Analysis of Photodetector Based on Zinc Oxide and Cesium Lead Bromide Heterostructure with Interdigital Metallization

In this thesis, photodetector based on the zinc oxide and cesium lead bromide hetero structure were fabricated and characterized. Zinc oxide (ZnO) nanoparticles were synthesized using solution processing and cesium lead bromide (CsPbBr3) thin film was synthesized using two step deposition method. Three phonon modes were obtained by the Raman spectroscopy of ZnO nanoparticles. X-ray diffraction spectra of ZnO exhibits five exciton peaks which denotes that the synthesized ZnO structure was of good crystallinity with wurtzite hexagonal phase. The absorbance spectrum of ZnO shows the bandgap (Eg) in the order of 3.5 eV that aligns with reported results. The photoluminescence and the absorbance technique were used to measure the Eg of CsPbBr3 in the order of 2.33 eV and 2.37 eV respectively which means the results are in good agreement. The current voltage (I-V) graph exhibits that due to the electron transfer from CsPbBr3 to ZnO under illuminated light, the photocurrent was increased by a factor 2 greater than the dark current under the bias voltage of 6 V. Impulse time response of the photodetector was observed by measuring the current under light on and light off condition with an interval of 10 seconds. The photodetector was fabricated using the conventional wet etching lithography. Interdigital metallization structures were used with Au electrodes having 10µm gaps. The detectivity of the photodetector was measured to be 3.8 × 1011 cm / Hz2 W from the I-V measurement. Under 10 µW light illumination the device showed good photo responsivity of 14.99 A/W. The fabricated photo detectors demonstrated excellent stability. This project explains that ZnO/CsPbBr3 hetero structure is a promising candidate for high performance photodetector

Saussurian Structuralism in Linguistics

This research article focuses on the basic assumptions about structuralism as proposed by Ferdinand Saussure through his ideas of structure, language signs, synchronic and diachronic study of language and langue and parole. It also incorporates the criticism on Saussurean thought from different intellectual quarters.  The background view of the life of Saussure and his intellectual legacy and attempts have been attempted to explain in simple terms before indulging into the technicalities of the topic

Design of Visible Light Driven Bismuth based Catalysts for Degradation of Organic Pollutants

This Ph.D. thesis deals with the synthesis, immobilization of bismuth-based nanostructures and their photocatalytic evaluation for degradation of organic pollutants mainly dyes, with the aim to optimize synthesis and photo-evaluation conditions by focusing the practical application of heterogeneous photocatalysis. Initially, various bismuth based single structures α-Bi2O3, Bi5O7NO3 and heterostructures α/β-Bi2O3, β-Bi2O3/Bi5O7NO3 were synthesized by a simple and scalable route i.e. thermal decomposition of precursor salt. Properties such as crystallinity, composition, morphology and optical parameters were tuned by simply varying the calcination temperature. Heterostructures of α/β-Bi2O3, β-Bi2O3/Bi5O7NO3 are well crystallized, formed stable composites (originated from single precursor salt) and eventually improved the stability of β-Bi2O3 (a metastable form) in the heterojunction structure. Single structures and heterostructures were evaluated for photodegradation of various dyes (differ in chemical structures and ionic behaviors) under visible and UV light. Test were conducted on single dyes or mixed solution of 2/3 dyes to assess the photocatalytic mechanism and kinetics when dealing the mixed effluent. From the obtained results, it was observed that α/β-Bi2O3 and β-Bi2O3/Bi5O7NO3 heterostructures have higher photocatalytic response due to efficient cascade of electrons and holes within the tuned heterojunction and band alignments. Moreover, different dyes interact differently with the photocatalyst and resulted in changed kinetics, while mechanism of degradation depended upon their ionic behavior. Furthermore, during degradation of mixed solution; dyes that have higher interaction (with photocatalyst) and low absorptivity preferentially degraded earlier. Afterwards, α/β-Bi2O3 were used to investigate and distinguish coexisting processes during photocatalysis: (i) intense adsorption, (ii) dye photobleaching and sensitization assisted photodegradation and (iii) partial or complete mineralization. It was found that some dyes with Azo (N=N) and sulphonic groups have intense adsorption over photocatalyst surface and discoloration could occur without photocatalysis. Further, it was revealed that under controlled conditions, the other coexisted processes hardly occur during photocatalysis. Moreover, indigo carmine (IC) dye was found appropriate for preliminary photo-evaluation because its discoloration/removal process could be directly associated with photocatalytic oxidation by analyzing some identified spectral changes in UV-vis absorbance spectrum. Moreover, it was highlighted that dye chromophoric groups react readily and are easily attacked by the originated photocatalytic reactive species and partially mineralized, while further degradation of resulted intermediates containing phenyl groups, became more difficult to oxidize or reduce to achieve complete mineralization. In addition, to investigate and identify the mechanism and the path of photodegradation of the investigated dyes, two approaches were used: 1) the photo-evaluation of dyes in presence of quenchers of hole, atomic oxygen and hydroxyl radical i.e. triethyl amine (TEA), P-benzoquinone (BQ) isopropanol (IP) and, respectively and 2) Evolution of O2 after water oxidation. From the experimental results it was observed, that the photocatalytic activity eventually reduced in presence of quenchers as they quench the originated reactive radical species. Moreover, evolved O2 during water splitting confirmed that electrons and holes are well separated and able to generate reactive oxygen and radical species for photodegradation and partial mineralization of dyes. Thereafter, the work was focused to tackle the challenges of powder photocatalyst recovery and to explore a competing route, i.e. immobilized fixed support. Glass, steel mesh and sintered silica were used for photocatalyst immobilization to solve the problems associated to photocatalyst recovery, mass limitation and low interaction of pollutants with fixed photocatalyst supports. The immobilization/deposition of β-Bi2O3 over each support, was achieved by pneumatic spray pyrolysis and subsequent calcination at 450 °C. During photo-evaluation of different β-Bi2O3 immobilized supports; deposited sintered silica exhibited higher activity and competing response to β-Bi2O3 powder. The improved activity of sintered silica was associated to the rough, porous and hydrophilic nature of silica that have facilitated in providing higher interaction of deposited β-Bi2O3 films with dye molecules. Furthermore, β-Bi2O3 deposited sintered silica exhibited improved performance for photodegradation and mineralization of various dyes of different chemical structures and ionic behaviors and cyclic stability up to 3 cycles. Then, the work was focused to obtain single structure ferromagnetic bismuth ferrite (BiFeO3) and its heterostructure (BiFeO3/Fe2O3/Bi2Fe4O9); as they have the advantage of easy magnetic separation from aqueous solution. The single structure BiFeO3 and its heterostructures were obtained by using Sol-Gel method, in which precursor solution, containing dissolved Bi(NO3)3:5H2O and Fe(NO3)3:9H2O were preheated and calcined at 500°C with and without addition of Polyethylene Glycol (PEG) and NaOH in the precursor solution. From the XRD and UV-vis DRS analysis it was observed that addition of PEG and NaOH, assisted to obtain single nanostructure BiFeO3, simply by enabling the particles polymerization and inhibiting the formation of other compounds like Fe2O3 and Bi2Fe4O9. It was revealed that single phase BiFeO3 is antiferromagnetic in nature and have very low photocatalytic response, due to the low energy band gap and high electron and holes recombination rate. On the other hand, BiFeO3/Fe2O3/Bi2Fe4O9 heterostructure displayed high magnetic saturation and exhibited improved photoactivity. This is due to a low electrons and holes recombination rate because of tuned band alignment and charge transfer within the heterojunction interfaces. Cyclic stability and photocatalytic performance of BiFeO3/Fe2O3/Bi2Fe4O9 were found almost similar during photodegradation of various dyes up to 3 cycles. At the end, detailed analyses of the efficient heterostructure α/β-Bi2O3 and promising β-Bi2O3 immobilized silica were made, for the evaluation of bulk single and mixed dye solutions under natural sunlight and at varying IC dye concentrations. It was found that the mechanism and the photodegradation kinetics were almost similar amongst lab conditions and during sunlight irradiation and for bulk solutions of single and mixed dyes. Moreover, the experienced phenomena of the degradation and achieved kinetic rate at varying IC concentration were almost alike for both α/β-Bi2O3 and deposited β-Bi2O3 sintered silica. These results revealed that deposited β-Bi2O3 sintered silica could have the promising potential over α/β-Bi2O3 or any other powder photocatalyst under solar light irradiation. Moreover, cyclic stability and the photoactivity of both α/β-Bi2O3 and deposited β-Bi2O3 silica were almost identical up to 3 cycles

Website Design and Localisation: A Comparison of Malaysia and Britain

This study aims to explore the local cultural values on Malaysian and British websites selected from different sectors. In recent years, a number of studies have addressed the issue of local culture in website design, but most of the studies have focused on USA representing western cultures, whereas Chinese and Japanese cultures have been the main focal point of Asian cultures. This study intends to fill this gap, focusing on less-debated cultures: Malaysia and Britain. It applies Hofstede’s individualism/collectivism, and power distance, and Hall’s high/low-context cultural dimensions, and analyses how these cultural values are reflected in Malaysian and British websites. A content analysis of the websites highlights considerable differences in representing local cultural values on the local websites

Optimization of depth-based routing for underwater wireless sensor networks through intelligent assignment of initial energy

Underwater Wireless Sensor Networks (UWSNs) are extensively used to explore the diverse marine environment. Energy efficiency is one of the main concerns regarding performance of UWSNs. In a cooperative wireless sensor network, nodes with no energy are known as coverage holes. These coverage holes are created due to non-uniform energy utilization by the sensor nodes in the network. These coverage holes degrade the performance and reduce the lifetime of UWSNs. In this paper, we present an Intelligent Depth Based Routing (IDBR) scheme which addresses this issue and contributes towards maximization of network lifetime. In our proposed scheme, we allocate initial energy to the sensor nodes according to their usage requirements. This idea is helpful to balance energy consumption amongst the nodes and keep the network functional for a longer time as evidenced by the results provided

Enhanced Wi-Fi Security of University Premises Using MAC Address and Randomly Generated Password

Many solutions are available for setting up wireless home networks to get internet connectivity working as quickly as possible. It is also quite risky as numerous security problems can result. Today’s Wi-Fi networking products do not always help the situation as configuring their security features, and they can be time-consuming.  In this paper, an improved security protocol is proposed for University premises, which is a combination of the process of MAC address filtering and random password generation. If the MAC address match, then the server will send a randomly generated password to the client. As a result, the whole network will face fewer intruders, and the security will be of top-notch. The proposed security solution was compared with the existing four security methods. The proposed solution has universality as the device and software needed for it is available all over the world

“All about Love”: How would bell hooks teach fashion design?

This paper introduces a PhD project which draws on theories from Black and Women of Colour feminists to develop anti-racist fashion design pedagogies. These pedagogical experiments demonstrate the value of Black and Women of Colour feminist scholarship for fashion design education through its call for the decolonization of pedagogy. Feminist scholarship emphasises the role of everyday life and ordinary experiences which can have the potential to disrupt hegemonic thinking. Such experiences could help shape new fashion design pedagogies and culture. I will suggest how using bell hook’s conception of “love” could also be taken up by fashion design educators to encourage students to explore points of connection and disconnection between different cultures, histories and experiences. hook’s notion could, I will also suggest, foster students’ active awareness of how local and global cultures and histories might be more creatively interwoven to create a design process that resists stereotyping, appropriation and racist forms of representation

A novel 96-microwell-based high-throughput spectrophotometric assay for pharmaceutical quality control of crizotinib, a novel potent drug for the treatment of non-small cell lung cancer

;Este estudo descreve o desenvolvimento e a validação de um novo ensaio espectrofotométrico em larga escala em 96 micropoços para o controle farmacêutico de crizotinibe (CZT), novo fármaco para o tratamento de câncer de pulmão de células não pequenas. Examinamos a reação entre o CZT e o 4-sulfonato de 1,2-naftoquinona, um reagente cromogênico. Obteve-se, em meio alcalino (pH 9), produto vermelho, com absorção máxima (λ;max;) em 490 nm. Examinamos a estequiometria da reação e propusemos mecanismo de reação. Este, segundo nosso conhecimento, é o primeiro estudo para descrever reação de desenvolvimento de cor para o ensaio proposto. A reação foi realizada em placas de 96 micropoços e mediu-se a absorbância do produto colorido utilizando-se leitor de absorbância a 490 nm. Sob condições otimizadas de reação, a lei de Beer, que mostra a correlação entre a absorbância e a concentração de CZT, foi obedecida na faixa de 4-50 µg/poço, com coeficiente de correlação apropriado (0,999). Os limites de detecção e de quantificação foram, respectivamente, 1,73 e 5,23 µg/poço. O ensaio mostrou alta precisão e exatidão. O ensaio proposto foi aplicado com sucesso para a determinação de CZT em cápsulas e é prático e válido para a aplicação de rotina em laboratórios de controle farmacêutico.;;This study describes the development and validation of a novel 96-microwell-based high throughput spectrophotometric assay for pharmaceutical quality control of crizotinib (CZT), a novel drug for the treatment of non-small cell lung cancer. We examined the reaction between CZT and 1,2-naphthoquinone-4-sulphonate, a chromogenic reagent. A red-colored product showing a maximum absorption peak (λ;max;) at 490 nm was produced in an alkaline medium (pH 9). We examined stoichiometry of the reaction and postulated the reaction mechanism. To our knowledge, this is the first study to describe a color-developing reaction for the proposed assay. The reaction was performed in a 96-microwell plate, and the absorbance of the colored product was measured using an absorbance reader at 490 nm. Under optimized reaction conditions, Beer's law, which shows a correlation between absorbance and CZT concentration, was obeyed in the range of 4-50 µg/well with an appropriate correlation coefficient (0.999). The limits of detection and quantification were 1.73 and 5.23 µg/well, respectively. The assay showed high precision and accuracy. The proposed assay was applied successfully for the determination of CZT in capsules. Thus, the assay proposed in this study is practical and valuable for routine application in pharmaceutical quality control laboratories.