Optical Study of Ultrathin TiO2 Films for Photovoltaic and Gas Sensing Applications

TiO2 ultrathin films of thickness below 20 nm were deposited by reactive RF magnetron sputtering. The optical properties of TiO2 films were investigated by various optical techniques including UV-VIS-NIR spectroscopic ellipsometry. The Scanning Probe Microscopy (SPM) was used to determine thickness and surface roughness of the deposited films. The correlation between preparation conditions of ultrathin TiO2 films and their physical properties has been studied. The analysis of optical data revealed the parameters of deposited films and intrinsic properties of TiO2 material before and after annealing. We found that deposited layers were predominantly amorphous with high porosity at the top sample, and absence of porosity at the bottom of TiO2 layer. Annealing considerably improves structural order of the studied samples and the film transforms to the polycrystalline anatase phase. Also we evaluated the energy bandgap (about 3.1 eV – 3.2 eV) which increases after annealing (above 3.3 eV) and it is  close to the bandgap of anatase. DOI: http://dx.doi.org/10.5755/j01.ms.20.2.6328</p

Patogeninių mikroorganizmų identifikavimas elektronine nosimi

Rokas Bagdonas1, Rytis Rimdeika1, Algimantas Tamelis1, Mindaugas Kiudelis1, Andrius Olekas2, Daiva Senulienė2, Arūnas Šetkus21 Kauno medicinos universiteto klinikų Chirurgijos klinika,Eivenių g. 2, LT-50009, Kaunas2 Puslaidininkių fizikos institutas,Goštauto g. 11, LT-01108 Vilnius*El paštas: [email protected] Įvadas / tikslas Atlikdami įprastinius mikrobiologinius tyrimus, atsakymą apie infekcijos sukėlėją paprastai gauname per 48–72 val. Tačiau neretai toks laiko tarpas yra per ilgas, todėl visi nauji infekcijos diagnostikos metodai, leidžiantys anksčiau nustatyti žaizdos infekciją, kelia itin didelį susidomėjimą ir yra labai perspektyvūs. Mūsų eksperimentuose elektronine nosimi buvo tiriami kvapai, susiję su patogeninių mikroorganizmų augimu maitinamojoje terpėje. Mikroorganizmai buvo paimti nuo žaizdas dengiančių tvarsčių. Eksperimentams buvo išskirti Acinetobacter, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus patogeniniai mikroorganizmai. Metodai Atlikta 313 matavimų su skirtingais mikroorganizmais, išsėtais skirtingose terpėse, sauso ir 100% oro drėgnio sąlygomis. Palyginti elektroninės nosies varžos kitimo parametrai tiriant Acinetobacter, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus patogeninius mikroorganizmus sauso (n-119) ir 100% santykinio oro drėgnio sąlygomis (n-194). Rezultatai Bendras ištirtų mėginių skaičius buvo 194, jį sudarė skirtingų mikroorganizmų testavimas elektronine nosimi, naudojant 100% santykinio drėgnio nešančiojo sintetinio oro srautą. Iš visų testų mėginiams naudojant Acinetobacter spp. atlikti 48 matavimai, Staphylococcus aureus – 20, Pseudomonas aeruginosa – 65 ir Escherichia coli – 61 matavimas. Bakterijų kvapų 2, 4, 6 ir 7-ojo jutiklių atsakas statistiškai reikšmingai skyrėsi. Kiekvienam atvaizdui, įskaitant ir signalų matavimą bei jų matematinį apdorojimą, suformuoti buvo sugaišta maždaug 30–40 minučių. Išvados Elektroninės nosies varžos kitimo parametrai, diagnozuojant Acinetobacter, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus patogeninius mikroorganizmus, reikšmingai skiriasi ir leidžia identifikuoti skirtingus mikroorganizmus. Elektroninė nosis gali būti tinkamas ankstyvesnio infekcijos diagnozės nustatymo metodas. Reikšminiai žodžiai: elektroninė nosis, dujų jutikliai, žaizdų patogeniniai mikroorganizmai, ankstyvoji diagnostika, neinvazinė diagnostika Identification of pathogenic microorganisms by electronic nose Rokas Bagdonas1, Rytis Rimdeika1, Algimantas Tamelis1, Mindaugas Kiudelis1, Andrius Olekas2, Daiva Senulienė2, Arūnas Šetkus21 Kaunas Medical University Hospital, Department of Surgery,Eivenių str. 2, LT-50009, Kaunas, Lithuania2 Semiconductor Physics Institute,Goštauto str. 11, LT-01108 Vilnius, Lithuania*E-mail: [email protected] Background / Objective Performing the routine microbiological assays the answer about infectious agent usually comes out in 48–72 hours. However, such a long time interval generally is too long and therefore all new diagnostic methods enabling earlier identification of wound infection generate great interest and are thought to be very promising. In our experiments with electronic nose we analysed odours related to growth of pathogenic microorganisms in nutrient medium. Microorganisms were taken from the wound dressing. For the experiments there were isolated Acinetobacter, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus pathogenic microorganisms. Methods There were 313 measurements performed with different microorganisms from different mediums under the conditions of dry air and 100% air humidity. A comparison of changing parameters in electronic nose resistance was made in studying Acinetobacter, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus pathogenic microorganisms under the conditions of dry air (n-119) and 100% air humidity (n-194). Results Overall there were 194 specimens analysed in which different microorganisms were tested with electronic nose using 100% relative humidity carrying the flow of synthetic air. From all the specimens 48 measurements were performed using Acinetobacter spp., 20 – Staphylococus aureus, 65 – Pseudomonas aeruginosa, and 61 measurement with Escherichia coli. The response of gas sensors 2, 4, 6 and 7 evoked by bacteria odours varied statistically significant. Composing each image took about 30–40 minutes including measuring and mathematical processing of signals. Conclusions The changing parameters of electronic nose resistance vary significantly in diagnosing Acinetobacter, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus pathogenic microorganisms and it enables to identify different microorganisms. Electronic nose may be an appropriate method for the earlier diagnostics of the infection. Keywords: electronic nose, gas sensors, pathogenic microorganisms of the wound, early diagnostics, noninvasive diagnostic

Silicon Nanostructures For Efficient Light Absorption In Photovoltaic Devices

Porous silicon light trapping layers (por-Si LTL) were manufactured using electrochemical etching. Optical measurements have shown the improved por-Si LTL optical properties versus bulk silicon. The p-n junction was formed by boron diffusion from borosilicate glasses. Scanning Kelvin Force Microscopy (SKFM) and Tunnelling Atomic Force Microscopy (TUNA) techniques were used to determine the location of p-n junction in samples with porous silicon light trapping layers. DOI: http://dx.doi.org/10.5755/j01.ms.20.2.6326</p

Functionalization of α-synuclein fibrils

The propensity of peptides and proteins to form self-assembled structures has very promising applications in the development of novel nanomaterials. Under certain conditions, amyloid protein α-synuclein forms well-ordered structures – fibrils, which have proven to be valuable building blocks for bionanotechnological approaches. Herein we demonstrate the functionalization of fibrils formed by a mutant α-synuclein that contains an additional cysteine residue. The fibrils have been biotinylated via thiol groups and subsequently joined with neutravidin-conjugated gold nanoparticles. Atomic force microscopy and transmission electron microscopy confirmed the expected structure – nanoladders. The ability of fibrils (and of the additional components) to assemble into such complex structures offers new opportunities for fabricating novel hybrid materials or devices

Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy for Probing Riboflavin on Graphene

Graphene research and technology development requires to reveal adsorption processes and understand how the defects change the physicochemical properties of the graphene-based systems. In this study, shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) and graphene-enhanced Raman spectroscopy (GERS) coupled with density functional theory (DFT) modeling were applied for probing the structure of riboflavin adsorbed on single-layer graphene substrate grown on copper. Intense and detailed vibrational signatures of the adsorbed riboflavin were revealed by SHINERS method. Based on DFT modeling and detected downshift of prominent riboflavin band at 1349 cm&minus;1 comparing with the solution Raman spectrum, &pi;-stacking interaction between the adsorbate and graphene was confirmed. Different spectral patterns from graphene-riboflavin surface were revealed by SHINERS and GERS techniques. Contrary to GERS method, SHINERS spectra revealed not only ring stretching bands but also vibrational features associated with ribityl group of riboflavin and D-band of graphene. Based on DFT modeling it was suggested that activation of D-band took place due to riboflavin induced tilt and distortion of graphene plane. The ability to explore local perturbations by the SHINERS method was highlighted. We demonstrated that SHINERS spectroscopy has a great potential to probe adsorbed molecules at graphene

Macroporous Silicon Structures for Light Harvesting

Macroporous silicon light trapping layers on the surface of p-type substrates were manufactured by using electrochemical etching. Optical measurements have shown the decreased optical reflection as compared to bulk silicon. The p-n junction was formed by phosphorus diffusion from phosphosilicate glasses. Scanning Kelvin Force Microscopy technique was used to determine the location of p-n junction in samples with porous silicon layers.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5725</p

Influence of Growth Time and Temperature on Optical Characteristics and Surface Wetting in Nano-Crystalline Graphene Deposited by PECVD Directly on Silicon Dioxide

Unique electronic properties of graphene offer highly interesting ways to manipulate the functional properties of surfaces and develop novel structures which are sensitive to physical and chemical interactions. Nano-crystalline graphene is frequently preferable to crystalline monolayer in detecting devices. In this work, nano-crystalline graphene layers were synthesized directly on SiO2/Si substrates by plasma-enhanced chemical vapour deposition (PECVD). The influence of the deposition time and temperature on the characteristics of the structures were studied. The optical properties and evaporation kinetics of pure water droplets were analysed, along with arrangement and composition of the grown layers. The nano-crystalline graphene layers grown at 500 °C were characterised by the refraction index 2.75 ± 0.35 and the normalised excess Gibbs free energy density 0.85/γwater 10−4 m, both being similar to those of the monolayer graphene. The changes in the refraction index and the excess Gibbs free energy were related to the parameters of the Raman spectra and a correlation with the technological variables were disclosed