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"Zinc Oxide (ZnO) is an important semiconductor material due to its broad applications, such as in the fields of electronics, optoelectronics, photocatalysts, and solar cells. The main purpose of this work was to investigate the effect of pressure in post-hydrothermal treatment on crystallinity enhancement, crystallite growth, and band gap reduction of ZnO nanoparticles, which could be expected to improve their performance as the semiconductor oxide layer in the dye-sensitized solar cell application. For this purpose, ZnO nanoparticles have been successfully synthesized through the precipitation method, followed by a sequence of thermal treatments including drying, calcination, and Post-hydrothermal Treatment (PHT). For increasing the crystallinity of ZnO nanoparticles, PHT was carried out with a pressure variation of 1 and 3 bar. The resulting nanoparticles were further characterized with X-Ray Diffraction (XRD), Ultra-Violet Visible (UV-Vis) spectroscopy and a Scanning Electron Microscope (SEM). The study showed that by increasing the PHT pressure from 1 to 3 bar caused an adverse effect on the crystallinity, i.e. the crystallite size of ZnO nanoparticles slightly decreased from 27.42 to 26.88 nm. This was expected to be due to the increase of the boiling point of water causing less effective of vapor generated to improve the crystallinity by a cleavage mechanism on the inorganic framework. The band gap energy (Eg), however, was found to increase slightly from 3.25 to 3.26 eV, respectively. Considering the obtained properties, ZnO nanoparticles in this study have the potential to be used as the semiconductor oxide layer in the dye-sensitized solar cells."

"Zinc oxide (ZnO) nanoparticles have been investigated in depth, due to their potential as a semiconductor material in dye sensitized solar cell applications. In this current research, ZnO nanostructure was synthesized using a simple precipitation technique with the addition of citric acid (C6H8O7)as the capping agent. Various ratios of ZnO and citric acid were prepared, i.e. 1:1, 2:1, 4:1 and calcination temperatures of 150 and 400°C were used to investigate the effect of those parameters on the ZnO nanostructure and its crystallinity. The nanostructure characteristics, i.e. nanocrystallite size, crystallinity, and optical properties were determined by using x-ray diffraction (XRD), scanning electron microscopy (SEM), and ultra-violet visible (UV-Vis) spectroscopy, respectively. The investigation results showed that ZnO nanostructure was formed as spherical shapes and rods in the range of 19.8–30.8 nm with the lowest band gap energy (Eg) of 3.15 eV obtained under conditions of a 4:1 ratio and calcined at 400°C. Considering nanostructural characteristics, the ZnO nanostructures in this study would be suitable for application as a semiconductor oxide layer in a dye sensitized solar cell."

"Dalam penelitian ini, nanopartikel ZnO telah berhasil disintesis melalui metode presipitasi sederhana, yang kemudian dilanjutkan dengan beberapa perlakuan termal, seperti pengeringan, kalsinasi, serta pasca-hidrotermal. Perlakuan pasca-hidrotermal dilakukan dengan variasi tekanan 1 dan 3 bar, yang secara khusus ditujukan untuk menginvestigasi pengaruh tekanan pada perlakuan pasca-hidrotermal terhadap peningkatan kristalinitas, pertumbuhan kristalit, dan penurunan energi celah pita nanopartikel ZnO. Hasil penelitian menunjukkan bahwa dengan meningkatkan tekanan perlakuan pasca-hidrotermal, peningkatan kristalinitas masih belum optimal. Hal ini dikarenakan oleh peningkatan titik didih air, menyebabkan uap air yang dihasilkan kurang optimal dalam meningkatkan kristalinitas. Hasil penelitian juga menunjukkan penurunan ukuran kristalit dari hasil perlakuan pasca-hidrotermal 1 dan 3 bar, yaitu 27.42 dan 26.88 nm, masing-masing, sedangkan energi celah pita menunjukkan peningkatan, yaitu 3.25 dan 3.26 eV, masing-masing. Nanopartikel ZnO dalam penelitian ini memiliki potensi untuk digunakan sebagai lapisan semikonduktor oksida pada sel surya tersensitasi zat pewarna.

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In this study, ZnO nanoparticles have been successfully synthesized through simple precipitation method, which was then followed by thermal treatment, such as drying, calcination, and post-hydrothermal. Post-hydrothermal treatment was carried out with a pressure variation of 1 and 3 bar, which is specifically aimed at investigating the effect of pressure in post-hydrothermal treatment on the crystallinity enhancement, crystallite growth, and band gap energy reduction of ZnO nanoparticles. The study shows that with increasing the pressure of post-hydrothermal treatment from 1 to 3 bar, the crystallinity enhancement has not yet affect the properties of the resulting ZnO nanoparticles. This is due to the increase of water’s boiling point, causing less effective vapor generated to improve the crystallinity. The study also shows a decrease in crystallite size of the post-hydrothermal treatment result at 1 and 3 bar, which are 27.42 and 26.88 nm, respectively, while the band gap energy shows an increase, which are 3.25 and 3.26 eV, respectively. ZnO nanoparticles in this study has the potential to be used as the oxide semiconductor layer in dye-sensitized solar cells."

"Among semiconductors, zinc oxide (ZnO) has received great attention due to its wide band-gap and high electron mobility, resulting in various strategic applications. Controlling the physical properties of ZnO is therefore a critical issue in the fabrication of related electronic and optical devices. In this study, ZnO nanorods layers were grown on an ITO glass substrate via chemical bath deposition at low temperature. Prior to the growing process, the layers were deposited using a spin-coating technique. The seeding solution was made by dissolving zinc nitrate tetrahydrate and hexamethylene tetraamine in cold water (0oC) for an hour using a cooler bath. The as-synthesized ZnOs were further subjected to different post-hydrothermal treatment series at a temperature of 150oC for three hours at atmospheric pressure and at 100°C for one hour under one bar of nitrogen gas (N2) pressure. The characterization was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and UV-Vis spectroscopy. The SEM results showed that the ZnO nanorods were grown as a vertically aligned hexagonal structure, while the XRD patterns showed a high intensity at the (002) plane. On the basis of investigation, it was found that under post-hydrothermal treatment at 150oC for three hours with atmospheric pressure, the synthesis procedure resulted in nanostructures in the form of ZnO rods. Meanwhile, post-hydrothermal treatment at 100°C for one hour under one bar of nitrogen gas (N2) produced ZnO rods and tubes. In general, the post-hydrothermal process provided a high degree of crystallinity. The optimum ZnO layer was obtained after post-hydrothermal treatment at 150oC for three hours at atmospheric pressure, with a crystallite size and band-gap energy of ~18 nm and 3.20 eV, respectively."

"Nanopartikel oksida logam merupakan salah satu jenis material yang kini banyak dikembangkan karena sifatnya yang baik sebagai konduktor, sensor serta dalam reaksi fotokatalisis. Nanopartikel ZnO, yang merupakan material semikonduktor dengan energi celah pita yang lebar, diuji aktivitas fotokatalitiknya dibawah radiasi sinar UV dan sinar tampak. Dikarenakan energi celah pitanya yang lebar, aktivitas fotokatalitik ZnO di bawah radiasi sinar tampak menjadi cukup rendah. Nanopartikel ZnO, dalam penelitian ini, dimodifikasi menggunakan nanopartikel MnO2 untuk menurunkan energi celah pita sehingga aktivitas fotokatalitiknya meningkat.Dalam penelitian ini, sintesis nanopartikel ZnO-MnO2 dilakukan melalui metode green synthesis dengan bantuan ekstrak tali putri sebagai sumber alkaloid dan capping agent. Uji aktivitas fotokatalitik nanopartikel ZnO, MnO2, dan ZnO-MnO2 dilakukan dengan mereaksikannya dengan rhodamin B, pewarna organik yang bersifat karsinogenik, di bawah radiasi sinar tampak dan sinar UV. Melalui penelitian ini didapatkan bahwa persen degradasi rhodamin B oleh nanopartikel ZnO, MnO2, dan ZnO-MnO2 adalah 60.21, 29.10, dan 93.41 di bawah radiasi sinar UV sedangkan di bawah sinar tampak 34.66 oleh ZnO, 15.852 oleh MnO2 dan 55.85 oleh ZnO-MnO2.

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Metal oxide nanoparticle is one of the material that is continously being researched for its conductivity, sensitivity as a sensor, and photocalytic ability. In this research, ZnO nanoparticle, which is a semiconductor material that has wide bandgap, is studied for its photocatalytic activity under irradiation of UV and visible light. Since ZnO nanoparticle has wide bandgap, its photocatalytic activity is quite poor under visible light irradiation. In this research, ZnO nanoparticle is modified by MnO2 to decrease its bandgap so the photocatalytic activity will increase in return. This ZnO MnO2 nanopartcile is synthesized using Cassytha filiformis extract, making this as a green synthesis method.

The photocatalytic activity of ZnO, MnO2, and ZnO MnO2 nanoparticle is studied with rhodamine B, a carsinogenic organic dye, as the model. In this research, it is obtained that the percentage of degradation of rhodamine B using ZnO, MnO2, and ZnO MnO2 nanoparticle is 60.21, 29.10, and 93.41 under irradiation of UV light, meanwhile under irradiation of visible light, ZnO reached 34.66, MnO2 reached 15.852, and ZnO MnO2 55.85."

"Nanostructured zinc oxide (ZnO) was synthesized via a sonochemical method. The effect of the duration of ultrasonic irradiation in a continuous mode on the generated particles was investigated. Additionally, the effect of flowing either air or nitrogen during the sonication process was investigated. Zinc nitrate and ammonia water-based solutions were selected as chemicals without the addition of other surfactants. The generated particles indicated that a wurtzite structure of ZnO in a hexagonal phase was formed with a crystalline size that increased as the ultrasound irradiation time increased. The morphology of the generated ZnO particles could be changed from flowerlike to needlelike structures via continuous ultrasound irradiation over one to two hours, resulting in increases in the particle lengths and decreases in the particle diameters from 200 to 80 nm. Photoluminescence intensity was also increased with increases in the ultrasonic irradiation times. Photoluminescence spectra were also influenced by the atmospheric environment. Two bands centered at 390 and 500 nm were generated under a nitrogen environment. On the other hand, a single wide band with a peak at around 430 nm was found for particles generated under an air environment. It can be applied for light emitting diodes (LED) or laser fabrication with a controlled emitting band."

"Zinc Oxide ZnO merupakah salah satu bahan semikonduktor yang banyak diteliti sebagai fotokatalis, namun salah satu kelemahan ZnO adalah rekombinasi yang cepat antara elektron dengan hole yang mengakibatkan efisiensi aktifitas fotokatalitik rendah. Salah satu upaya untuk menekan rekombinasi ini adalah dengan membuat struktur komposit ZnO dengan nanopartikel logam mulia Au dan Ag yang dapat menangkap elektron. Pada penelitian ini dilakukan sintesis nanopartikel AuAg pada nanorod ZnO yang ditumbuhkan di atas kaca dengan metode one-pot hydrothermal. Rasio mol prekursor Au:Ag 1:0 ; 3:1 ; 1:1 ; 1:3 dan 0:1.Hasil FESEM dan TEM menunjukkan bahwa umumnya nanopartikel Au terbentuk dengan diameter 15-30 nm cukup banyak di permukaan nanorod ZnO. Dengan penambahan unsur Ag terlihat jumlah nanopartikel yang terbentuk lebih sedikit dan ukurannya menjadi lebih beragam bahkan terjadi aglomerasi. Nanopartikel AuAg yang terbentuk memiliki struktur kristal fcc dengan bidang dominan 111.

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Zinc Oxide ZnO is one of the most studied semiconductor materials as a photocatalyst, but one of the weaknesses of ZnO is rapid recombination between electrons and holes resulting in low photocatalytic activity efficiency. One attempt to suppress this recombination is to create a ZnO composite structure with noble metal nanoparticles Au and Ag that can capture electrons. In this study, the synthesis of AuAg nanoparticles on ZnO nanorods was grown on glass by one pot hydrothermal method. The mole ratio of Au precursors Ag 1 0 3 1 1 1 1 3 and 0 1.

FESEM and TEM results show that generally Au nanoparticles are formed with a diameter of 15 30 nm in large number on the surface of ZnO nanorods. With the addition of Ag elements it is seen that the number of nanoparticles formed is less and the size becomes more diverse and even the agglomeration occurs. The AuAg nanoparticles formed have an face center cubic crystal structure with a dominant 111 crystal plane."

"Sampel La0,67Sr0,33Mn1-xFexO3 dengan x = 0 ; 0.05 ; 0.10 ; 0.15 dan 0.50 dari bahan dasar La2O3, SrCO2, MnCO3, dan Fe2O3 disentesis dengan menggunakan metode mechanical alloying. Keempat bahan dasar tersebut dicampur dengan menggunakan Planetary Ball Milling selama 15 jam, dikompaksi, kalsinasi pada suhu 800°C selama 8 jam dan disintering pada suhu 1200°C selama 12 jam. Identifikasi fasa dilakukan dengan menggunakan difraksi sinar X dan refinement GSAS dan diperoleh sampel La0,67Sr0,33Mn1-xFexO3 single phase untuk semua komposisi x, yang memiliki struktur kristal Rhombohedral. Pengukuran terhadap nilai konduktivitas dan magnetoresistansi (MR) sampel diukur menggunakan Four Point Probe (FPP), sedangkan nilai magnetisasinya diukur menggunakan permagraph. Berdasarkan hasil pengukuran tersebut disimpulkan bahwa semakin besar doping Fe yang diberikan pada sampel La0,67Sr0,33Mn1-xFexO3 membuat nilai magnetisasi dan konduktivitas sampel semakin menurun. Nilai negatif magnetoresistansi sampel pada umumnya mengalami penurunan. Untuk x = 0.05 nilai negatif magnetoresistansi sampel paling besar yaitu 3,65%, tetapi untuk x = 0.5 bersifat positif magnetoresistansi. Penurunan nilai magnetisasi dan konduktivitas sampel terjadi karena adanya kompetisi interaksi Double Exchange (DE) dan superexchange yang terjadi pada sistem. Interaksi Double Exchange (DE) terjadi antara ion Mn3+-O-Mn4+, sedangkan interaksi superexchange muncul karena interaksi antara ion Fe3+-O-Fe3+ akibat adanya doping Fe pada site Mn di sistem sampel La0,67Sr0,33Mn1-xFexO3.

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La0,67Sr0,33Mn1-xFexO3 sample with concentration x = 0 ; 0.05 ; 0.10 ; 0.15 ; and 0,5 of La2O3, SrCO2, MnCO3, and Fe2O3 are synthesized using mechanical alloying. The fourth of basic matter are mixed with using Planetary Ball Milling during 15 hours, compacted, calcinations on 8000C during 8 hours and sinter at 1200°C during 12 hours. Phase identification is carried out using X ray diffraction and GSAS refinement, getting La0,67Sr0,33Mn1-xFexO3 which single phase for all x composition, that have Rhombohedral crystal structure. Conductivity and magnetoresistance (MR) are measured using Four Point Probe (FPP), while magnetization is measured using permagraph. From the measurement we get that the bigger Fe doping the more magnetization and conductivity is decreases. For negative magnetoresistance generally is decreases, the biggest negative magnetoresistance is 3,65% for x = 0.05, but for x = 0.5 has positive magnetoresistance. The decreases of magnetization and conductivity due to there were competition between Double Exchange (DE) and Superexchange in the system. Double Exchange (DE) interaction happened between Mn3+-O-Mn4+ ion, while Superexchange a rises because of interaction between Fe3+-O-Fe3+ ion due to Fe doping on Mn site in the La0,67Sr0,33Mn1-xFexO3."

"ZnO merupakan salah satu semikonduktor yang menarik untuk dikembangkan sebagai fotokatalis untuk mengolah zat pewarna tekstil menjadi produk yang kurang berbahaya. Pada penelitian ini disintesis ZnO nanorod diatas substrat kaca dengan metode Ultrasonic Spray Pyrolysis dan hydrothermal. Untuk meningkatkan aktivitas fotokatalitiknya, nanorod ZnO diberi doping unsur Mn dengan lima konsentrasi yang berbeda 0, 1, 3, 5 dan 7 mol. Hasil karakterisasi dengan menggunakan FESEM, XRD, XPS, Spektroskopi Raman, Spektrofotometer UV-Vis dan Photoluminescence menunjukan bahwa penambahan unsur Mn dapat memperbesar luas permukaan nanorod ZnO, meningkatkan kristalinitas dan cacat kristal khususnya kekosongan O. Hal ini menyebabkan aktifitas fotokatalitiknya dapat meningkat. Penambahan unsur Mn 7 menghasilkan degradasi metil biru tertinggi yaitu 76,75 dalam waktu 38 menit.

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ZnO is one of the interesting semiconductors to be developed as a photocatalyst to process the textile dyes into less harmful products. In this study, ZnO nanorod was synthesized on glass substrate by ultrasonic spray pyrolysis and hydrothermal methods. In order to improve the photocatalytic activity, ZnO nanorods were doped with Mn element with 5 different concentrations 0, 1, 3, 5 and 7 mol.

The characterization results using FESEM, XRD, XPS, Raman Spectroscopy, UV Vis Spectrophotometer and Photoluminescence show that the addition of Mn element can increase the surface area of ZnO nanorod, crystallinity and crystal defect especially vacancy O. This causes the photocatalytic activity was increased. The addition of Mn 7 element resulted in the highest methyl blue degradation of 76.75 within 38 minutes."

"Tesis ini membahas tentang fabrikasi dan pengujian sel surya berbasis sintesa larutan (DSSC) dengan bahan utama ZnO sebagai elektroda dan struktur tandem sebagai struktur utamanya. Bahan ZnO digunakan karena mudah didapatkan dan sifat fisisnya serta energinya memiliki kemiripan dengan bahan bandgap lebar yang sudah lebih dulu digunakan, seperti TiO2, dengan mobilitas elektron yang lebih tinggi. Penulis telah berhasil membuat sampel DSSC berbahan ZnO dengan struktur tandem. Berdasarkan pengujian, tampak bahwa struktur tandem memiliki potensi untuk meningkatkan tegangan keluaran hingga 90%, namun salah satu kendala yang terjadi adalah menjaga kestabilan nilai arus kedua tumpukan DSSC agar nilai arus keluaran struktur tandem tidak mengalami penurunan.

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This tesis describes about fabrication and measurement of DSSC with ZnO as main cathode material and tandem as main structure. ZnO is used because it is easy to be found and its physical and energy characteristics are similar to TiO2 with higher electron mobility. ZnO-based DSSC with tandem structure sample has been made. From the test, it can be seen that tandem structure is able to increase output voltage up to 90%, but one of threat that need to be concerned is the stability of current value for each single DSSC, so that the output current of tandem DSSC won’t be decreased."