Síntese e aplicação dos materiais inorgânicos como sensores eletroquímicos

Orientador: Juliano Alves BonacinTese (doutorado) - Universidade Estadual de Campinas, Instituto de QuímicaResumo: Nossa sociedade moderna se encontra em um constante crescimento e desenvolvimento, o que torna inevitável o aumento da demanda por energia, alimento, medicamentos e qualidade de vida. Um ponto em comum entre inúmeras aplicações na área de saúde, bem-estar e inúmeros processos industriais reside na quantificação de espécies moleculares de interesse. Neste sentido, o desenvolvimento de sensores tem se tornado indispensável para o mundo moderno. Dentre os sensores químicos, o subgrupo dos sensores eletroquímicos conquistou espaço nos últimos anos por conta de sua versatilidade, simplicidade em termos de arranjo experimental, além do baixo custo. A eficiência dos sensores depende do potencial de um material ativo que será acoplado a um transdutor. Desta maneira, polímeros de coordenação eletroativos como o azul da Prússia, com suas propriedades estruturais e redox bem conhecidas, têm sido explorados para essa aplicação, com resultados excepcionais. Em sua forma reduzida, o azul da Prússia possui uma interessante atividade catalítica, capaz de reduzir peróxido de hidrogênio com alta velocidade reacional e baixo sobrepotencial. Desta maneira, podem ser vistos como "peroxidases artificiais". Neste projeto, estudamos principalmente o desenvolvimento de sensores eletroquímicos e o azul da Prússia foi usado como camada eletroativa. Também realizamos a modificação de diferentes substratos convencionais, como ouro, platina, carbono vítreo, e eletrodos impressos. Além disso, técnicas modernas de impressão 3D foram utilizadas para a criação de eletrodos 3D de grafeno condutivo, os quais também foram modificados com azul da Prússia. O estudo eletroquímico comparativo entre substratos convencionais e os impressos em 3D modificados com azul da Prússia também foi realizado. Comparamos o azul da Prússia e seu análogo, amino azul da Prússia, para a modificação de eletrodos impressos. Além disso, o comportamento redox do azul da Prússia e a eletro-oxidação do eletrodo de grafeno impresso em 3D foram estudados in situ por espectroeletroquímica Raman. Por fim, apresentamos em detalhes a construção de um fotoreator e sua aplicação em síntese fotoquímicas de nanomateriais como o azul da Prússia e nanopartículas de ouro e exploramos também o controle do grau de redução de óxido de grafenoAbstract: Our society is in a constant state of growth and development and it is inevitable that demands for energy, food, medicine and welfare will increase. A common point in both human health and industrial processes is information related to quantification of the molecules. In this sense, the development of sensors becomes essential in the modern world. The subgroup of chemical sensors - electrochemical sensors through years have earned special place, because of their remarkable detectability, experimental simplicity and low cost. The efficiency of the sensors depends on a potential active material that will be coupled with transducer. Thus, electroactive coordination polymers such as Prussian blue with its well knowns structural and redox properties has been applied for this purpose and shown remarkable results. In its reduced form Prussian blue has strong catalytic activity to reduce hydrogen peroxide at very fast catalytic rate and with a low overpotential, thus is referred as an "artificial peroxidase". During this this project we have been mainly focused on electrochemical sensors and Prussian blue was used as electroactive layer. Modification of different substrates, the traditional ones such as gold, platinum, glassy carbon and screen ¿ printed electrodes was performed. In addition, remarkable 3D printing technologies were used for the creation of 3D conductive graphene electrodes which were also modified with Prussian blue. The comparative electrochemical studies between Prussian blue modified traditional substrates and 3D electrode were conducted. Also, between Prussian blue and its analogue Prussian blue - Ammine using screen printed electrode. Then, redox behaviour of Prussian blue and electro-oxidation of graphene 3D electrode were studied with in situ Raman spectroelectrochemistry. Lastly, the construction of lab-made photoreactor was presented in detail and tested for the synthesis of gold nanoparticles and reduction of graphene ¿ oxideDoutoradoQuimica InorganicaDoutora em Ciências161819/2014-1CNPQCAPE

Fizičkohemijske karakteristike i kvalitet mekih sireva na tržištu beogradskih pijaca

Cheese as food due to its nutritional value takes an important place in human diet. In Republic Serbia cheeses are produced in industrial dairy plants, but a significant portion are produced in small scale plants and in the individual households, as well. AtBelgrade marketscheeses are daily present and produced in the individual household’soriginating from different geographic localities in Serbia. The aim of this article was to determine the physicochemical characteristics of cheeses at Belgrade markets.Following parameters in cheese samples were determined: total solids, fat in total solids, moisture on a free fat basis, pH value, water activity (aw ) and NaCl content.The results showed that all cheesesamples collected ateight Belgrade markets belonged to the group of soft cheeses according to the values of moisture on a free fat basis (>67%). Out of 83 examined samples most number, 40 (48,19%) belonged to the group of full-fat cheeses, 32 (38,55%) to the group of extra-fat, 10 (12,05%) to the group of semi-fat and 1 (1,20%) sample to the group of low-fat cheeses. None of samples belonged to the skimmed cheeses. Sensory characteristics of all cheeses were in accordance to sensory characteristics for that type of cheese.Sir kao namirnica, zbog svoje hranljive vrednosti,zauzima važno mesto u ishrani ljudi. U Republici Srbiji sirevi se proizvode u industrijskim pogonima,ali značajan deo se proizvodi u zanatskim pogonima, kao i u individualnim domaćinstvima. Na tržištu beogradskih pijaca su svakodnevno zastupljeni sirevi, koji se proizvode u individualnim domaćinstvima i potiču iz različitih geografskih lokaliteta u Republici Srbiji.Cilj rada je bio da se ispitaju fizičkohemijske karakteristike sireva na tržištu beogradskih pijaca.U uzorcima sireva su ispitani sledeći parametri: suva materija, mast u suvoj materiji, voda u bezmasnoj materiji, pH vrednost, aktivnost vode (aw) i sadržaj NaCl. Rezultati su pokazali da su svi ispitani uzorci sireva sa osam beogradskih pijaca pripadali grupi mekih sireva na osnovu sadržaja vode u bezmasnoj materiji(>67%). Od 83 ispitana uzorka najveći broj uzoraka sireva 40 (48,19%) je pripadao grupi punomasnih sireva, 32 (38,55%) grupi ekstramasnih,10 (12,05%) grupi polumasnih i 1 (1,20%) uzorak grupi niskomasnih sireva. Nijedan uzorak sira nije pripadao grupi obranih sireva. U pogledu senzornih karakteristika svi sirevi su odgovarali senzornim karakteristikama za tu vrstu sira

Proizvodnja i karakteristike “Banatskog Sira”

Autohtonous cheeses are products produced in a specific geographical areas as a result of development of tarditional production for many years. „Banatski cheese“ has been producing in Vojvodina, in the Middle Banat in a tarditional mannerat farms (salaš) and inividual households,as well.The aim of this article was to describe the production of "Banastskog cheese, which is produced in tardicionalan manner at househols of Hungarian nationality in the area of Zrenjanin. The cheese samples were examined for the presence of L. monocytogenes, coagulase-positive staphylococci, the number of lactic acid bacteria, Enterobacteriaceae, and physicochemical parameters (total, fat in total solids, fat in total solids, weight of moisture in cheese, moisture on a free fat basis, acidity, pH value,NaCl content. The observation of autohtonous technology was carried out by the survey consisting of questions, which combined the basic elements and technological operations of an autohtonous production.Lactic acid bacteria were the dominant microbiota.The mean value for the number of Lactococcus spp. was 7.45 log CFU / g andLactobacillus spp. 7.20 log cfu/g.In the examined samples were not detected L. monocytogenes and coagulase-positive staphylococci, while the number of Enterobacteriaceae ranged from130 to 2500 cfu/g. The value of total solids in cheese ranged from 67,90 to 73,71% for fat in total solids from 16,96 to 27,98%,for moisture on a free fat basis from 30,84 to 39,63%, total proteins ranged from 23, 92 to 35.95%, the acidity from 15 to 20.75 ° SH, pH value from 4.24 to 5.37 and NaCl content from 4.45 to 13.95%.Autohtoni sirevi su proizvodi nastali u određenom podneblju kao rezultat dugogodišnjeg razvoja tradicionalne proizvodnje. U Vojvodini, u Srednjem Banatu se na tradicionalan način proizvodi “Banatski sir” na salašima i u individualnim domaćinstvima. Cilj ovog rada je bio da se opiše proizvodnja “Banastskog sira“, koji se proizvodi na tardicionalan način u domaćinstvima mađarske nacionalnosti u okolini Zrenjanina. Sirevi su ispitani na prisustvo L. monocytogenes, koagulaza pozitivnih stafilokoka, određivan je broj bakterija mlečne kiseline,enterobakterija, kao ifizičkohemijski parametri (suva materija, mast, mast u suvoj materiji, voda, voda u bezmasnoj materiji, kiselost, pH vrednost i sadržaj NaCl). Snimanje autohtone tehnologije je izvedeno pomoću ankete sastavljene od pitanja, koja objedinjuju osnovne elemente i tehnološke postupke autohtone proizvodnje.Dominantnu mikrofloru su činile bakterije mlečne kiseline. Srednja vrednost broja Lactococcus spp.je bila 7,45 log cfu/g i Lactobacillus spp. 7,20 log cfu/g. U ispitanim uzorcima nisu dokazane L. monocytogenes i koagulaza pozitivne stafilokoke, dok je broj Enterobacteriaceaebio od 130 do 2500 cfu/g. Vrednost za suvu materiju sira se kretala 67,90 do 73,71%, za mast u suvoj materiji sira 16,96 do 27,98%, za vodu u bezmasnoj materiji 30,84 do 39,63%, za ukupne proteine 23,92 do 35,95%, za kiselost 15 do 20,75°SH, pH 4,24 do 5,37 i za sadržaj NaCl 4,45 do 13,95 %

The Insulin-Like Growth Factor System in the Long-Lived Naked Mole-Rat.

Naked mole-rats (Heterocephalus glaber) (NMRs) are the longest living rodents known. They show negligible senescence, and are resistant to cancers and certain damaging effects associated with aging. The insulin-like growth factors (IGFs) have pluripotent actions, influencing growth processes in virtually every system of the body. They are established contributors to the aging process, confirmed by the demonstration that decreased IGF signaling results in life-extending effects in a variety of species. The IGFs are likewise involved in progression of cancers by mediating survival signals in malignant cells. This report presents a full characterization of the IGF system in the NMR: ligands, receptors, IGF binding proteins (IGFBPs), and IGFBP proteases. A particular emphasis was placed on the IGFBP protease, pregnancy-associated plasma protein-A (PAPP-A), shown to be an important lifespan modulator in mice. Comparisons of IGF-related genes in the NMR with human and murine sequences indicated no major differences in essential parts of the IGF system, including PAPP-A. The protease was shown to possess an intact active site despite the report of a contradictory genome sequence. Furthermore, PAPP-A was expressed and translated in NMRs cells and retained IGF-dependent proteolytic activity towards IGFBP-4 and IGF-independent activity towards IGFBP-5. However, experimental data suggest differential regulatory mechanisms for PAPP-A expression in NMRs than those described in humans and mice. This overall description of the IGF system in the NMR represents an initial step towards elucidating the complex molecular mechanisms underlying longevity, and how these animals have evolved to ensure a delayed and healthy aging process

Molecular characterization of Cronobacter sakazakii isolated from different herbal teas and mixtures in Serbia

Cronobacter sakazakii je uzročnik humanih infekcija koje mogu prouzrokovati ozbiljne i čak fatalne posledice kod odojčadi i imunokompromitovanih odraslih osoba i dece. Zbog visoke tolerancije na osmotski stres, C. sakazakii je često izolovan iz dehidratisanih proizvoda, kao što su formule za bebe u prahu i biljni čajevi. Cilj ovih istraživanja je detekcija, identifikacija i molekularna karakterizacija Cronobacter sakazakii izolata iz formula za bebe i različitih biljnih čajeva uzorkovanih u prodavnicama u Srbiji ili testiranih pri kontroli izvoza. U svih 360 analiziranih uzoraka mleka u prahu za bebe nije detektovana kontaminacija bkterijom C. sakazakii. Medjutim, u 192 od 520 testiranih uzoraka čajeva utvrdjeno je prisustvo C. Sakazakii (37.1%). Visoka zastupljenost je detektovana u čajevima za decu - 51.6% i u “bebi” čajevima - 44.1%, a zatim u čajevima za medicinsku upotrebu -38%. Najveća grupa čajeva koji sadrže 1 biljnu vrstu (221) sadržala je 72 C. sakazakii - pozitivnih uzoraka (32.6%) i uključivala je čajeve od Sennae folium, Althaeae radix, Menthae piperitae folium, Chamomilae flos i Urticae folium. Molekularna karakterizacija izolovanih C. sakazakii iz različitih biljnih čajeva rep-PCR, RAPD i 16S rRNA analizom sekvenci ukazala je na visok stepen sličnosti soju C. sakazakii NCTC 8155. S obzirom da je ovo jedan od najpatogenijih kliničkih sojeva, ovi rezultati ukazuju na potrebu za povećanom kontrolom zbog mogućeg rizika koju ove namirnice predstavljaju za imunokompromitovane i zdrave korisnike, a posebno za bebe i decu.Cronobacter sakazakii is an important cause of human infections that can be serious and even fatal among premature neonates and immunocompromised adults or infants. Because of its high tolerance to osmotic stress, C. sakazakii is frequently isolated from dried foods, such as powdered infant formula and herbal teas. The aim of investigation was detection, identification and molecular characterization of Cronobacter sakazakii isolates from infant formula and various herbal teas collected from Serbian market and tested for import control. C. sakazakii was not detected in any of the 360 analysed samples of powdered infant formula. However, 192 out of 520 samples of herbal teas tested were positive for C. sakazakii (37.1%). The high prevalence was observed in teas for children (51.6%) and in “baby” teas (44.1%), followed by medicinal teas (38%). The largest one-herb-teas group (221 samples) contained 72 C. sakazakii-positive samples (32.6%) and involved Sennae folium, Althaeae radix, Menthae piperitae folium, Chamomilae flos and Urticae folium teas. Molecular characterization of isolated C. sakazakii from different herbal teas by rep-PCR, RAPD and 16S rRNA sequences analysis showed the high similarity to C. sakazakii NCTC 8155. Knowing this strain as one of the most pathogenic clinical strains, our results raise concern about the safety risks these foods pose to immunocompromised and healthy consumers, especially for babies and children

Multilocus sequence typing for investigation of diversity of Campylobacter jejuni strains from humans and environment in Norway

This report describes the use of the Multilocus Sequence Typing (MLST) method for typing 32 strains previously identified as Campylobacter jejuni . This system identified a great diversity between the investigated strains. The majority of strains belonged to already existing alleles found on the Campylobacter MLST home page, and most of them represented clonal complexes ST-21 and ST-45, but there were some newly identified alleles as well

Spectroscopic and electrochemical behavior of a supramolecular tetrapyridylporphyrin encompassing four terpyridine(oxalate)chloridoruthenium(II) complexes and its use in nitrite sensors

Supramolecular species combining ruthenium(II) polypyridines and tetrapyridylporphyrins (TPyP) have been employed in electrochemical and molecular sensing devices, because of their unique synergistic properties. In this work, a new tetraruthenated porphyrin, 4-TRoxPyP has been synthesised, encompassing four pyridine bridged [Ru(Cl-tpy)(ox)] complexes (Cl-tpy = chloroterpyridine, ox = oxalate ion). Such species exhibit characteristic electronic transitions of porphyrin and ruthenium polypyridine complexes, such as a Soret band at 414 nm, Q bands at 514 nm, 557 nm and 588 nm and a ruthenium-to-terpy charge-transfer band at 643 nm. A typical tetraruthenated porphyrin redox process has been observed at 0.72 V versus NHE, associated with the peripheral Ru3+/2+ complexes. Their thin films have been prepared by drop casting onto a glassy carbon electrode, and successfully employed in nitrite analysis, by monitoring the chronoamperometric response at the Ru3+/2+ redox gate. A linear relationship between the anodic peak current and concentration of the analyte has been observed from 0 to 0.10 mmol L−1, with a nitrite detection limit of 7.60 μmol L−1437127132CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP#459923/2014-5#02/07066-

ASSEMBLY OF LOW-COST LAB-MADE PHOTOREACTOR FOR PREPARATION OF NANOMATERIALS

In this paper, a low-cost and versatile lab-made photoreactor was constructed for the preparation of nanomaterials such as gold nanoparticles and reduced graphene oxide. The power of the lab-made photoreactor can be easily adjusted according to the number of lamps turned on. Moreover, the lab-made photoreactor allows the utilization of different sources of irradiation with distinct wavelengths. Performance tests for production of gold nanoparticles showed reproducibility and equal efficiency as compared to the literature. Also, the photoreactor powered with UV-A and UV-C as sources of irradiation can be used for modulation of the reduction degree of graphene oxide

ASSEMBLY OF LOW-COST LAB-MADE PHOTOREACTOR FOR PREPARATION OF NANOMATERIALS

<div><p>In this paper, a low-cost and versatile lab-made photoreactor was constructed for the preparation of nanomaterials such as gold nanoparticles and reduced graphene oxide. The power of the lab-made photoreactor can be easily adjusted according to the number of lamps turned on. Moreover, the lab-made photoreactor allows the utilization of different sources of irradiation with distinct wavelengths. Performance tests for production of gold nanoparticles showed reproducibility and equal efficiency as compared to the literature. Also, the photoreactor powered with UV-A and UV-C as sources of irradiation can be used for modulation of the reduction degree of graphene oxide.</p></div

Enhanced performance of 3D printed graphene electrodes after electrochemical pre-treatment : role of exposed graphene sheets

3D printing has been reported as a remarkable technology for development of electrochemical devices, due to no design constraints, waste minimization and, most importantly, fast prototyping. The use of 3D printed electrodes for electroanalytical applications is still a challenge and demand efforts. In this work, we have developed low-cost and reproducible 3D-printed graphene electrodes for electrocatalytic detection of dopamine. Electrocatalytic features were enhanced after electrochemical pre-treatment. The oxidation and reduction at different potential ranges, in 0.1 mol L-1 phosphate buffer solution (pH = 7.4), are used to modulate the structural and morphological characteristics of the electrodes. Since, the electrochemical properties of the electrodes, including electron transfer kinetic and the electrocatalytic activity, are strongly influenced by electronic properties and the presence of functional groups. Raman spectroscopy, SEM and AFM microscopes and electrochemical techniques were used to characterize the 3D electrodes before and after the electrochemical pre-treatments. Finally, the performances of the 3D-printed graphene electrodes were evaluated towards dopamine sensing. The best performance was achieved by oxidation at + 1.8 V vs. SCE for 900 s and reduction from 0.0 V to -1.8 V vs. SCE at 50 mV s(-1). The proposed sensor presented linear response from 2.0 mu mol L-1 to 10.0 mu mol L-1, with detection limit of 0.24 mu mol L-1281837848CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP459923/2014-5; 408985/2016-0não tem2013/22127-2; 2016/21070-5; 2017/23960-0The authors acknowledge the financial support by Fundo de Apoio ao Ensino, à Pesquisa e à Extensão - Universidade Estadual de Campinas, FAEPEX-UNICAMP (grant#2824/17), CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) (grant#459923/2014-5 and grant#408985/2016-0), São Paulo Research Foundation, FAPESP (grant#2013/22127-2, grant#2016/21070-5 and grant#2017/23960-0) and the National Institute of Science and Technology in Complex Functional Materials (CNPq-MCT/FAPESP). This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. The authors are grateful to Prof. Richard Landers (Institute of Physiscs – UNICAMP) for XPS measurement