Influence of the polymer concentration on the electroluminescence of ZnO nanorod/polymer hybrid light emitting diodes

The effects of the polymer concentration on the performance of hybrid light emitting diodes (LEDs) based on zinc oxide nanorods (ZnO NRs) and poly(9,9-dioctylfluorene) (PFO) was investigated. Various characterization techniques were applied to study the performance of the PFO/ZnO NR hybrid LEDs fabricated with various PFO concentrations. The fabricated hybrid LEDs demonstrated stable rectifying diode behavior, and it was observed that the turn-on voltage of the LEDs is concentration dependent. The measured room temperature electroluminescence (EL) showed that the PFO concentration plays a critical role in the emission spectra of the hybrid LEDs. At lower PFO concentrations of 2-6 mg/ml, the EL spectra are dominated by blue emission. However, by increasing the concentration to more than 8 mg/ml, the blue emission was completely suppressed while the green emission was dominant. This EL behavior was explained by a double trap system of excitons that were trapped in the β-phase and/or in the fluorenone defects in the PFO side. The effects of current injection on the hybrid LEDs and on the EL emission were also investigated. Under a high injection current, a new blue peak was observed in the EL spectrum, which was correlated to the creation of a new chemical species on the PFO chain. The green emission peak was also enhanced with increasing injection current because of the fluorenone defects. These results indicate that the emission spectra of the hybrid LEDs can be tuned by using different polymer concentrations and by varying the current injected into the device

Distance, View Angle and Blink Rate Working with a Smartphone

Maģistra darbs ir uzrakstīts latviešu valodā uz 43 lapaspusēm, Tas satur 37 attēlus, 3 tabulas, 4 pielikumus un 49 atsauces uz literatūras avotiem. Mērķis: noskaidrot, kā tuvuma darba uzdevumi (lasīšana, spēles spēlēšana) ietekmē skatīšanās attālumu, skata leņķi un mirkšķināšanas biežumu, un novērtēt viedtālruņa lietošanas paradumus. Metode: pirmajā daļā 8 dalībnieki viedtālrunī veica lasīšanas un spēles uzdevumu, otrajā daļā 53 dalībnieki aizpildīja aptauju par viedtālruņa lietošanas paradumiem. Rezultāti: uzdevuma veids un ilgums līdz 20 min neietekmēja darba attālumu, skata leņķi un mirkšķināšanu darbā ar viedtālruni. Lielāks skata leņķis uz leju ir saistīts ar samazinātu mirkšķināšanas biežumu. Vidējais viedtālruņa lietošanas ilgums ir 4 h dienā.Master thesis is written in Latvian. It contains 43 pages, 37 figures, 3 tables, 4 attachments and 49 references. Purpose: find out how near visual tasks (reading, playing a game) affects the viewing distance, viewing angle, and blinking frequency, and assess smartphone usage habits. Methods: In the first part, 8 participants completed a reading and game task on a smartphone, in the second part, 53 participants completed a questionnaire on smartphone use. Results: The type and duration of the task up to 20 min did not affect the working distance, viewing angle and blinking when working with a smartphone. A larger viewing angle downwards is associated with a reduced blinking frequency. The average usage time of a smartphone is 4 h a day. Key words: working distance, viewing angle, blinking, ODSI index, smartphone

Effect of the polymer emission on the electroluminescence characteristics of n-ZnO nanorods/p-polymer hybrid light emitting diode

Hybrid light emitting diodes (LEDs) based on zinc oxide (ZnO) nanorods and polymers (single and blended) were fabricated and characterized. The ZnO nanorods were grown by the chemical bath deposition method at 50A degrees C. Three different LEDs, with blue emitting, orange-red emitting or their blended polymer together with ZnO nanorods, were fabricated and studied. The current-voltage characteristics show good diode behavior with an ideality factor in the range of 2.1 to 2.27 for all three devices. The electroluminescence spectrum (EL) of the blended device has an emission range from 450 nm to 750 nm, due to the intermixing of the blue emission generated by poly(9,9-dioctylfluorene) denoted as PFO with orange-red emission produced by poly(2-methoxy-5(20-ethyl-hexyloxy)-1,4-phenylenevinylene) 1,4-phenylenevinylene) symbolized as MEH PPV combined with the deep-band emission (DBE) of the ZnO nanorods, i.e. it covers the whole visible region and is manifested as white light. The CIE color coordinates showed bluish, orange-red and white emission from the PFO, MEH PPV and blended LEDs with ZnO nanorods, respectively. These results indicate that the choice of the polymer with proper concentration is critical to the emitted color in ZnO nanorods/p-organic polymer LEDs and careful design should be considered to obtain intrinsic white light sources

Bacteriophage-derived dsRNA (Larifan) impact on melanoma growth in mouse models

Melanoma ir ļaundabīgs audzējs, kas veidojas galvenokārt ādā no tur esošajiem melanocītiem. Melanomai ir raksturīga strauja slimības gaita un agrīna metastazēšanās. Tā ir rezistenta pret standarta terapeitiskajām metodēm. Ievērojamais nesenais progress melanomas ārstēšanā arī nav devis gaidītos rezultātus, tāpēc joprojām tiek meklēti jauni melanomas ārstēšanas paņēmieni. Larifan ir bakteriofāga izcelsmes dsRNS (bf-dsRNS), kas iegūta biotehnoloģiskā ceļā no ar bakteriofāgu inficētām E.Coli šūnām. Tai piemīt spējas inducēt interforus (IFN), un tā tiek veiksmīgi pielietota kā pretvīrusu līdzeklis ar retām blakusparādībām. Larifan piemīt arī pret- audzēju aktivitāte. Maģistra darba mērķis bija noskaidrot Larifan ietekmi uz primāro audzēju un uz melanomas metastazēšanos B16 melanomas peļu modelī. Noskaidrots, ka Larifan kavē plaušu metastāžu veidošanos B16 peļu melanomas modelī un Larifan darbība visdrīzāk realizējas caur IFN sistēmu. Vislabākos rezultātus primārajā melanomas modelī deva Larifan ievadīšana intraperitoneāli. Interesanti, kas ap primārajiem audzējiem veidojās saistaudu kapsula, kuras esamība varēja ietekmēt terapijas iznākumu. Darbs izstrādāts Latvijas Biomedicīnas pētījumu un studiju centrā laika posmā no 2018. gada septembra līdz 2020. gada maijam. Atslēgas vārdi: melanoma, Larifan, dsRNS, audzējs, metastāzes, B16 šūnasMelanoma is a type of skin cancer that begins in melanocytes – melanin producing cells. Melanoma is characterized by rapid development of the disease and early metastasis. It is resistant to standard therapeutic methods. Recent progress in the treatment of melanoma has not brought the expected results, so new treatments are still required. Larifan is a heterogeneous population of dsRNA molecules, which has been isolated from E.coli cells infected with RNA bacteriophage f2 mutant. It is mostly known for its ability to induce type (I) interferons (IFNs) and it is used as antiviral agent with rare side effects. Nonetheless, it has also been shown to exhibit an anti-tumoral effect in some tumour models. The aim of the master’s thesis was to elucidate the effect of Larifan on primary tumors and melanoma metastasis in a mouse model of B16 mouse melanoma. The results showed that Larifan inhibits the development of lung metastases in the B16 mouse melanoma that is likely mediated by the IFN system. Intraperitoneal administration of Larifan gave the best results in the primary melanoma model. We have observed a connective tissue capsule formed around the primary tumors, the presence of which could affect the outcome of the treatment. The research for the master’s thesis was carried out at the Latvian Biomedical Research and Study Centre from September 2018 till May 2020. Key words: melanoma Larifan, dsRNA, tumor, metastasis, B16 cells

Effect of the polymer emission on the electroluminescence characteristics of n-ZnO nanorods/p-polymer hybrid light emitting diode Effect of the Polymer Emission on the Electroluminescence Characteristics of n-ZnO Nanorods/p-Polymer Hybrid Light Emitting D

Abstract Hybrid light emitting diodes (LEDs) based on zinc oxide (ZnO) nanorods and polymers (single and blended) are fabricated and characterized. The ZnO nanorods were grown by the chemical bath deposition method at 50 o C. Three different LEDs, either with blue emitting, orange-red emitting or their blended polymer together with ZnO nanorods were fabricated and studied. The current-voltage characteristics show good diode behavior with ideality factor in the range of 2.1 to 2.27 for all the three devices. The electroluminescence spectrum (EL) of the blended device has an emission range from 450nm to 750nm, due to the intermixing of the blue emission generated by the poly(9,9-dioctylfluorene) denoted as PFO with orange red emission produced by the poly(2-methoxy-5(20-ethyl-hexyloxy)-1,4-phenylenevinylene) 1,4-phenylenevinylene) symbolize as MEH PPV combined with the deep band emission (DBE) of the ZnO nanorods i.e. it covers the whole visible region and manifested as white light. The CIE colour coordinates showed bluish, orange-red and white emission from the PFO, MEH PPV and blended LEDs with ZnO nanorods, respectively. These results indicate that the choice of the polymer with proper concentration is critical to the emitted colour in ZnO nanorods/p-organic polymers LEDs and careful design should considered to obtain intrinsic white light sources

Efficient catalytic effect of CuO nanostructures on the degradation of organic dyes

An efficient catalytic effect of petals and flowers like CuO nanostructures (NSs) on the degradation of two organic dyes, methylene blue (MB) and rhodamine B (RB) were investigated. The highest degradation of 95% in CuO petals and 72% in flowers for MB is observed in 24 h. For RB, the degradation was 85% and 80% in petals and flowers, respectively for 5 h. It was observed that CuO petals appeared to be more active than flowers for degradation of both dyes associated to high specific surface area. The petals and flower like CuO NSs were synthesized using the chemical bath method at 90 °C. The grown CuO NSs were characterized using scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD).funding agencies|Advanced Functional Materials (AFT) grant at Linkoping University, Sweden||MUST University AJK, Pakistan||</p

Phase Retrieval of Vitreous Floaters in Presence of Aberrations

Maģistra darbs ir uzrakstīts latviešu valodā uz 45 lapaspusēm. Tas satur 34 attēlu, 4 tabulas, un 46 atsauces uz literatūras avotiem. Darba mērķis: Izvērtēt, kā optiskās sistēmas parametri ietekmē stiklveida ķermeņa apduļķojumu fāzes noteikšanu optiskās sistēmas aberāciju klātbūtnē. Metode: Aberāciju/apduļķojumu simulācijas, optisko parametru ietkmes izvērtēšana MATLAB vidē. Rezultāti un analīze: Apduļķojumi ir rekonstruējami aberāciju klātbūtnē. Ja trokšņa un fona amplitūda ir vienāda, fons kvalitāti pazemina vairāk. Bitu dziļuma pazemināšana samazina trokšņa un fona efektu. Datu ieguves biežuma palielināšana uzlabo rekonstrukcijas kvalitāti. Secinājumi: Troksnis, bitu dziļums, fons, datu ieguves biežums ietekmē apduļkojumu fāzes noteikšanu.Master thesis is written in Latvian on 45 pages. It contains 34 images, 4 tables, 46 references to literature sources Purpose: To evaluate how optical systems affects detemination of vitreous floater phase in optical system aberration presence. Methods: Aberration/floater simulation, evaluation of different optical systems in MATLAB. Results and analysis: Vitreous floaters can be retrieved in presence of aberrations. If the amplitude of noise and background is equal, the background compromises the quality of the phase more. Lowering the bit depth reduces the effect of noise and background. Increasing the oversampling ratio improves the quality of the phase. Conclusion: Noise, bit depht, oversampling, background affects determination of floater phase

CuO nanoflowers as an electrochemical pH sensor and the effect of pH on the growth

Well-crystallized flower-shaped cupric oxide (CuO) nanostructures composed of thin leaves have been synthesized by simple low-temperature chemical bath method and used to fabricate pH sensor. We examined the effect of the pH on the growth of the CuO nanostructures, by changing the pH of the precursor solutions different morphologies of the CuO nanostructures were obtained. CuO nanoflowers have recently become important as a material that provides an effective surface for electrochemical activities with enhanced sensing characteristics. The proposed sensor exhibited a linear electrochemical response within a wide pH range of (2-11). The experimental results (time response, electrochemical activity, reproducibility, absorption spectra, and XRD) indicate that the CuO nanoflowers can be used in pH sensor applications with enhanced properties

Zinc oxide nanorods/polymer hybrid heterojunctions for white light emitting diodes

Zinc oxide (ZnO) with its deep level defect emission covering the whole visible spectrum holds promise for the development of intrinsic white lighting sources with no need of using phosphors for light conversion. ZnO nanorods (NRs) grown on flexible plastic as substrate using a low temperature approach (down to 50 degrees C) were combined with different organic semiconductors to form hybrid junction. White electroluminescence (EL) was observed from these hybrid junctions. The configuration used for the hybrid white light emitting diodes (LEDs) consists of two-layers of polymers on the flexible plastic with ZnO NRs on the top. The inorganic/organic hybrid heterojunction has been fabricated by spin coating the p-type polymer poly (3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT : PSS) for hole injection with an ionization potential of 5.1 eV and poly(9, 9-dioctylfluorene) (PFO) is used as blue emitting material with a bandgap of 3.3 eV. ZnO NRs are grown on top of the organic layers. Two other configurations were also fabricated; these are using a single MEH PPV (red-emitting polymer) instead of the PFO and the third configuration was obtained from a blend of the PFO and the MEH PPV. The white LEDs were characterized by scanning electron microscope, x-ray diffraction (XRD), current-voltage (I-V) characteristics, room temperature photoluminescence (PL) and EL. The EL spectrum reveals a broad emission band covering the range from 420 to 800 nm, and the emissions causing this white luminescence were identified.Original Publication:Magnus Willander, Omer Nur, Siama Zaman, A Zainelabdin, Nargis Bano and I Hussain, Zinc oxide nanorods/polymer hybrid heterojunctions for white light emitting diodes, 2011, JOURNAL OF PHYSICS D-APPLIED PHYSICS, (44), 22, 224017.http://dx.doi.org/10.1088/0022-3727/44/22/224017Copyright: Iop Publishing Ltdhttp://www.iop.org

Influence of pH, Precursor Concentration, Growth Time, and Temperature on the Morphology of ZnO Nanostructures Grown by the Hydrothermal Method

We investigated the influence of the pH value, precursor concentration (C), growth time and temperature on the morphology of zinc oxide (ZnO) nanostructures. The pH of the starting solution was varied from1.8 to 12.5. It was found that the final pH reaches an inherent value of 6.6 independently of the initial pH solution. Various ZnO structures of nanotetrapod-like, flower-like, and urchin-like morphology were obtained at alkaline pH (8 to 12.5) whereas for pH solution lower than 8 rod-like nanostructures occurred. Moreover, we observed the erosion of the nanorods for a pH value less than 4.6. By changing the concentrations the density and size were also varied. On going from a high (C &gt; 400mM) to lower (C &lt; 25mM) C, the resulted ZnO nanostructures change from a film to nanorods (NRs) and finally nanowires (NWs). It was also found that the length and diameter of ZnO NRs follow a linear relation with time up to 10 hours, above which no further increase was observed. Finally the effect of growth temperature was seen as an influence on the aspect ratio.funding agencies|advanced Functional Material project Sweden|