydrin dehalogenase group (HheC) isolated from a genetically modified bacterium Escherichia coli. The activity of the HheC enzyme, in the presence of twelve different organic solvents, was tested using para-nitrostyrene oxide (PNSO) with bromide ions in the ring-opening reaction with the formation of para-nitro-2-bromo-1-phenylethanol (PNSHH). Enzyme activity was determined using the initial reaction rates method and the concentrations of PNSHH and PNSO were determined using a prepared calibration curves. The prepared samples were analyzed using an HPLC device and the influence of volume ratios of organic solvents on the specific activity of the enzyme was shown graphically. The obtained values of logP and c50 of organic solvents are presented in a table. Due to the toxicity or flammability of many organic solvents, there are green alternatives in terms of green organic solvents that are increasingly being used.
Four green organic solvents obtained from natural sources were tested in this paper
Effect of microplastic on removal of pesticides with membrane separation processes
No full textNova zagađivala (engl. emerging contaminants) predstavljaju jednu od najvećih opasnosti za okoliš. Pod nova zagađivala ubrajaju se prirodne ili sintetičke kemikalije ili mikroorganizmi koji se obično ne nadziru u okolišu. To su farmaceutici, pesticidi, industrijske kemikalije, površinski aktivne tvari, proizvodi za osobnu njegu. Membranski separacijski procesi pokazali su se učinkoviti pri uklanjanju pesticida iz otpadnih i drugih voda. Uklanjanje novih zagađivala iz vode i okoliša postalo je prioritetno istraživanje posljednjih desetljeća. U ovom radu ispitivan je utjecaj mikroplastike na uklanjanje pesticida membranskim separacijskim procesima. Ispitivani su metiokarb i imidakloprid, insekticidi koji dugo ostaju u metaboličkim procesima u biljci i koji su zakonom zabranjeni u Republici Hrvatskoj. Ultrafiltracija, nanofiltracija i reverzna osmoza, su membranski separacijski procesi koji su bili korišteni u ispitivanju učinkovitosti uklanjanja pesticida pri radnom tlaku od 10 bar. Koristilo se 5 membrana, GH, GK, NF90, XLE i NF. Učinkovitost uklanjanja pesticida ovisi o veličini pora membrane pa se pesticidi različito zadržavaju na membranama. Ultrafiltracijom nije moguće ukloniti pesticide iz otopina s ili bez mikroplastike, faktori zadržavanja nanofiltracijskih membrana bili su > 60 %, dok se revezno osmotskim membranama najviše pesticida može ukloniti, do 90 %. Došlo je do manjih interakcija između korištenih ultrafiltracijskih membrana, odnosno membrana s većim porama. Prisutnost mikroplastike nije značajno promijenilo učinkovitost zadržavanja pesticida s korištenim membranama.Emerging contaminants pose one of the greatest treats to the environment. Emerging contaminants include natural or synthetic chemicals or microorganisms that are not usually monitored in the environment. These include pharmaceuticals, pesticides, industrial chemicals, surfactants, and personal care products. Membrane separation processes have proven effective in removing pesticides from wastewater and other water bodies. Removal of these emerging contaminants from water and the environment has become a priority research objective in recent years. In this work, the influence of microplastics on the removal of pesticides with membrane separation processes was investigated. The tested pesticides methiocarb and imidacloprid are insecticides that remain in the metabolism of plants for a long time and are prohibited by law in the Republic of Croatia. Ultrafiltration, nanofiltration, and reverse osmosis are membrane separation processes that were used in testing the effectiveness of pesticide removal at a working pressure of 10 bar. Five membranes were used: GH, GK, NF90, XLE, and NF. The efficiency of pesticide removal depends on the size of membrane pores, so pesticides are retained differently on membranes. Ultrafiltration cannot remove pesticides from solutions with, or without microplastics. The retention factors of nanofiltration membranes were > 60%, while most pesticides can be removed with reverse osmotic membranes, up to 90%. There were interactions between the ultrafiltration membranes used, i.e., membranes with larger pores. The presence of microplastics did not significantly affect the pesticide retention efficiency with the membranes used
Broom fibers as reinforcing materials for polypropylene-based composites
No full textU današnje vrijeme, proizvodnja prirodnih kompozitnih materijala u velikom je usponu, a njihova primjena zastupljena je u raznim industrijama. U prvom dijelu ovog rada navedene su osnovne informacije i povijesni pregled o polimerima i polimernim materijalima, o kompozitima, kao i o kompozitima polipropilena i vlaknima brnistre čija su svojstva u ovom radu ispitivana. Drugi dio rada obuhvaća eksperimentalni dio, pripremu kompozita ojačanih vlaknima brnistre, analizu tako pripremljenih kompozita diferencijalnom pretražnom kalorimetrijom, termogravimetrijskom analizom, i stupanj bubrenja. Dobiveni rezultati uspoređuju se sa svojstvima čistog polipropilena te se donose zaključci o utjecaju vlakana brnistre na svojstva kompozita na osnovi polipropilena.Nowadays, the production of natural composite materials is on the rise. Also, their application is becoming more common every day in different industries due to the profitability of their production, but also crucially, due to the better modified properties that can be achieved in combination with plant fibers. In the first part of this paper, basic information and a historical overview about polymers and polymer materials, about composites, as well as polypropylene and Spanish broom, whose properties were examined in this paper, are given. The second part of this paper includes the experimental part, the preparation of composites reinforced with broom fibers, the analysis of the composites prepared in this way by differential search calorimetry, thermogravimetric analysis, but also the examination of their behavior in contact with water. The obtained results are compared with the properties of pure polypropylene, and conclusions are drawn about the influence of broom fibers on the properties of polypropylenebased composites
Quantitative energy dispersive X-ray spectrometry
No full textEnergijski razlučujuća rendgenska spektrometrija analitička je tehnika koja omogućuje identifikaciju kemijskih elemenata u uzorku pomoću pretražnog elektronskog mikroskopa. Ova tehnika detektira rendgenske zrake uzorka pobuđene snopom elektrona pretražnog elektronskog mikroskopa. Temelji se na spoznaji da je energija rendgenskih zraka povezana s atomskim brojem atoma, a njihov intenzitet s masenim udjelom atoma u uzorku. U ovom su radu uzorci poznatog i nepoznatog sastava karakterizirani pomoću pretražnog elektronskog mikroskopa te je na njima provedena energijski razlučujuća rendgenska spektrometrija. Dobiveni podaci prikazani su grafički, te su analizirani karakteristični maksimumi za pojedine elemente. Uspoređeni su rezultati računalne analize dobivene softverskom analizom podataka s grafičkom identifikacijom linija. Izračunati su množinski udjeli elemenata u spojevima uzoraka prema rezultatima računalne analize. Izvedena je korelacija između masenog sastava uzorka i odaziva dobivenog EDS analizom tako da su određeni
Cliff-Lorimerovi faktori za pojedine elemente koji čine uzorke. Konačno, dan je zaključak o prednostima i nedostatcima te analitičke tehnike.Energy dispersive X-ray spectrometry is an analytical technique that enables the identification of chemical elements in a sample using a scanning electron microscope.
This technique detects X-rays from the sample during bombardment by an electron beam. Detected X-rays are related to the atomic number of atoms and their intensity to the mass fraction of atoms in the sample. In this work, samples of known and unknown composition were characterised using a scanning electron microscope and energy-dispersive X-ray spectrometry was performed on them. The obtained data are presented graphically, and the characteristic lines for individual elements are analyzed. The results of computer analysis obtained by software data analysis with graphic identification of peaks were compared.
The mass fractions of the elements in the sample compounds were calculated according to the data obtained by the software analysis. The correlation between the mass composition of the sample and the response obtained by EDS analysis was performed, so that the
Cliff-Lorimer factors were determined for the individual elements that make up the samples. Finally, a conclusion is given on the advantages and disadvantages of this analytical technique
Natural pigments as wearable chemical sensors on skin
No full textRazvoj tehnologije i broj objavljenih radova na temu bežičnih i nosivih (engl. wearable) optičkih kemijskih senzora je u konstantnom porastu od 2011. godine. Njihov jednostavan način rada, cjenovna pristupačnost i mogućnost komercijalizacije ih čini zanimljivim ne samo znanstvenicima, već i ekonomistima velikih korporacija. Nosivi senzori koriste se danas rutinski za praćenje zdravstvenog stanja pacijenata i kondicije profesionalnih i rekreativnih sportaša. U tu svrhu najčešće se primjenjuju u obliku pametnih satova koji pomoću minijaturiziranog optoelektroničkog sučelja metodom fotopletizmografije (engl. photoplethysmography, PPG), mogu mjeriti broj otkucaja srca, zasićenost krvi kisikom te procjenjivati niz drugih parametara i digitalnih biomarkera. U novije vrijeme znanstvena istraživanja usmjerena su prema razvoju nosivih kemijskih senzora, koji bi bili u stanju dati informacije o (bio)kemijskom sastavu dostupnih biofluida (npr. znoj, međustanična tekućina, suze, slina). Kontinuirano praćenje koncentracije (bio)kemijskih parametara u kombinaciji s fizičkim indikatorima predstavlja inovativni multimodalni pristup dijagnostici i terapiji, čiji izuzetan uspon je vidljiv u znanstvenoj i patentnoj literaturi posljednjih godina. Cilj ovog rada bio je ispitati primjenjivost komercijalno dostupnog PPG optičkog senzorskog sustava (model MAX30101) za mjerenje odabranog kemijskog parametra (pH vrijednost) koristeći prirodni pigment kurkumin kao pH indikator. Kurkumin je prirodni pigment dobiven iz podzemne stabljike biljke Curcuma longa, te je kao takav privlačan jer predstavlja ekološki prihvatljivu alternativu umjetnim, i često štetnim pigmentima. Stoga je njegova potencijalna primjena u nosivim senzorima, u direktnom kontaktu s kožom/znojem, u potpunosti moguća. Osim toga, kurkumin je meta istraživanja i u medicini jer su dokazana njegova antikancerogena svojstva, što podcrtava njegovu biokompatibilnost. Neutralne i kisele otopine s kojima je kurkumin u kontaktu bojaju ga jarko žuto, a s porastom pH vrijednosti on mijenja boju u crveno-narančasto-smeđu. Imobilizacija kurkumina izvedena je na papiru, metodom isparavanja otapala. Papir je vrlo zahvalna podloga za nosive kemijske senzore jer je dostupan u različitim strukturnim izvedbama i svojstvima. Imobilizacijom tri otopine kurkumina različitih koncentracija dobiveni su jednokratni testni papirići koji su spektroskopski karakterizirani pri različitim vrijednostima otopina pH pufera u rasponu od 8 do 13. Mjerenja izvedena primjenom fotopletizmografskog (PPG) senzora uspoređena su s mjerenjima standardnog laboratorijskog instrumenta za mjerenje reflektancije. Zaključeno je da odabrani PPG senzorski sustav primijenjen na prikazani način može razlikovati pH vrijednosti s određenom točnošću. Eksperimentalno su izračunate pKa1 vrijednosti kurkumina kao imobiliziranog indikatora na papiru dobivene u dva seta mjerenja PPG senzorom MAX30101 te iznose
pKa = 8,91 i pKa = 9,16. Ista veličina određena standardnim instrumentom za mjerenje reflektancije spektrometrom OceanOptics mjerenjima istih uzoraka papirnih senzora iznosi pKa = 9,43.The development of technology and the number of published papers on wearable optical chemical sensors is in a constant rise since 2011. Their simple way of work, financial accessibility and possibility of commercialisation makes them interesting not only to scientists, but to economists of big corporations too. Wearable sensors today are rutinely used to track medical states of patients and physical conditions of professional and amateur athletes alike. For that purpose, they are most often used in the form of smart watches that, using a miniaturised optoelectronic interface and the method of photophletysmography (PPG), can measure heart rate, blood oxygen saturation, and evaluate a number of other parameters and digital biomarkers. Recently, scientific research has been directed towards the development of wearable chemical sensors, which would be able to provide information about the (bio)chemical composition of available biofluids (eg. sweat, intercellular fluid, tears, saliva). Continuous monitoring of the concentration of (bio)chemical parameters in combination with physical indicators represents an innovative multimodal approach to diagnostics and therapy, the remarkable rise of which is visible in the scientific and patent literature in recent years. The aim of this work was to examine the applicability of a commercially available PPG optical sensor system (model MAX30101) for measuring a selected chemical parameter (pH value) using the natural pigment curcumin as a pH indicator. Curcumin is a natural pigment obtained from the underground stem of the plant Curcuma longa, and as such is attractive because it represents an environmentally friendly alternative to artificial, and often harmful, pigments. Therefore, it's potential application in wearable sensors, in direct contact with skin/sweat, is entirely possible. In addition, curcumin is the target of research in medicine as its anticancer properties have been proven, which underlines its biocompatibility. Neutral and acidic solutions with which curcumin is in contact color it bright yellow, and as the pH value increases, it changes color to red-orange-brown. Immobilization of curcumin was performed on paper, using the solvent evaporation method. Paper is a very useful substrate for wearable chemical sensors because it is available in different structural designs and properties. By immobilizing three curcumin solutions of different concentrations, disposable test papers were obtained, which were spectroscopically characterized at different values of pH buffer solutions ranging from 8 to 13. Measurements performed using a photoplethysmographic (PPG) sensor were compared with measurements of a standard laboratory instrument for measuring reflectance. It was concluded that the selected PPG sensor system applied in the manner shown can distinguish pH values with a certain accuracy given that pKa1 values which were determined using the PPG sensor
(pKa = 8,91 and pKa = 9,16) do not differ considerably from the one that was determined using the standard instrument OceanOptics (pKa = 9,43)
Modifications of silicate filler with silanes
No full textU ovom radu proučavano je silikatno punilo modificirano silanima (3-aminopropilsilantriolom, 3-aminopropiltrietoksisilanom, 3-metakriloksipropiltrimetoksisilanom, heksametildisilazanom i 3-glicidoksipropiltrimetoksisilanom) te industrijski obrađeno punilo R 711. Po definiciji, punila su materijali u obliku čestica koji se dodaju polimerima kako bi se poboljšala fizikalna svojstva i/ili smanjila cijena kompozita. Površina prirodnih punila na bazi silicijevog dioksida, SiO2, je djelomično ili potpuno hidratizirana i stoga hidrofilna. Taloženjem organskih tvari na hidrofilnu površinu prirodnih i sintetskih anorganskih punila može se poboljšati njihova disperzibilnost i funkcionalnost. Osnovna metoda za pretvaranje hidrofilnih anorganskih punila u ona koja imaju kovalentno vezane organske skupine na površini je obrada silanom. Organofunkcionalni silani su hibridni materijal silana i u novije vrijeme su privukli veliku pozornost zahvaljujući svojim svestranim svojstvima, koja nude široki raspon primjena. Ekološki su prihvatljivi i ne nalaze se u prirodi; uglavnom se sintetiziraju iz silicijeva dioksida. Koriste se u industriji boja kao promotori prianjanja ili sredstva za umrežavanje koja stvaraju jake veze s gornjim slojevima premaza te kao hidrofobizatori površine. Uzorci su karakterizirani mjerenjima kontaktnoga kuta i površinske energije, diferencijalnom pretražnom kalorimetrijom (DSC) i termogravimetrijskom analizom (TGA) te infracrvenom spektroskopijom s Fourierovom transformacijom (FTIR). Rezultati analize kontaktnoga kuta ukazuju na to da je došlo do hidrofobizacije površine. DSC analizom utvrđene su temperature staklastog prijelaza, a TGA analizom utvrđeno je sniženje toplinske postojanosti kompozita. Rezultati FTIR-a potvrdili su uspješnu modifikaciju površine silicijevog dioksida.In this paper, silicate filler modified with silanes (3-aminopropylsilanetriol, 3-aminopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, hexamethyldisilazane and 3-glycidoxypropyltrimethoxysilane) and industrially processed filler R 711 were studied. By definition, fillers are particulate materials that are added to polymers to improve the physical properties and/or reduce the cost of the composite. The surface of natural fillers based on silicon dioxide, SiO2, is partially or completely hydrated and therefore hydrophilic. By depositing organic substances on the hydrophilic surface of natural and synthetic inorganic fillers, their dispersibility and functionality can be improved. The basic method for converting hydrophilic inorganic fillers into ones with covalently bound organic groups on the surface is silane treatment. Organofunctional silanes are a hybrid material of silanes and have recently attracted a lot of attention for their versatile properties, which offer a wide range of applications. They are ecologically acceptable and are not found in nature; they are mainly synthesized from silica. They are used in the paint industry as adhesion promoters or cross-linking agents that create strong bonds with the upper layers of the coating and as surface hydrophobizers. The samples were characterized by contact angle and surface energy measurements, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The results of the contact angle analysis indicate that the hydrophobization of the surface has occurred. DSC analysis determined the glass transition temperatures, and TGA analysis determined the decrease in thermal stability of the composite. The FTIR results confirmed the successful modification of the silica surface
Inkjet printing of silver nanoparticles on plastic substrates obtained by additive manufacturing
No full textS razvojem 3D-ispisane elektronike, stvara se prostor za nova istraživanja o kombinacijama materijala, tehnikama ispisa i sinteriranjima sustava. Od vodljivih materijala posebno se ističu nanočestice plemenitih metala, pogotovo srebra, na podlogama relativno niske cijene i brze izrade. Plastične podloge dobivene aditivnom proizvodnjom pronalaze primjene u fleksibilnoj i nosivoj elektronici. U ovome radu tri različite nanosrebrne tinte su tintno ispisane na šest različitih plastičnih podloga, od kojih su dvije komercijalne (poliimid i poli(etilen-tereftalat), a četiri 3D-ispisane (poli(etilen-tereftalat) obogaćen glikolom, akrilonitril/butadien/stiren, poli(mliječna kiselina) i poli(vinil-butiral)). Tehnika 3D-ispisa aditivnih podloga bila je proizvodnja rastaljenim filamentom. Dobiveni uzorci sinterirali su se intenzivnom pulsirajućom svjetlošću, s i bez prethodnog sušenja. Uz preliminarna ispitivanja svake kombinacije podloge i tinte, optimirani su uvjeti ispisa i sinteriranja uz pomoć programske podrške Design-Expert. Uzorci su karakterizirani mjerenjem površinskog otpora pomoću sonde u četiri točke.
Najniži površinski otpor pokazivali su uzorci komercijalne nanosrebrne Novacentrix JS-B25HV i amfifilne nanosrebrne tinte na komercijalnoj poliimidnoj podlozi. Jedina 3D-ispisana podloga koja je imala prihvatljive vrijednosti površinskog otpora bila je poli(vinil-butiralna).With the development of 3D-printed electronics, a space for new research in combinations of materials, printing techniques and sintering systems is created. Nanoparticles of precious metals, especially silver, on relatively low-cost and fast-made substrates stand out among the conductive materials. Plastic substrates obtained by additive manufacturing find application in flexible and wearable electronics. In this work, three different nanosilver inks were inkjet printed on six different plastic substrates, two of which are commercial (polyimide and polyethylene terephthalate), and four 3D-printed (polyethylene terephthalate glycol, acrylonitrile/butadiene/styrene, polylactic acid and poly(vinyl butyral)). The additive substrate 3D-printing technique was fused filament fabrication. Samples were sintered by intense pulsed light, with and without pre-drying. With preliminary tests of each substrate and ink combination, conditions for printing and sintering were optimized with the help of
Design-Expert software. The samples were characterized by measuring the surface resistance using a four-point probe. The lowest surface resistance was shown by both commercial nanosilver Novacentrix JS-B25HV and amphiphilic nanosilver ink samples on a commercial polyimide substrate. The only 3D-printed substrate that had measurable surface resistance values was poly(vinyl butyral)
Preparation of conductive and stretchable films based on PEDOT copolymer
No full textOtkriće vodljivosti kod nekih vrsta polimera potaknulo je znanstveni interes i nova istraživanja. Vodljivi polimeri imaju velik potencijal te nude zanimljiva rješenja tehničkih problema. Dobra električna i optička svojstva vodljivih polimera omogućuju njihovu primjenu u elektrokromnim uređajima, solarnim ćelijama, senzorima te nosivoj elektronici. Jedan od najpoznatijih predstavnika vodljivih polimera je poli(3,4-etilendioksitiofen) (PEDOT). Kopolimerizacijom PEDOT-a s nekim drugim polimerima mijenjaju se svojstva produkta.
Cilj ovog rada je razviti vodljive i istezljive filmove na bazi PEDOT kopolimera. U tu svrhu izrađeni su kompozitni filmovi PEDOT-a i termoplastičnog elastomera stiren-etilen-butilen-stirena (SEBS) koji doprinosi istezljivosti polimerne mješavine. Naknadnom polimerizacijom prijenosom atoma (ATRP) na lanac PEDOT-a ugrađen je poli(akrilat-uretan) (PAU) koji bi zbog posjedovanja vodikovih veza mogao ostvariti fizikalno umrežavanje te tako postići svojstvo samozacijeljivanja filmova. Produkti reakcija okarakterizirani su metodama instrumentalne analize: nuklearna magnetska rezonancija (NMR), infracrvena spektroskopija s Fourierovom transformacijom (FTIR), termogravimetrijska analiza (TGA), diferencijalna pretražna kalorimetrija (DSC), metoda dinamičkog raspršenja svjetlosti (DLS), metoda sonde s 4 točke (4PP) te snimanje pretražnim elektronskim mikroskopom (SEM). Izrađeni polimerni filmovi pokazali su kombinaciju električne provodnosti, istezljivosti, stabilnosti i samozacijeljivosti koja im omogućava potencijalnu primjenu u nosivoj elektronici.The discovery of the conductivity of some polymers has aroused scientific interest and spurred new research. Conductive polymers have great potential and offer interesting solutions to technical problems. The good electrical and optical properties of conductive polymers enable their use in electrochromic devices, solar cells, sensors and wearable electronics. One of the best-known representatives of conductive polymers is
poly(3,4-ethylenedioxythiophene) (PEDOT). Copolymerization of PEDOT with some other polymers changes the properties of the product. The aim of this work is to develop conductive and stretchable films based on PEDOT copolymers. For this purpose, composite films were prepared from PEDOT and the thermoplastic elastomer styrene-ethylene-butylene-styrene (SEBS), which contributes to the stretchability of the polymer blend.
By subsequent atom transfer polymerization (ATRP) poly(acrylate-urethane) (PAU) was grafted to PEDOT backbone to achieve physical crosslinking and thus the self-healing properties of the films due to the presence of hydrogen bonds. The reaction products were characterized by instrumental analytical methods: Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Dynamic Light Scattering (DLS), 4-point Probe Method (4PP), and Scanning Electron Microscopy (SEM). The fabricated polymer films showed a combination of electrical conductivity, stretchability, stability, and self-healing, making them potentially applicable in wearable electronics