Multi-dimensional carbonaceous composites for electrode applications

Abstract The objective of this thesis is to demonstrate multi-dimensional carbon nanotube (CNT) structures in combination with various active materials in order to evaluate their performance in electrode applications such as cold emitters, electric double-layer capacitors (EDLC), and electrochemical sensor/catalyst devices. As the host materials for other active materials, the construction of multi-dimensional CNT nanostructures in this thesis is achieved by two different approaches. In the first, direct growth of 3-dimensional carbon nanostructures by catalytic chemical deposition to produce filamentary carbon as well as vertically aligned forests was applied. The second route that was utilized encompassed the immobilization of CNTs from dispersions to form 2-dimensional surface coatings as well as self-supporting porous buckypapers. Carbonaceous nanocomposites of the active materials are obtained by a number of different methods such as (i) growing nanotubes and filamentous structures on porous Ni catalyst structures, (ii) impregnating CNTs with organic receptor molecules or with Pd nanoparticles, (iii) plating and replacing Cu with Pd on the nanotubes by chemical and galvanic reactions, (iv) annealing W evaporated on CNTs to form CNT-WC composites in solid-solid reactions and (v) reacting S vapor with W coated on CNTs to synthesize CNT-WS2 edge-on lamellar structures of the dichalcogenide in the vertically aligned CNT forests. The 3-dimensional carbon-Raney®Ni composite electrodes show reasonable specific capacitance of ~12 F·g-1 in electric double-layer capacitors as well as a low turn-on field (<1.0 V·µm-1) in field emitter devices. CNT-Nafion®-trifluoroacetylazobenzene coatings on glassy carbon electrodes outperform their Nafion®-trifluoroacetylazobenzene counterparts in electrochemical sensing of different amine compounds (e.g. 10 mM cadaverine, putrescine or ammonia). Cu and CuPd/buckypaper composites display catalytic activity in electrocatalytic oxidation of methanol in alkaline media. On the other hand, nanocomposites of WC and WS2 with aligned CNT forest exhibit a promising performance in hydrogen evolution reactions with an overpotential between -0.5 and -0.7 V at pH~1. In addition, these respective CNT forest aligned nanocomposites also demonstrate a novel method to obtain macroscopic 3-dimensional catalytic electrode assemblies. The results in this thesis elucidate the combination of carbon based nanostructures with organic and inorganic materials as a feasible and versatile approach to produce electrodes for several applications. The following studies of each active carbonaceous composite are expected to boost the technological innovation in relevant fields and initiate further development for commercial exploitation.Tiivistelmä Työn tavoitteena oli demonstroida moniulotteisia hiilinanoputkirakenteita (CNT), joihin yhdistetään erilaisia aktiivisia materiaaleja sekä arvioida niiden suorituskykyä elektrodisovelluksissa, kuten kenttäemitterissä, sähköisissä kaksoiskerroskondensaattoreissa ja sähkökemiallisissa anturi- ja katalyyttikomponenteissa. Moniulotteisten CNT-nanorakenteiden konstruoiminen muiden aktiivisten materiaalien isäntämateriaaliksi toteutettiin kahdella tavalla. Ensimmäisessä toteutuksessa sovellettiin katalyyttis-kemiallista pinnoitusta, jolla kasvatettiin suoraan kolmiulotteisia hiilinanorakenteita sekä kuitumaisena hiilenä että pystysuuntaan orientoituneina hiilinanoputkimetsinä. Toinen päämenetelmä oli hiilinanoputkien immobilisointi dispersioista kaksiulotteisiksi pinnoitteiksi ja itsetukeutuviksi huokoisiksi hiilinanoputkipapereiksi. Hiiltä sisältäviä aktiivisten materiaalien nanokomposiitteja valmistettiin useilla menetelmillä, kuten (i) kasvattamalla nanoputkia ja kuitumaisia rakenteita huokoisiin Ni-katalyyttirakenteisiin, (ii) kyllästämällä hiilinanoputkia orgaanisilla reseptorimolekyyleillä tai Pd-nanopartikkeleilla, (iii) pinnoittamalla ja korvaamalla nanoputkien päällä olevaa kuparia palladiumilla kemiallisten ja galvaanisten reaktioiden avulla, (iv) hehkuttamalla hiilinanoputkien pinnalle höyrystettyä wolframia (W) muodostamaan CNT-WC-komposiitteja kiinteä–kiinteä-reaktiolla sekä (v) antamalla rikkihöyryn reagoida W-pinnoitettujen hiilinanoputkien kanssa lamellaaristen CNT-WS2-kalkogenidirakenteiden syntetisoimiseksi pystysuuntaan orientoituneisiin CNT-metsiin. Kolmiulotteisilla hiili–Raney®Ni-komposiittielektrodeilla saavutetaan kohtuullinen ominaiskapasitanssi (~12 F·g-1) sähköisissä kaksoiskerroskondensaattoreissa ja pieni kytkeytymiskenttä (<1,0 V·μm-1) kenttäemitterikomponenteissa. CNT-Nafion®-trifluoroasetyyliatsobentseeni-pinnoitteet lasimaisilla hiilielektrodeilla ovat selvästi parempia erilaisten amiiniyhdisteiden (esimerkiksi 10 mM kadaveriini, putreskiini tai ammoniakki) sähkökemiallisessa havaitsemisessa kuin vastaavat Nafion®-trifluoroasetyyliatsobentseeni-pinnoitteet. Cu- ja CuPd-hiilinanoputkipaperikomposiitit osoittavat katalyyttistä aktiivisuutta metanolin sähkökatalyyttisessä hapettumisessa emäksisessä väliaineessa. Toisaalta WC- ja WS2-yhdisteiden ja orientoituneiden CNT-metsien muodostamat nanokomposiitit osoittavat lupaavaa suorituskykyä vedynmuodostamisreaktiossa -0,5…-0,7 V ylipotentiaalilla, ja nämä myös demonstroivat uutta menetelmää makroskooppisten kolmiulotteisten katalyyttisten elektrodirakenteiden toteuttamiseksi. Väitöskirjan tulokset osoittavat, että hiilipohjaisten nanorakenteiden ja orgaanisten/epäorgaanisten materiaalien yhdistäminen on toteuttamiskelpoinen ja monipuolinen lähestymistapa elektrodien valmistamiseksi useisiin sovelluksiin. Kunkin työssä esitetyn aktiivista hiiltä sisältävän komposiitin tutkimuksen odotetaan lisäävän kyseisen alan teknisiä innovaatioita ja synnyttävän lisää kehitystyötä tutkimuksen kaupalliseksi soveltamiseksi

Interfacial Engineering for Organic/Inorganic Hybrid Bulk－heterojunction and the Application in Photovoltaics

由於共軛高分子/無機奈米粒子混摻薄膜在其光伏應用中所展現的優異熱穩定性，此類有機/無機異質接面元件近年來更吸引許多關注。然而，較低的光電轉換效率是此系統在將來的發展以及商業化前的主要課題。因此，合適的製程方式以提高元件轉換效率是近來研究上所迫切需要的。本論文的研究動機在於展示不同的界面工程方法於高分子與無機奈米粒子間之作用，包括對於混摻薄膜表面形態的控制以及針對混摻薄膜內所使用的無機二氧化鈦奈米桿所採用的不同修飾方法。各種混摻薄膜性質的改變以及其在於光伏元件的應用將做為審視各種界面工程方法的依據。 為了能夠在有機無機混摻薄膜中獲得更佳的表面形態控制，於是具有自組裝行為的硬桿‒柔曲嵌段共聚高分子(P3HT‒b‒P2VP)分別做為供體材料以及添加物加入有機無機混摻薄膜。做為供體材料與二氧化鈦(TiO2)奈米粒子的應用中，其長程規則有序結構中可容納的二氧化鈦奈米粒子上限共聚高分子中的P2VP的重量百分比而有所不同，分別為10 wt% TiO2於57 wt% P2VP嵌段共聚高分子的層狀結構、20 wt% TiO2於75 wt% P2VP嵌段共聚高分子的柱體結構以及40 wt% TiO2於86 wt% P2VP嵌段共聚高分子的圓球結構。 此外，由於P3HT‒b‒P2VP各別嵌段對於共軛高分子P3HT (P3HT嵌段)以及二氧化鈦奈米桿(P2VP嵌段) 的良好混溶性，不同比例的P3HT‒b‒P2VP分別做為加工添加物被導入共軛高分子聚3-己基噻吩(P3HT)/二氧化鈦奈米桿混摻薄膜中。在導入1.50 wt% 的P3HT‒P2VP三元系統混摻薄膜中，縮小的共軛高分子P3HT結晶區域尺寸(從88.21 Å 縮小至 85.47 Å)以及較低的光激螢光強度皆表示P3HT‒b‒P2VP作為加工添加物皆能有效改善共軛高分子P3HT以及二氧化鈦奈米桿在混摻薄膜內部的自我團聚現象。 另一方面，各種針對無機奈米粒子的結晶度˴電性以及表面性質的改善方式也被展示於此論文中。經過熟化以及異質摻雜處理，二氧化鈦奈米桿的電子遷移率可分別從原本的6.21×10-5 cm2·V-1·s-1強化至5.27×10-4 cm2·V-1·s-1(熟化)以及2.33×10-4 cm2·V-1·s-1(異質硼摻雜)。另外，利用表面接附共軛修飾分子於無機奈米粒子上以覆蓋其表面晶格缺陷也被視為另一種可行的方法。因此，我們利用二次表面改質處理法，第一階段將三種不同的pyridine衍生物( pyridine, 2, 6‒Lutidine (Lut) and 4‒tert‒butylpyridine (tBP))分別在第一階段表面處理時做為表面改質溶劑以便於在二氧化鈦奈米桿的表面創造不同界面組織，並且幫助了解第二階段表面處理時共軛修飾分子(W4)於不同二氧化鈦奈米桿界面的接附行為。經過量化分析後，tBP被發現能夠有效去除原本存在二氧化鈦奈米桿表面的油酸分子，並且由於在第二階段表面處理時，二氧化鈦奈米桿所接附的共軛修飾分子(W4)數目與裸露的二氧化鈦表面空位有關。因此，經過tBP表面處理的二氧化鈦奈米桿其W4接附量可以達到0.62 mol%，此數值遠高於pyridine (0.38 mol%)以及Lut (0.19 mol%) 處理後的二氧化鈦奈米桿。另一方面，二氧化鈦奈米桿上的載子傳輸速率亦受到其接附的共軛修飾分子數量所影響，因此在二氧化鈦奈米桿溶液製備薄膜以及與P3HT混摻薄膜中，其電子遷移率的改善效果被發現與接附的共軛修飾分子(W4)成正相關。 最後，我們將採用各種界面工程方法所製備的聚三‒己基噻吩/二氧化鈦奈米桿有機無機混摻薄膜應用於光伏元件並且觀察其個別光電轉化效率。根據分別的參照組元件(聚三‒己基噻吩與pyridine處理後的二氧化鈦奈米桿混摻薄膜，其轉換效率約0.40%)，使用柔曲嵌段共聚物P3HT‒b‒P2VP作為加工添加劑以及各種應用於修飾二氧化鈦上的修飾方法，例如熟化、硼摻雜和tBP‒(W4)表面修飾處理，其光電轉化效率上的增幅分別可以達到186%, 31%, 79% 以及 240%。 本論文中所包含的實驗結果闡述了界面工程方法在高分子/無機奈米粒子混摻薄膜的光伏元件應用有著非常重要的效果。本論文所揭露的研究方向被期望能夠在其後續的研究、相關科技的創新以及更進一步的發展和商業應用扮演著承先啟後的角色。Since the good thermal stability of conjugated polymer/inorganic nanocrystal hybrids in the photovoltaic application, such organic/inorganic bulk‒heterojunction has attracted much attention in recent years. However, the limited power conversion efficiency is the main issue for further development and commercialization. As a result, adequate approaches to improve the photovoltaic performance are urgently required. The objective of this dissertation is to demonstrate different methodologies of interfacial engineering as well as morphology control between polymer and inorganic nanocrystals. The effects of each approach were evaluated by the properties of treated polymer/nanocrystal hybrid thin film and their corresponding photovoltaic performance. To have better morphology control in polymer/nanocrystal hybrid thin film, the rod‒coil block copolymers P3HT‒b‒P2VP with different molecular designs were used as donor materials. The loading limit of TiO2 nanoparticles is found highly correlated to the weight percentage of P2VP segment in the self‒assembled block copolymer (10 wt%, 20 wt% and 40 wt% accommodation limit of TiO¬2 nanoparticles for lamella (57 wt% P2VP), cylindrical (75 wt% P2VP) and spherical (86 wt% P2VP) ordered structures, respectively). In addition, since the good miscibility of block copolymer P3HT‒b‒P2VP to both conjugated homopolymer P3HT (P3HT segment) and TiO2 nanorods (P2VP segment), different small amounts of P3HT‒b‒P2VP was incorporated into the P3HT/TiO2 hybrid thin film as the processing additive for better morphology control. After adding 1.50 wt% P3HT‒b‒P2VP, the reduced P3HT crystalline domain size (from 88.21 Å to 85.47 Å) and low extinction intensity of photoluminescence in P3HT/TiO2/P3HT‒b‒P2VP ternary blend thin films indicate the aggregation of P3HT donor is reduced and the miscibility of TiO2 acceptor in P3HT is improved. On the other hand, techniques aim to improve the crystallinity, electrical properties as well as the surface characteristics of nanocrystals were also adopted in this dissertation. After different treatments such as post‒ripening process and heterogeneous doping of TiO2 nanorods, the electron mobility of corresponding treated nanorods are both significantly enhanced (5.27×10-4 and 2.33×10-4cm2·V-1·s-1 for boron‒doped and ripened nanorod, respectively) compared to the as‒synthesized nanorod (6.21×10-5 cm2·V-1·s-1). Moreover, capping conjugated modifier onto nanocrystal seems to be another feasible approach to cover the pristine surface defects. The existence of surface defect may trap charge carrier during the charge separation and transport. Accordingly, we adopted two-stage ligand exchange process on the surface of TiO2 nanorods: three different pyridine derivatives such as pyridine, 2, 6‒Lutidine (Lut) and 4‒tert‒butylpyridine (tBP) were applied as dispersion solvent in first stage surface modification to create distinct surface characteristics of TiO¬2 nanorod and elucidate the anchoring behavior of conjugated modifier on these surfaces in second stage modification. Additionally, the quantitative studies for category and anchoring amount of ligand on as‒synthesized and three different modified TiO2 nanorods were obtained by elemental analysis, in which the tBP and Lut were proven as the most effective solvent for oleic acid (OA) removal and ligand-anchoring during the ligand exchange process, respectively. After the second stage surface modification using conjugated modifier of 2‒cyano‒3‒(5‒(7‒(thiophen‒2‒yl)‒benzothiadiazol‒4‒yl)thiophen‒2‒yl)acrylic acid (W4), the capping amount is correlated to the number of unbounded sites on the surface of TiO2 nanorods. As a result, the TiO2‒tBP with the lowest amount of anchored ligands shows the highest attaching amount of W4, the bonded W4 number can be reached up to 0.62 mol% compared to those of other two modified TiO2 nanorods (0.38 and 0.19 mol% for TiO2‒Pyridine‒W4 and TiO2‒Lut‒W4, respectively). Additionally, the anchored W4 surface modifier on TiO2 nanorods would also improve the charge carrier transport in TiO2 percolated domains due to its conjugated nature. The enhanced electron mobility (i.e. electron is transported by TiO2 interpenetrating network in P3HT/TiO2 hybrid solar cell) in either solution‒cast TiO2 or hybrid thin film is observed in the sequence of μe, TiO2‒tBP‒W4 > μe, TiO2‒Pyridine‒W4 > μe, TiO2‒Lut‒W4 > μe, TiO2‒OA with the decreasing amount of anchored W4 modifiers. Last, the engineered P3HT/TiO2 nanorod hybrid film was fabricated into solar cell and then its photovoltaic performance was assessed. Compared to the reference hybrid thin film without any treatment (P3HT/TiO2‒Pyridine with about 0.40% of power conversion efficiency), the power conversion efficiency of P3HT/TiO2 nanorod hybrid solar cell are increased by 186%, 31%, 79% and 240% after the incorporation of P3HT‒P2VP additive, as well as ripened, B‒doped, and tBP‒W4 modified TiO2, respectively. The results in this work demonstrate the importance of interfacial engineering for polymer/nanocrystal hybrid thin film in photovoltaic application, and which are useful to boost the technological innovation for relevant commercial exploitation

Enhancing the Efficiency of organic hybrid solar cell by cooperating polysilic acid nanodots into hole transport layer PEDOT:PSS

聚二氧乙基塞吩 : 聚(磺酸苯乙烯) (PEDOT:PSS)由於具有良好的光穿透度以及導電性，因此常被拿來作為有機光電元件中的載子傳導材料。本篇將不同混摻物添加進入電洞傳導層PEDOT:PSS後，利用原子力探針顯微鏡探討其表面型態的變化以及PEDOT:PSS之間相分離的情況，並且使用空間電荷限制電流法 (space charge limited current method) 以及四點探針法 (four point probe method) 觀察加入不同添加物進入電洞傳導層後其電性變化，由於我們所使用的添加物-奈米點溶液是由溶劑四氫呋喃以及聚矽酸奈米粒子所組成。利用空間限制電流法，我們發現添加物的電洞阻擋的現象主要來自於溶劑四氫呋喃，而添加聚矽酸奈米粒子進入PEDOT:PSS後,其奈米粒子的表面電位可以有效屏蔽聚二氧乙基塞吩以及聚磺酸苯乙烯兩者之間的電荷，並且幫助電洞的傳導。除此之外我們也利用表面改質的方法，利用APTES置換奈米點上表面原本具有的氫氧根基團(PND-OH)而得到表面接附上較長鏈段基團且末端為胺根官能基的的奈米點(PND-NH2)。我們將不同的聚矽酸奈米粒子溶液添加到PEDOT:PSS中塗佈成膜後，應用到兩種有機太陽能電池P3HT/TiO2 以及P3HT/PCBM系統中。我們將表面接附不同官能基的奈米點添加到PEDOT:PSS電洞傳導層並且應用到P3HT/TiO2太陽能電池中，並且發現添加兩種奈米點都能夠有效提升P3HT/TiO2太陽能電池的元件效率，但是表面具有胺根基團的奈米點(PND-NH2)效率提升幅度較大，這可能是來自於此奈米點所具有的較高表面電位，如此一來加入表面具有胺根基團的奈米點(PND-NH2)可以更有效的屏蔽聚二氧乙基塞吩以及聚磺酸苯乙烯兩者之間的電荷。然而將兩種奈米點添加到P3HT/PCBM系統的電洞傳導層中，所得到的結果卻截然不同。這樣的結果顯示在電子以及電洞兩者遷移率較為平衡的P3HT/PCBM系統中，加入帶有正表面電位的奈米點以及負表面電位的奈米點，其電洞阻擋效果與電荷屏蔽效應兩者之間互相競爭，進而導致添加不同比例的奈米點後P3HT/PCBM元件出現效率增加或是降低兩種截然不同的情形。Due to the good transparency and conductivity of Poly(3,4ethylenedioxythiophene) -polystyrenesulfonic acid (PEDOT:PSS), it commonly used as carrier transport material in organic photovoltaic devices. In this work, morphology change and phase separation of different doped PEDOT:PSS film are studied by AFM to explore the influence of different additive in PEDOT:PSS hole transport layer. Otherwise, we also used different methods like space charge limited current and four point probe method to detect electric properties of corresponding doped PEDOT:PSS films. The additive, Polymeric nanodot (PND) solution is composed of solvent tetrahydrofuran (THF) and polysilic acid. The space limited charge current fitting curves revealed that hole-blocking effect was attributed from the solvent THF instead of polysilic acid, however the polysilic acid doped in PEDOT:PSS polymer complex could help the hole transport by inducing charge screening between PEDOT:PSS. We also applied these doped PEDOT:PSS layer into two different polymer solar cell : P3HT/TiO2 and P3HT/PCBM hybrid solar cell, the doping of PND-OH and PND-NH2 can enhance the power conversion efficiency of P3HT/TiO2, but in P3HT/PCBM solar cell system, PND-NH2 and PND-OH doped samples exhibited different characteristic. The reason for efficiency enhancement and reduction of different PND doping ratio in PEDOT:PSS layer was interesting, we thought the balance of electron and hole mobility in P3HT/PCBM system is better than P3HT/TiO2 system. The addition of particles of negative or positive surface potential would induce hole-blocking effect and charge screening effect between PEDOT and PSS. As the result, the performance of doped sample would change by the competition of above two effects decided by different ligand capped on PND and corresponding doping ratio in PEDOT:PSS

Effective real-time forecasting of inundation maps for early warning systems during typhoons

Accurate forecasts of hourly inundation depths are essential for inundation warning and mitigation during typhoons. In this paper, an effective forecasting model is proposed to yield 1- to 6-h lead-time inundation maps for early warning systems during typhoons. The proposed model based on Support Vector Machine (SVM) is composed of two modules, point forecasting and spatial expansion. In the first module, the rainfall intensity, inundation depth, cumulative rainfall and forecasted inundation depths are considered as model input for point forecasting. In the second module, the geographic information of inundation grids and the inundation forecasts of reference points are used to yield inundation maps for spatial expansion. The results show that the proposed model is able to provide accurate point forecasts at each inundation point. Moreover, the spatial expansion module is capable of producing accurate spatial inundation forecasts. Obviously, the proposed model provides reasonable spatial inundation forecasts, and is able to deal with the nonlinear relationships between inputs and desired output. In conclusion, the proposed model is suitable and useful for inundation forecasting

Acute encephalitis after COVID-19 vaccination: A case report and literature review

Vaccine-related immune responses are one of the causes of encephalitis. Vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) have been administered worldwide due to the ongoing global pandemic; cases of SARS-CoV-2 vaccination-related encephalitis were scarcely reported. An 82-year-old female was diagnosed with acute encephalitis following her first dose of vaccination with mRNA-1273 against SARS-CoV-2. The patient presented with fever and headache five days after vaccination, followed by behavior change 17 days after vaccination. Electroencephalographic recordings revealed focal slow waves in the right frontoparietal regions. Brain MRI revealed the signal change in the right middle and posterior temporal lobe. Cerebrospinal fluid analysis showed mildly elevated protein. She responded well to steroid pulse therapy and made a full recovery. The severity of the immune response following COVID-19 vaccination may be alleviated if adequate treatment is achieved. Physicians must be alert for encephalitis after vaccination to help ensure a favorable outcome