M.Eng. / The need and problem was originated from the trends of the earths dwindling energy resource. As time progresses humans are becoming more aware of need to use so called “alternative energy sources” to alleviate the main energy converters i.e. power stations. The student was tasked with investigating the thermal performance of a solar powered refrigeration cycle (prototype) that could: produce enough refrigeration effect that it replaces the standard home vapour compression unit, used for cooling or freezing of foods, heats up a geyser sufficiently to have hot water for a common house hold, has excess energy to heat or cool liquid or air based environments and has the potential to lower the electrical bill of a house. The introductory step was to obtain the thermo fluid properties of aqua ammonia solutions. A setback came about when determining the aqua ammonia properties. There were too many conflicting properties being yielded by six different authors. In an attempt to gain confidence in only one author a comparison table was prepared. The table compared the six authors to each other. By looking at all the values compared it brought great clarity to the problem. When continuing the research into the fundamental law approach of solving for the cycle new findings were made. Initially very little comprehensive studies were done which explained in fundamental laws to solve for the absorption cycle. After extensive reviewing of a detailed study on how to solve for absorption refrigeration cycles, then it was able to begin improving on the thermo – fluid design of the cycle. As cycle and component design began to progress the train of thought began to steer in a direction. Each component needed to be detail designed. The advantage of having each component specifically catered for in the cycle design was that it would increase the cycle efficiency. In this way it would ensure that during the concept generation phase the functioning of each component was clear, thereby enabling a clear understanding of how components would compliment each other in a cycle. A mode of solving for the cycle was to endeavour that all parameters could be calculated unambiguously, with the aid of computerisation. Testing was carried out on a real life commercial thermal siphoning machine in order to realistically understand how absorption refrigeration works and gain experience. At the end of the study the most important result is that the dissertation research shows strong evidence that it will be possible to create a device which can fulfil the four tasks listed above. Another result is a program which is a refined cycle design of the pump absorption type refrigeration. The program solves for points along the cycle. Lastly it was found that even though EES was the simpler program to use for aqua ammonia solution properties it was the only program which catered for sub cooling and super heating.

This thesis studies the optimal design for a photovoltaic-powered medium-head (30 meters) water pumping system, with the emphasis on improving the efficiency and reducing the maintenance requirements of the electrical subsystem. The reduction of maintenance requirements is realized by replacing the conventional brush-type permanent magnet dc motor with a brushless dc (BLDC) motor. Different BLDC motor control techniques such as position-sensorless operation, sinusoidal and trapezoidal excitations are investigated. The improvement in efficiency is achieved by maximizing the output power from the photovoltaic array and by minimizing the losses in various parts of the electrical sub-system. A microprocessor-based double-loop maximum power tracking scheme is developed for maximization of the photovoltaic array output power. Over 99% utilization factor is achieved for a typical clear day regardless of the season of the year. The system losses are minimized mainly by performing loss analysis and selecting most suitable switching topologies and switching components. Experimental results show that the combined converter-motor efficiency is comparable to those of high-efficiency brush-type dc motor systems. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The amount of traditional energy sources are finite and the ecological impact of continuing to produce energy using fossil fuels will only exacerbate the carbon footprint. It is for these reasons that photovoltaic modules are becoming a larger and more necessary part the world's electricity production paradigm. Photovoltaic (PV) semiconductor modules are grouped into three categories. 'First generation' monocrystalline and polycrystalline silicon modules that consist of pn junctions created via the addition of impurities known as dopants. Almost 85% of solar cells produced at this time are `first generation' and it is the high production costs of silicon PV modules that motivated the search for new methods and materials to use as PV cells. 'Second generation' PV modules consist of semiconductor thin films. The 'second generation' PV modules in production at this time are copper indium gallium diselenide (CIGS), copper indium gallium (CIG), amorphous silicon (a-Si), and cadmium telluride (CdTe). The 'third generation' PV modules consist of dye-sensitized and organic materials. Thin films use less material, have less stringent production parameters and less waste, making thin films cost effective. In this investigation, solar cells were prepared using un-doped Group II-VI semiconductor thin films that exploit differences in bandoffsets to form effective p-n heterojunctions as a viable low cost alternative to doping. The thin films were deposited by thermal evaporation upon glass substrates coated with indium tin oxide (ITO). A layer of aluminum formed the back contact. Various configurations of the solar cells were produced including: ITO/CdS/CdSe/Al, ITO/ZnTe/CdSe/Al, ITO/CdTe/CdSe/Al, ITO/ZnTe/CdTe/CdS/Al. The solar cells produced have been characterized to determine thin film internal resistances, quantum and 'wall-plug' efficiencies, as well as I-V and spectral response. The open circuit voltage, short circuit current density, fill factor, and efficiency of our best devices were 0.26 V, 4.6 mA, 27.5 and 0.4% respectively. Additional device optimization should be possible and should improve these results. Solar cell design based on band-offset is an effective method for predetermining likely PV structures, while future investigation using Group II-VI semiconductor nanowires and nanorods and employing epitaxial films are likely to enhance the efficiency.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for degree of Master of Science in Chemistry / The mandate for renewable energy sources to replace the current reliance on fossil fuels as a primary energy source has recently attracted a lot of research interest. The research has also focussed on bringing the technologies that take into consideration the goal of reducing environmental pollution. Consequently, approaches using photovoltaic (PV) technologies have been a promising arena to tackle the problem facing energy sources. Recently, more focus has been placed on improving the power conversion efficiency (PCE) of PV devices, such as organic and/or organic-inorganic hybrid perovskite solar cells. Therefore, in this work two different materials were applied in two independent PV devices, namely organic and/or organic-inorganic hybrid perovskite solar cells. One study employed nitrogen doped broken hollow carbon spheres (N-bHCSs), with an aim of enhancing the electronic properties of the P3HT:PCBM active layer of an organic photovoltaic (OPV) solar cell. N-bHCSs were successfully synthesized using a horizontal chemical vapour deposition method (H-CVD) employing a template-based method and the carbon was doped using in-situ and ex-situ doping techniques. Pyridine, acetonitrile and toluene were used as both carbon and nitrogen precursors. The dispersity of the SiO2 spheres (i.e. templates) was found to play a role on the breakage of the N-bHCSs. Incorporation of the N-bHCSs into the P3HT:PCBM active layer was found to enhance the charge transfer and this led to less recombination of photogenerated charges in the interface between the donor and acceptor. The current-voltage (I-V) characteristics of the ITO/PEPOT:PSS/P3HT:PCBM:N-bHCSs/Al solar cell devices revealed an increased chargetransport distance due to increased electron density by n-type doping from the N-bHCSs. The second study employed the organic-inorganic hybrid perovskite (CH3NH3PbI3) material as a light harvesting layer in an ITO/PEDOT:PSS/CH3NH3PbI3/PC6BM/Al solar cell device. Initially, the device parameters were optimised to obtain the best performing device. These include parameters such as the degradation of the hybrid film as a function of time and air exposure. A rapid degradation was seen on the device after 24 h of air exposure which was accompanied by the decrease in the PV performance of the device. The degradation was visually seen by the formation of crystal grains (i.e. “islands”) on the perovskite film. / GR2019

This research project deals with the development of a methodology to analyse and design photovoltaic-based power systems. A microcomputer-based interactive photovoltaic (PV) performance analysis package has been developed. This package can be used for screening analysis of various sites, module characteristics and system configurations. Basic elements of this package include: ( i) resource assessment; ( ii) site analysis; (iii) technology assessment; (iv) optimization and choice of system configurations; and (v) life-cycle cost analysis. The resource assessment part of the package is used to estimate the hourly, daily and monthly global horizontal, fixed tilt and one-axis tracking insolation for any site under cloudless sky condition. Site elevation, latitude, longititude and Julian date information are used for this purpose. This insolation level determines the upper limit of possible irradiance at the site under consideration. This value can be adjusted on the basis of climatic conditions (e.g., occurrences of cloudy days and rainfall) prevailing in the area. The site analysis deals with the site's economic and environmental evaluation. The parameters involved in these evaluations are the total land area, the effective area of the site, the area of forest destroyed, the loss of use of the site, the total number of people who are affected by the project, the number of people who benefit from the project, and the purchase price of the site. The technology assessment part of the package deals with the process of creating electricity from solar energy. The D.C. power output of the array is determined by using the global irradiation, the manufacturer-supplied efficiency and dimensions of the module, and the total area of the array. The A.C. power can also be evaluated depending on the power conditioning unit (PCU) efficiency. The optimization and the choice of the system configuration part of the package is used for determining the most optimum use of the candidate site in terms of land availability, land cost and the best possible mix of various PV modules for optimizing the cost of the PV energy within the existing constraints. Finally a life-cycle cost analysis is performed which includes cost of operation, cleaning, maintenance, spare parts, tilting, module, module support, inverter, charge controller, backup system and energy storage. It also takes into consideration the lifetime of the inverter, charge controller, the module, the backup system and the energy storage system. This package has been applied to analyse the performance of various PV modules in two locations. One of the biggest advantages of this package is that it is based on TURBO PASCAL language and runs on the IBM-PC and compatible microcomputers. Thus it is very portable from one operating environment to another, and users can be trained in its application quite easily. / M.S.

A major issue encountered in the large scale use of Photovoltaic (PV) energy sources for the production of electricity is the variability of the resource itself. Extensive fluctuations of the PV generation may cause dynamic operational problems for an electric utility. In order to remedy this situation it is proposed that fuel cell power plants be operated in parallel with PV arrays. This hybrid operation will help to smooth out the fluctuating PV output. Because of its high ramping capability the fuel cell will be able to absorb such fluctuations. An overall methodology is presented to evaluate the PV system in a large utility. This methodology has two parts-planning and operation. The aim of the planning study is to determine the capacity credit of a PV system based on the loss of load probability (LOLP). Long term SOLMET data is used to determine the nature of available insolation at a particular site. The expected value of hourly insolation is used in the planning study. The aim of the operation study is to validate the results of planning study in the shorter operational time frame, and determine the fuel cell requirements and associated operating cost savings for each penetration level of PV. A technique to find the maximum penetration level of PV, without causing any economic penalty, is presented. It is found that the penetration level can be increased up to 15.62% of peak load by adding fuel cells to the system under consideration. The annual peak load for this system is taken as 6400 MW. It must be mentioned here that, similar evaluations for other systems may yield somewhat different results. This technique is general enough such that it can be used for other intermittent sources of generation as well. / Ph. D.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

A Thesis submitted for the faculty of Science at the University of Witwatersrand Johannesburg, in the fulfilment for the degree of Doctor of Philosophy in Chemistry. Johannesburg, November 2016. / The synthesis of carbon spheres (solid and hollow) for application in organic photovoltaics and chemical sensors is a means of using inexpensive and readily processable carbons to eliminate global warming and to monitor harmful gases. The synthesis conditions used to make solid carbon spheres can also be used to tailor their structural, paramagnetic and thermal properties. More so, the ability to tailor the morphology, surface, structural and electronic properties of the hollow carbon spheres by a templating method is an added advantage to their applicability in electronic devices. Solid carbon spheres were synthesized by a vertically oriented chemical vapor deposition (CVD) reactor using acetylene as a carbon source and argon or hydrogen as the carrier gas. The flow rates of the acetylene or carrier gases determined the particle sizes of the carbon spheres. Annealing of carbon spheres in hydrogen resulted in an increase in thermal stability, fewer defects and narrower paramagnetic signals relative to the carbon spheres annealed in argon gas. In contrast, carbon spheres annealed in argon exhibited an increase in the number of defects, a decrease in thermal stability and broader paramagnetic signals. Doped carbon spheres portrayed an increase in ID/IG ratios, a decrease in thermal stability and stronger paramagnetic signals due to the presence of defects induced by nitrogen. The N doped carbon spheres synthesized in H2 comprised of 48% pyridinic-N, 22% pyrrolic-N and 24% quaternary -N while the N doped spheres obtained in the presence of Ar had 17% pyridinic- N, 20% pyrrolic-N and 49% quaternary-N. The presence of a higher percentage of pyridinic- N confirms the presence of more edge defects in carbon spheres synthesized under H2 gas corroborating with the stronger paramagnetic signal observed from the ESR spectra. Consequently, a higher N/C ratio was exhibited in the N doped CSs obtained in the presence of H2 (4.96) than in the presence of Ar (3.68). This could be attributed to the presence of edge defects in carbon spheres synthesized in the presence of H2 gas. The induction of edge defects in carbon spheres in the presence of H2 gas without the aid of a metal catalyst opens a platform for regulating surface and catalytic reactions using H2 gas. Pristine and mesoporous SiO2 spheres were synthesized using a modified Stober method. Carbonization of the pristine SiO2, pristine SiO2@PVP, mesoporous SiO2 and mesoporous SiO2@PVP spheres was carried out using a bubbling method with toluene as the carbon source and argon as the carrier gas in a CVD reactor for 1 h. Upon SiO2 removal, hollow carbon nanostructures of varying morphologies were obtained. The polyvinylpyrrolidone (PVP) adsorption time, PVP concentration, SiO2 mesoporosity, SiO2 particle size dispersion, and carbonization time played a role in the formation of unique hollow carbon nanostructures; complete HCSs, broken HCSs, deformed HCSs, edge connected, open ended, wormlike and bubble-like HCSs. The mesoporous broken HCSs and open ended HCSs portrayed a hierarchical structure with a bimodal pore size distribution. The surface area properties of these materials and the ease of control of the carbon morphology gives an insight into the application of these materials as dye adsorbents. The effect of the size dispersion of Au@SiO2 sphere templates for the synthesis of hollow carbon structures was evaluated using a CVD nanocasting method. The diameter of the template, the presence of the gold nanoparticles and the amount of PVP determined the size, thickness and shape of the synthesized carbon nanostructures. Carbonization (and SiO2 removal) of Au@polydispersed silica spheres for 1 h gave a graphene-like HCS layer while longer times (2-4 h) gave nanotube like (or worm like) HCSs. These results highlight the potential use of Au@carbon core shell structures for the generation of few layered graphene-like unusual nanostructures. As a proof of concept, the wormlike carbon structures were incorporated in organic solar cells and found to give a measurable photovoltaic response. The incorporation of Au nanospheres and nanorods in a hole transport layer (PEDOT:PSS) of a solar cell device increased the current density and the photo-conversion efficiency of the device due to the local surface plasmon resonance and enhanced light scattering effects of gold. However, high series resistance and leakage currents were obtained due to barrier centres created by uneven dispersion of Au nanaorods within the polymer matrix. The performance of bulk heterojunction organic photovoltaic cells based on poly(3-hexylthiophene- 2,5-diyl) (P3HT) and 6,6-phenyl-C61-butyric acid methyl ester (PCBM) processed from chlorobenzene solution can be enhanced by solution heat treatment of the blend. The morphology of films spin coated from the heat treated blend solution reveals a more favourable diffusion of PCBM into the P3HT matrix than heating of the individual solutions separately. The films obtained from heat treated P3HT and PCBM solutions had a more homogeneous dispersion and enhanced light absorption than those obtained from solutions heat treated separately. There was a significant improvement in the performance for devices made from a solution heat treated blends relative to the non-treated blend; a maximum power conversion efficiency of 3.5% and a fill factor up to 43% was achieved under Air Mass 1.5 at 100 mW/cm2 illumination. This study also reports on the sensing characteristics of ammonia in humid environment by hollow carbon spheres, hollow carbon spheres-polyvinylpyrrolidone composite and annealed hollow carbon spheres, at 20°C and 40°C. For device fabrication, a surfactant assisted method was used to homogeneously disperse the hollow carbon spheres, allowing their deposition onto an interdigitated electrode by casting. An enhanced response and recovery time of the devices was observed at the higher working temperature. Annealing of the hollow carbon spheres resulted in a tremendous decrease in the humidity dependent ammonia sensing due to a decrease in the number of the oxygenated groups and defects in their structure. The presence of hydroxyl groups on the pristine hollow carbon sphere surface resulted in an enhanced proton conductivity. However, the ammonia sensitivity at high relative humidity in the pristine hollow carbon spheres is negligible due to the inhibition of ammonia adsorption sites by the high concentration of water molecules. The sensor response was investigated by varying both ammonia concentration and relative humidity, determining the topology of the response as a function of these two variables, and applying a tristimulus analysis in an attempt to determine the ammonia concentration independently of the relative humidity. This study demonstrates the critical role played by humidity and surface chemistry in the ammonia sensing properties of hollow carbon spheres. The studies reveal the day to day application of ammonia sensors, with temperature and humidity playing a critical role in the carbon based sensor response and recovery of the materials. These carbon based sensors that simultaneously measure ammonia and relative humidity could be applied in agricultural industries to monitor ammonia concentration in soils, fishponds and in food industries to monitor meat spoilage. / LG2017

As the rapid development of the applications of unconventional semiconductors in the 21th century, the new electronic and bioengineering revolutions based on solid state devices have become possible, that is facilitated through the understanding of electron or energy transfer process at the functionalized interfaces of organic semiconductors and two-dimensional (2D) materials. Especially in applications of photovoltaics and biosensors, the attributes of the interfaces play an important role in performance advancement. In this thesis, I have focused on the utilization of organic small molecule semiconductors as energy cascade materials to modify the interfaces between donor and acceptor of P3HT/PC₆₁BM binary organic solar cell, so as to improve the device performance. The charge transfer process at the interface of P3HT and functionalized graphene has also been investigated through P3HT/functionalized graphene blending photovoltaic devices. Moreover, I have concentrated on the interface of single layer MoS₂ and fluorescently-labeled DNA, where the electrons were transferred from fluorescent groups of DNA to MoS₂, resulting in fluorescence quenching. This quenching characteristic can be useful in other related biosensors. / In Chapter 1, an introduction to organic semiconductors and two-dimensional materials for applications in photovoltaics and biosensors has been presented. In Chapter 2, the experimental details used in this thesis have been discussed. / In Chapter 3, a novel small organic semiconductor molecule (CPA) with ambipolar attribute as an energy cascade material has been employed, to fabricate bulk heterojucntion solar cells. The organic photovoltaic devices with ternary structures, demonstrates a step of energy cascade to assist charge transfer between the electron-donating P3HT and electron-accepting PC₆₁BM. The ternary structure offers a distinct platform and an easily applicable approach to overcome shortcomings in P3HT-PC₆₁BM system by increasing the attainable product of short circuit current (JSC) and open circuit voltage (VOC). This ternary structure also retains the simplicity of a single processing step for photoactive layer. / In Chapter 4, to explore the potential of the p-type small organic semiconductor DTDCTB as energy cascade material in ternary blend bulk heterojunction (BHJ) solar cells, I have studied a BHJ system based on poly (3-hexylthiophene) (P3HT), [6,6]-phenyl C₆₁ butyric acid methyl ester (PC₆₁BM) and DTDCTB. This ternary structure demonstrates the improvement of power conversion efficiency (PCE) as compared to that of the binary devices composed of P3HT/PC₆₁BM alone. A systematic spectroscopic study was carried out to elucidate the underlying mechanism. Wavelength-dependent external quantum efficiency measurement confirmed the DTDCTB contribution to the increased photocurrent. Photoinduced spectroscopy and transient photovoltage measurements unambiguously revealed that the charges generated in DTDCTB were efficiently transferred to and transported in P3HT and PC₆₁BM. The results also suggested that despite the realization of cascade charge transfer, the bimolecular charge recombination process in the ternary system is still dominated by the P3HT/PC₆₁BM interface. / In Chapter 5, a simple method by using aryl diazonium salt reaction has been devised to achieve covalent bond formation by altering the hybridization of carbon atom in configuration of sp² to sp³. Afterwards the group of benzoic acid has been grafted onto pristine graphene, to open a band gap of this two-dimensional material. It was well functionalized, dissolved in organic solvents to provide the various of fabrication processes for electron devices. The LUMO of functionalized graphene below the LUMO of P3HT and close to that of PC₆₁BM indicates its suitability as an electron-acceptor for OPV applications. Then the bulk heterojunction solar cells composed of P3HT/functionalized graphene composite as active layer have been further prepared, achieving a PCE efficiency of 1.1%. / In Chapter 6, a novel MoS₂-based fluorescent biosensor for DNA detections via hybridization chain reactions (HCRs) has been demonstrated. MoS₂, as an emerging nanomaterial, has excellent fluorescence quenching ability and distinct adsorption properties for single- and double-stranded DNA. In the sensing method, MoS₂ nanosheets were used to suppress the background signal and control the “on” and “off” states of fluorescence emission of the detection system with and without the presence of the target DNA. In addition, the signal generation was amplified through the target-triggered HCRs between two hairpin probes. The utilization of MoS₂ and HCRs guaranteed the high sensitivity of the detection strategy with the detection limit of 15pM. The biosensor also exhibited very good selectivity over mismatched DNA sequences. The detection took place in solutions and requires only one “mix-and-detect” step. The high sensitivity, selectivity, and operational simplicity demonstrate that MoS₂ can be a promising nanomaterial for versatile biosensing. / In Chapter 7, I provide the conclusions and a brief prospect of the further development in ternary system of perovskite solar cells and in based-two dimensional materials micro-fluidic biological monitoring FET. / 對於二十一世紀，隨著人們對非传统半导体材料应用的發展有著迫切的需求，新的基於固態器件的電子工程和生物工程的革命正在悄然進行，這是基於對有機半導體材料和二維層狀材料的功能化的界面上發生的電子或者能量轉移的理解，特別是在太陽能電池器件和生物傳感器方面上的應用。本論文主要是關注與利用有機半導體小分子作為能級梯級材料去调节P3HT/PC₆₁BM二元有機光伏器件中給體與受體見的界面，從而得到更好性能的器件。同時也關注了P3HT和功能化的石墨烯界面上的電荷轉移，并通過P3HT/功能化石墨烯混合有機光伏器件來研究界面上的電荷轉移。另外，還關注了單層硫化鉬和螢光標記的DNA間的界面，在這個界面上DNA螢光基團的能量會轉移到二硫化鉬上從而導致螢光淬滅，並且應用這一淬滅特性在生物傳感上。 / 在第一章中，本論文對有機半導體和二維材料在光伏器件和生物傳感器件中的應用給出了一個簡單的介紹。第二章展示了論文涉及到的檢測方法。 / 在第三章中，本論文利用一種新型的具有雙極性的有機半導體小分子(CPA)作為能級梯級材料去製作異質結太陽能器件。這些具有三元體系結構的太陽能器件展示了能級梯級變化的過程，這個過程是為了改善電子給體P3HT和電子受體PC₆₁BM間的電荷轉移。這種三元體系結構提供了一種顯著而且簡單的方法來克服P3HT-PC₆₁BM二元體系的不足，并通過提高其短路電流和開路電壓的乘積來實現，同時保持簡單的一步光敏層的製作方式。 / 在第四章中，為了探索P型有機半導體小分子DTDCTB能否作為級聯材料在有機異質結太陽能器件中使用，本論文研究了三元體系包含P3HT，PC₆₁BM和DTDCTB的有機異質結太陽能器件。這種三元結構器件展現出更佳的性能對比與P3HT/PC₆₁BM二元體系器件。另外，三元體系中電荷轉移的內在機制通過一系列系統的光譜來闡明。光誘導光譜和瞬態光電壓測試明確的揭示了DTDCTB中產生的電荷會被有效的通過P3HT和PC₆₁BM傳輸走。這些結果還表明，儘管存在級聯電荷傳輸，但是雙分子間的電荷複合過程主要發生在P3HT/PC₆₁BM界面。 / 第五章提出一個簡單的通過使用芳香基重氮鹽反應的方法，實現了碳碳共價鍵合成的反應，這種反應是通過改變碳原子sp²雜化成sp³雜化的方式進行的，而且可以移植苯甲酸官能團到原味的石墨烯上來打開石墨烯的帶隙。石墨烯這種二維層狀材料通過明確的的功能化后，可以溶在有機溶劑中從而提供了其作為電子器件的製作工藝的多元化。功能化后的石墨烯的LUMO能級比P3HT的LUMO能級要低，並且接近于PC₆₁BM的LUMO能級，這一特性意味著功能化后的石墨烯作為電子受體在有機光伏器件中的應用是可行的。因此，本論文進一步展示了以P3HT和功能化后的石墨烯複合材料作為光敏層的異質結太陽能器件，並且其具有1.1%的光電轉化效率。 / 在第六章中，本論文提出了一種新型基於二硫化鉬的螢光生物傳感器，這一傳感器通過雜交連鎖反應(HCRs)應用於DNA檢測。二硫化鉬作為新興的納米材料，有著對單鏈或者雙鏈DNA的良好螢光淬滅和顯著的吸附特性。在此檢測方法中，二硫化鉬納米片被用來抑制背景信號，並且通過存在或者不存在目標DNA來控制檢測體系中螢光發射的開啟和閉合。另外，檢測信號通過兩個髮夾型DNA探針間的目標觸發的HCR方法放大。通過使用二硫化鉬和HCR實現了高靈敏度的檢測，其檢測極限是15pM。這個傳感器對於DNA的錯配具有良好的選擇性。這個檢測在溶解中進行，並且僅僅需要簡單的一步混合來實現。高的靈敏度、選著性和工藝簡單等特性表明了二硫化鉬這種納米材料可以在多種生物檢測中使用。 / 第七章三元體系鈣鈦礦結構光伏器件和基於二維材料微流生物檢測器件的應用。 / Ye, Lei. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2014. / Includes bibliographical references. / Abstracts also in Chinese. / Title from PDF title page (viewed on 04, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by Paolo Rava. / Ph.D.