PHOTOACOUSTIC AND PHOTOELECTROCHEMICAL CHARACTERIZATION OF TiO2 PHOTONIC CRYSTAL SENSITIZED WITH CdSe QUANTUM DOTS

電気通信大学200

HUBUNGAN ANTARA KELENTUKAN TOGOK DAN KOORDINASI MATA DAN TANGAN TERHADAP KETEPATAN PUKULAN ROUND THE HEAD DROP SHOT DALAM PERMAINAN BULUTANGKIS DI KLUB FIK UNIVERSITAS NEGERI JAKARTA

Tujuan penelitian ini adalah untuk mengetahui (1) Hubungan antara kelentukan togok (X1) dengan ketepatan pukulan round the head drop shot (Y), (2) Hubungan antara koordinasi mata dan tangan (X2) terhadap ketepatan pukulan round the head drop shot (Y), (3) Hubungan antara kelentukan togok (X1) dan koordinasi mata dan tangan (X2) secara bersama terhadap ketepatan pukulan round the head drop shot (Y). Penelitian ini dilaksanakan pada bulan Juni 2014 di Hall A Fakultas Ilmu Keolahragaan Universitas Negeri Jakarta. Penelitian ini menggunakan metode deskriptif dengan menggunakan analisis korelasi dan regresi. Populasi berjumlah 30 orang dengan menggunakan total sampling. Pengambilan data tes kelentukan togok menggunakan alat ukur Trunk Extension Meter. Untuk tes koordinasi mata dan tangan menggunakan alat ukur tes koordinasi mata dan tangan. Sedangkan untuk tes ketepatan pukulan round the head drop shot menggunakan alat ukur drop shot test. Teknik analisis statistik yang digunakan adalah dengan tehnik korelasi sederhana dan regresi ganda dan dilanjutkan dengan uji t pada taraf signifikasi α 0,05. Hasil analisis data menunjukkan bahwa (1) Terdapat hubungan yang berarti antara kelentukan togok (X1) terhadap ketepatan pukulan round the head drop shot (Y) yang ditunjukkan dengan koefisien korelasi ry1 = 0,61 (α = 0,05) dan koefisien determinasi = 0,37 yang berarti jumlah sumbangannya adalah 37%. (2) Terdapat hubungan yang berarti antara koordinasi mata dan tangan (X2) terhadap ketepatan pukulan round the head drop shot (Y) yang ditunjukkan dengan koefisien korelasi ry2 = 0,38 (α = 0,05) dan koefisien determinasi = 0,14 yang berarti jumlah sumbangannya adalah 14%. (3) Terdapat hubungan yang berarti antara kelentukan (X1) dan koordinasi mata dan tangan (X2) terhadap ketepatan pukulan round the head drop shot (Y) yang ditunjukkan dengan koefisien korelasi ry12 = 0,8 (α = 0,05) dan koefisien determinasi = 0,64 yang berarti jumlah sumbangannya adalah 64%

Low-Cost Flexible Nano-Sulfide/Carbon Composite Counter Electrode for Quantum-Dot-Sensitized Solar Cell

Cu2S nanocrystal particles were in situ deposited on graphite paper to prepare nano-sulfide/carbon composite counter electrode for CdS/CdSe quantum-dot-sensitized solar cell (QDSC). By optimization of deposition time, photovoltaic conversion efficiency up to 3.08% was obtained. In the meantime, this composite counter electrode was superior to the commonly used Pt, Au and carbon counter electrodes. Electrochemical impedance spectra further confirmed that low charge transfer resistance at counter electrode/electrolyte interface was responsible for this, implied the potential application of this composite counter electrode in high-efficiency QDSC

Wiring of Photosystem II to Hydrogenase for Photoelectrochemical Water Splitting.

In natural photosynthesis, light is used for the production of chemical energy carriers to fuel biological activity. The re-engineering of natural photosynthetic pathways can provide inspiration for sustainable fuel production and insights for understanding the process itself. Here, we employ a semiartificial approach to study photobiological water splitting via a pathway unavailable to nature: the direct coupling of the water oxidation enzyme, photosystem II, to the H2 evolving enzyme, hydrogenase. Essential to this approach is the integration of the isolated enzymes into the artificial circuit of a photoelectrochemical cell. We therefore developed a tailor-made hierarchically structured indium-tin oxide electrode that gives rise to the excellent integration of both photosystem II and hydrogenase for performing the anodic and cathodic half-reactions, respectively. When connected together with the aid of an applied bias, the semiartificial cell demonstrated quantitative electron flow from photosystem II to the hydrogenase with the production of H2 and O2 being in the expected two-to-one ratio and a light-to-hydrogen conversion efficiency of 5.4% under low-intensity red-light irradiation. We thereby demonstrate efficient light-driven water splitting using a pathway inaccessible to biology and report on a widely applicable in vitro platform for the controlled coupling of enzymatic redox processes to meaningfully study photocatalytic reactions.This work was supported by the U.K. Engineering and Physical Sciences Research Council (EP/H00338X/2 to E.R. and EP/G037221/1, nanoDTC, to D.M.), the UK Biology and Biotechnological Sciences Research Council (BB/K002627/1 to A.W.R. and BB/K010220/1 to E.R.), a Marie Curie Intra-European Fellowship (PIEF-GA-2013-625034 to C.Y.L), a Marie Curie International Incoming Fellowship (PIIF-GA-2012-328085 RPSII to J.J.Z) and the CEA and the CNRS (to J.C.F.C.). A.W.R. holds a Wolfson Merit Award from the Royal Society.This is the final version of the article. It first appeared from ACS Publications via http://dx.doi.org/10.1021/jacs.5b0373

The violent youth of bright and massive cluster galaxies and their maturation over 7 billion years

In this study, we investigate the formation and evolution mechanisms of the brightest cluster galaxies (BCGs) over cosmic time. At high redshift (z ∼ 0.9), we selected BCGs and most massive cluster galaxies (MMCGs) from the Cl1604 supercluster and compared them to low-redshift (z ∼ 0.1) counterparts drawn from the MCXC meta-catalogue, supplemented by Sloan Digital Sky Survey imaging and spectroscopy. We observed striking differences in the morphological, colour, spectral, and stellar mass properties of the BCGs/MMCGs in the two samples. High-redshift BCGs/MMCGs were, in many cases, star-forming, late-type galaxies, with blue broad-band colours, properties largely absent amongst the low-redshift BCGs/MMCGs. The stellar mass of BCGs was found to increase by an average factor of 2.51 ± 0.71 from z ∼ 0.9 to z ∼ 0.1. Through this and other comparisons, we conclude that a combination of major merging (mainly wet or mixed) and in situ star formation are the main mechanisms which build stellar mass in BCGs/MMCGs. The stellar mass growth of the BCGs/MMCGs also appears to grow in lockstep with both the stellar baryonic and total mass of the cluster. Additionally, BCGs/MMCGs were found to grow in size, on average, a factor of ∼3, while their average Sérsic index increased by ∼0.45 from z ∼ 0.9 to z ∼ 0.1, also supporting a scenario involving major merging, though some adiabatic expansion is required. These observational results are compared to both models and simulations to further explore the implications on processes which shape and evolve BCGs/MMCGs over the past ∼7 Gyr

CdSe量子ドットによるTiO2逆オパール電極の光増感と太陽電池への応用

近年、深刻化する環境問題やエネルギー資源問題の解決策の一つとして、太陽電池の開発が活発に行われている。現在の太陽電池の主流はシリコン（Si）系太陽電池であるが、原料供給や製造工程の複雑性、高コストなどが、依然問題となっている。そのなかで、製造プロセスが簡便で、安価に作製可能な色素増感太陽電池が注目されている。現在、色素増感太陽電池で用いられている増感剤は主に有機色素系が適用され、数多くの研究が進行しているが、新たな増感剤の候補として半導体量子ドットが大きな注目を集めている。半導体量子ドットの特徴として、①光吸収係数が大きい、②双極子モーメントが大きく電荷分離が急速に進行する、③粒径を制御することで光吸収領域を任意に設定することが可能、④多重励起子生成による量子効率の増大が期待される、といった有機色素系には無い特徴を持っている。また、TiO2基板電極においては、従来の不規則性ナノ粒子系の代わりに、規則性ナノ構造を持つ逆オパール構造のTiO2電極を適用し、それに伴う光電流の向上が期待できる。本研究ではこれらの特徴をふまえ、逆オパール構造TiO2光電極を作製し、増感剤としてCdSe量子ドットを適用した系を対象とし、光吸収や分光増感特性および光励起キャリアの過渡応答特性、さらに光電変換特性の評価を行い、高効率太陽電池への応用について検討した。本論文ではまず逆オパール構造TiO2光電極の作製とその基本構造と各特性（光吸収、光透過、光反射と光電流量子変換効率(IPCE)スペクトル、および過渡光電流応答特性）について論じた。ポリスチレン(PS)ラテックス粒子の自己組織化によるオパール状のテンプレートを作製し、TiCl4を充填前駆体として適用し、TiO2逆オパールナノ構造電極を形成した。Ｘ線粉末回折測定から作製されたTiO2逆オパールナノ構造はanatase構造を持っていることが分かった。透過スペクトルと拡散反射スペクトルから、フォトニック結晶（すなわち、逆オパール構造）に特有の光子の存在することができない領域であるフォトニックバンドギャップ(PBG)の存在が確認された。光音響（PA）分光法によって測定した光吸収スペクトルから、TiO2逆オパールのバンドギャップが3.2eVであることが確認された。過渡光電流応答から得られたTiO2逆オパールの電子拡散係数は従来の不規則性ナノ粒子TiO2電極のより大きいことが判明した。次に、CdSe量子ドットのTiO2逆オパール電極への吸着、さらにCdSe量子ドットの構造とCdSe量子ドット吸着したTiO2逆オパール電極の各特性（光吸収とIPCEスペクトル）について調べた。CdSe量子ドットの吸着には、CdSO4溶液、 N(CH2COONa)3溶液、Na2SeSO3溶液を混合した液にTiO２電極を浸し、一定温度で浸漬時間をパラメータとしてCdSe量子ドット吸着を行った。光吸収スペクトルから、CdSe量子ドットが吸着時間の増加と共に成長することが確認できた。PAスペクトルの肩の位置をCdSe量子ドットの第一励起エネルギーと仮定し、有効質量近似法からCdSe量子ドットの平均粒径を見積ったところ、吸着時間の増加と共にCdSe量子ドットのサイズが4nmからおよそ7 nmまで成長したことが分かった。IPCEスペクトルから、CdSe量子ドットによるTiO2逆オパール電極の分光増感が確認できた。さらに、光励起キャリアのダイナミクスについて調べた。光励起キャリアのダイナミクスの評価には過渡回折格子（TG）法を適用した。TG応答特性から、CdSe量子ドットにおける光励起電子とホールのダイナミクスを同時に測定することに成功した。その結果より、CdSe量子ドットにおける光励起ホールが2ps以内に緩和し、光励起電子が数10psから数100psまで緩和することが判明した。さらに、ガラス基板に吸着したCdSe量子ドットとTiO2逆オパールに吸着したCdSe量子ドットでの光励起電子の緩和時間の比較から、CdSe量子ドットからTiO2への電子移動速度を測定できた。最後に、CdSeを吸着したTiO2逆オパール電極の光電変換特性について調べた。半導体量子ドット表面への適切な修飾（ZnSとFの吸着）により、光電変換特性（短絡電流、開放電圧、fill factor、光電変換効率）が向上したことを見出した。過渡電圧応答測定より、表面修飾による表面欠陥の減少が示唆された。さらに、適切な対極の適用やCdSの吸着により、最高の光電変換効率が3.7%になった。この結果は、半導体量子ドット増感太陽電池では比較的に高い値である。Recently, dye-sensitized solar cells (DSSCs) has been attracted much interest in replacing silicon solar cells due to its low cost and simple fabrication method. The improvement of the performance of dye-sensitized solar cell (DSSC) must be achieved by considering the morphology of TiO2 film and the choice of sensitizers. TiO2 inverse opal could offer a promising solution in search for enhancing the light harvesting efficiency of dye-sensitized solar cell (DSSC) due to its large interconnected pores for better penetration of dye and photon localization in the red edge of photonic band gap for significant enhancement of dye absorption. In view of sensitizers, semiconductor quantum dots (QDs) have attracted much attention as dye substitute due to its tunable optical properties to maximize the solar absorption and capability of carrier multiplication through impact ionization.In this study, TiO2 inverse opal with its interconnected marcroporous structure and CdSe quantum dots (QDs) having tunable optical properties were investigated to be potential as novel light harvesting system. Inverse opals TiO2 electrodes could be replicated from colloidal latex crystals through the simple and relative fast bottom up method with only using one precursor solution, i.e. TiCl4 in methanol solution. CdSe QDs were then chemically adsorbed on inverse opal TiO2 electrodes through chemical bath deposition method. The photosensitization of TiO2 inverse opal with CdSe QDs adsorption was mainly studied by characterizing its optical absorption, photocurrent and photoexcited carrier dynamics. Moreover, its application to solar cell was introduced resulting efficient QD-sensitized solar cell.Grown CdSe QDs in situ on TiO2 inverse opal cause the red-shift in optical absorption and photocurrent properties. The higher energy of first excitation energy for each adsorption times relative to the band gap of bulk CdSe shows the occurrence of quantum confinement effect. The optimum photocurrent for certain adsorption times describes the appropriate condition for sufficient carrier generation, electron injection at CdSe/TiO2 interface and hole injection at CdSe/electrolyte interface (affected by the porous size in TiO2 inverse opal to allow the penetration of the electrolyte across the matrix).As the initial mechanism in photosensitization providing the vital comprehension of charge separation, ultrafast carrier dynamics in CdSe QD-adsorbed TiO2 inverse opal was characterized by transient grating technique. By comparing the measurement in air and electrolyte, the simultaneous detection of photoexcited hole and electron dynamics in CdSe QDs was successfully detected. The hole decay was found to be faster than the electron decay, that is in opposite to the mechanism of usual dye-sensitized solar cells. By changing the substrate, from TiO2 to glass, the hole decay time in the faster process is almost constant and the slower decay time with respect to electron changed greatly due to the electron injection from CdSe to TiO2 which does not occur in case of glass substrate. Thus the electron injection from CdSe QD to the TiO2 electrode could be measured. Furthermore, for same CdSe QDs and larger quantity of adsorbed CdSe QDs (forming larger cluster of CdSe QDs), different decay times were observed indicating the dominance of the role of CdSe-CdSe interfaces in carrier dynamics. These CdSe-CdSe interfaces provide the carrier transport along the clusters of CdSe QDs and this phenomena should be accounted in the ultrafast carrier dynamics overall.In sensitized solar cell application, TiO2 inverse opal structure matched very well with in situ growth of CdSe QD allowing the sufficient quantity of QD to absorb solar light on thinner electrode towards high efficiency. Relative to the CdSe QD-sensitized TiO2 nanocrystalline solar cells, CdSe QD-sensitized TiO2 inverse opal solar cells typically have higher open circuit voltage and fill factor. The former indicates the larger fraction of electron injection at TiO2 inverse opal surfaces rather than the common TiO2 nanocrystalline surfaces thus highly increasing the quasi Fermi level in TiO2 inverse opal conduction band. The latter implies the better penetration of electrolyte through the entire TiO2 electrode due to its macroporous structure resulting in the efficient hole transfer to the electrolyte. Moreover, the photovoltaic performances enhanced significantly by considering the surface modification on QD-sensitized TiO2 inverse opal electrode. By means of surface modification, the reduction of surface state was achieved in which confirmed by transient photovoltage. Further improvement could be achieved by using the proper porous counter electrode with large surface area against the used polysulfide electrolyte. Finally a power conversion efficiency of about 3.7% has been attained, under solar illumination of 100mW/cm2. This value is relatively high for QD-sensitized solar cells.電気通信大学200