Usta, Hakan
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HAKAN USTA
Usta, H.
Usta, Hakan
Usta, H.
Usta, Hakan
Job Title
Prof. Dr.
Email Address
hakan.usta@agu.edu.tr
Main Affiliation
02.07. Malzeme Bilimi ve Nanoteknoloji Mühendisliği
Status
Current Staff
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ORCID ID
Scopus Author ID
Turkish CoHE Profile ID
Google Scholar ID
WoS Researcher ID
Sustainable Development Goals
7
AFFORDABLE AND CLEAN ENERGY
2
Research Products
9
INDUSTRY, INNOVATION AND INFRASTRUCTURE
0
Research Products
Documents
81
Citations
5982
h-index
34
Documents
83
Citations
5775
Scholarly Output
69
Articles
46
Views / Downloads
2402/682
Supervised MSc Theses
2
Supervised PhD Theses
4
WoS Citation Count
1774
Scopus Citation Count
1852
WoS h-index
23
Scopus h-index
24
Patents
0
Projects
2
WoS Citations per Publication
25.71
Scopus Citations per Publication
26.84
Open Access Source
21
Supervised Theses
6
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| Journal | Count |
|---|---|
| Journal of Materials Chemistry C | 8 |
| ACS Applied Materials & Interfaces | 6 |
| Chemistry of Materials | 3 |
| Synthetic Metals | 3 |
| Nature Communications | 2 |
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Scholarly Output Search Results
Now showing 1 - 10 of 69
Article Citation - WoS: 13Citation - Scopus: 12Organic and Inorganic Semiconducting Materials-Based SERS: Recent Developments and Future Prospects(Royal Soc Chemistry, 2024) Ozdemir, Resul; Ozkan Hukum, Kubra; Usta, Hakan; Demirel, GokhanSurface-enhanced Raman spectroscopy (SERS) with high sensitivity/selectivity is a powerful analytical tool and has been widely used, particularly in the fields of chemistry, spectroscopy, molecular detection, food safety, anti-counterfeiting, and environmental monitoring. Conventional SERS detection relies on plasmonic materials (e.g., Au and Ag nanostructures) with exceedingly high enhancement factors up to 1012. However, these substrates encounter significant limitations, including poor reproducibility, high cost, lack of selectivity, limited SERS active area leading to inconsistent field enhancement and SERS signals, and the possibility of the photothermal decomposition of the analyte species. These drawbacks have the potential to impede detection accuracy and hinder large-scale practical applications. This review focuses on alternative approaches based on noble metal-free SERS substrates. Considering recent advancements in the field of SERS active platforms, we first introduce the implementation of inorganic compounds, including metal oxides, transition metal sulfides/-selenides/-tellurides, 2-D layered transition metal carbides and nitrides (Mxenes), metal-organic frameworks (MOFs), and single elemental inorganic materials for Raman signal enhancement applications. In the second part of the review, we highlight the fast-growing field of SERS-active organic platforms. Moreover, we discuss the promises and challenges for the future direction of organic and inorganic material-based SERS. Surface-enhanced Raman spectroscopy (SERS) is a powerful analytical tool and has been widely used, in different fields including molecular detection, food safety, anti-counterfeiting, and environmental monitoring.Article Citation - WoS: 20Citation - Scopus: 20Frequency and Electric Field Controllable Photodevice: FYTRONIX Device(Elsevier Science Bv, 2017) Tataroglu, A.; Al-Sehemi, Abdullah G.; Ozdemir, Mehmet; Ozdemir, Resul; Usta, Hakan; Al-Ghamdi, Ahmed A.; Yakuphanoglu, F.Al/p-Si/BODIPY/Al diode was fabricated by forming BODIPY organic layer on p-Si having ohmic contact. The electrical and photoresponse properties of the prepared diode were investigated in detail. The current-voltage ( I-V) measurements were performed under dark and various illumination intensities. It is observed that the photocurrent under illumination is higher than the dark current. The transient measurements indicate that the device exhibits both photodiode and photocapacitor behavior. We called this device as FYTRONIX device. The photoresponse behavior of the FYTRONIX device is controlled simultaneously by frequency and electric field. The FYRONIX device can be used as a photoresponse sensor in optoelectronic applications.Article Citation - WoS: 74Citation - Scopus: 76From 2-Methylimidazole to 1,2,3-Triazole: A Topological Transformation of ZIF-8 and ZIF-67 by Post-Synthetic Modification(Royal Soc Chemistry, 2017) Erkartal, Mustafa; Erkilic, Ufuk; Tam, Benjamin; Usta, Hakan; Yazaydin, Ozgur; Hupp, Joseph T.; Sen, UnalBridging ligand replacement in zeolitic imidazolate frameworks, ZIF-8 and ZIF-67, by 1,2,3-triazole was investigated. A complete substitution of 2-methylimidazole by 1,2,3-triazole resulted in a topological transformation of the parent framework from a sodalite (SOD) network to a diamond (DIA) network.Article Citation - WoS: 23Citation - Scopus: 27Revisiting the Role of Charge Transfer in the Emission Properties of Carborane-Fluorophore Systems: A TDDFT Investigation(Amer Chemical Soc, 2022) Tahaoglu, Duygu; Usta, Hakan; Alkan, FahriIn this study, we performed a detailed investigation of the S-1 potential energy surface (PES) of o-carborane-anthracene (o-CB-Ant) with respect to the C-C bond length on o-CB and the dihedral angle between o-CB and Ant moieties. The effects of different substituents (F, Cl, CN, and OH) on carbon- or boron-substituted o-CB, along with a pi-extended acene-based fluorophore, pentacene, on the nature and energetics of S-1 -> S-0 transitions are evaluated. Our results show the presence of a non-emissive S-1 state with an almost pure charge transfer (CT) character for all systems as a result of significant C-C bond elongation (C-C = 2.50-2.56 angstrom) on o-CB. In the case of unsubstituted o-CB-Ant, the adiabatic energy of this CT state corresponds to the global minimum on the S-1 PES, which suggests that the CT state could be involved in emission quenching. Despite large deformations on the o-CB geometry, predicted energy barriers are quite reasonable (0.3-0.4 eV), and the C-C bond elongation can even occur without a noticeable energy penalty for certain conformations. With substitution, it is shown that the dark CT state becomes even more energetically favorable when the substituent shows -M effects (e.g., -CN), whereas substituents showing +M effects (e.g., -OH) can result in an energy increase for the CT state, especially for partially stretched C-C bond lengths. It is also shown that the relative energy of the CT state on the PES depends strongly on the LUMO level of the fluorophore as this state is found to be energetically less favorable compared to other conformations when anthracene is replaced with pi-extended pentacene. To our knowledge, this study shows a unique example of a detailed theoretical analysis on the PES of the S-1 state in o-CB-fluorophore systems with respect to substituents or fluorophore energy levels. Our findings could guide future experimental work in emissive o-CB-fluorophore systems and their sensing/optoelectronic applications.Article Citation - WoS: 40Citation - Scopus: 40Design, Synthesis, and Characterization of Α,ω-Disubstituted Indeno[1,2-B]Fluorene Molecular Semiconductors. Enhancement of Ambipolar Charge Transport Through Synthetic Tailoring of Alkyl Substituents(Royal Soc Chemistry, 2016) Ozdemir, Mehmet; Choi, Donghee; Kwon, Guhyun; Zorlu, Yunus; Kim, Hyekyoung; Kim, Myung-Gil; Usta, HakanA series of indeno[1,2-b]fluorene-6,12-dione-thiophene derivatives with hydrocarbon substituents at alpha,omega-positions as side groups have been designed and synthesized. The new compounds were fully characterized by H-1/C-13 NMR, mass spectrometry, cyclic voltammetry, UV-vis absorption spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and melting point measurements. The solid state structure of the indeno[1,2-b]fluorene-6,12-dione acceptor core has been identified based on single-crystal X-ray diffraction (XRD). The structural and electronic properties were also studied using density functional theory calculations, which were found to be in excellent agreement with the experimental findings and provided further insight. The detailed effects of alkyl chain size and orientation on the optoelectronic properties, intermolecular cohesive forces, thin-film microstructures, and charge transport performance of the new semiconductors were investigated. Two of the new solution-processable semiconductors, 2EH-TIFDKT and 2OD-TIFDKT, were deposited as thin-films via solution-shearing, drop-casting, and droplet-pinned crystallization methods, and their morphologies and microstructures were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The solution-processed thin-film transistors based on 2EH-TIFDKT and 2OD-TIFDKT showed ambipolar device operations with electron and hole mobilities as high as 0.12 cm(2) V-1 s(-1) and 0.02 cm(2) V-1 s(-1), respectively, with Ion/Ioff ratios of 105 to 106. Here, we demonstrate that rational repositioning of the b-substituents to molecular termini greatly benefits the p-core planarity while maintaining a good solubility, and results in favorable structural and optoelectronic characteristics for more efficient charge-transport in the solid-state. The ambipolar charge carrier mobilities were increased by two-three orders of magnitude in the new indeno[1,2-b]fluorene-6,12-dione-thiophene core on account of the rational side-chain engineering.Article Citation - WoS: 11Citation - Scopus: 10Trans-Cis Isomerization Assisted Synthesis of Solution-Processable Yellow Fluorescent Maleic Anhydrides for White-Light Generation(Elsevier Science SA, 2015) Ozdemir, Mehmet; Genc, Sinan; Ozdemir, Resul; Altintas, Yemliha; Citir, Murat; Sen, Unal; Usta, HakanHeterocyclic maleic anhydride derivatives have been extensively studied in natural products chemistry over the past few decades. However, their incorporation into optoelectronic devices has lagged behind that of other pi-conjugated systems, and they have never been studied in white light emitting diodes (WLEDs). The development of emissive pi-conjugated materials for (WLEDs) has been an emerging scientific and technological research area to replace phosphors used in LED-based solid-state lighting. Here, we demonstrate the design, synthesis and characterization of two new highly emissive alkyl-substituted bis(thienyl)maleic anhydrides (C6-Th2MA and C12-Th2MA) with favorable photophysical properties. The new core is synthesized via a novel trans-to-cis isomerization-assisted one-pot reaction, which is demonstrated for the first time in the literature for the synthesis of a bis(heteroaryl)maleic anhydride. Due to its favorable absorption and fluorescence properties in the blue and yellow region of the visible spectrum, respectively, C12-Th2MA is studied as a potential wavelength-upconverting material. A WLED fabricated by drop-casting a polymeric solution of C12-Th2MA on a blue LED (InGaN, 455 nm) yields promising CIE coordinates and color-rendering index (CRI) values of (0.24, 0.20) and 65.0, respectively. Considering the simplicity of the current molecular structure and facile synthesis, alkyl-substituted bis(thienyl)maleic anhydrides stand as ideal phosphor alternatives. Therefore, the current findings may open new perspectives for the development of maleic anhydride-based small molecules for low-cost, energy-efficient, and solution-processed lighting technologies. (C) 2015 Elsevier B.V. All rights reserved.Master Thesis Solüsyondan Proses Edilebilir Çubuk Yapısında Moleküler Yarı İletkenler ve Alan Etkili Transistör Uygulamaları(Abdullah Gül Üniversitesi, 2018) DENEME, İBRAHİM; Deneme, İbrahim; Usta, HakanYeni n-tipi yarı iletkenlerin yapısal dizaynı ve sentetik olarak geliştirilmesi yük taşıma mekanizmasının temellerinin anlaşılması noktasında bilimsel ve teknolojik alanlarda önemli derecede ilgi uyandırmıştır. Son yıllarda literatürde mevcut çok sayıda n-tipi yarı iletken olmasına rağmen, solüsyondan proses edilebilen ve havada kararlı n-tipi yarı-iletken malzeme sayısı oldukça sınırlıdır. Burada biz, indeno[1,2-b]floren ve (triizopropilsilil)etinil tabanlı, 6,12-pozisyonlarında disiyanovinilen ve 2,8-pozisyonlarında ise karbonil fonksiyonel grupları içeren iki yeni moleküler yarı-iletkenlerin dizaynı, sentezi, tek kristal yapıları, optoelektronik özellikleri, çözelti ile proses edilmiş ince-film morfolojilerini/mikroyapılarını ve organik alan etkili transistör uygulamalarını ortaya koyduk. Elektron çekici karbonil, disiyanovinilen ve (triizopropilsilil)etinil gruplarının indeno[1,2-b]floren π-merkezine dahil edilmesi, tamamen akseptör tipinde π-konjuge yapının oluşmasına sebep olmaktadır. Söz konusu yeni moleküller, 2,8- (triizopropilsilil)etinil-indeno[1,2-b]floren-6,12-dion (TIPS-IFDK) ve 2,8-(triizopropilsilil)etinil-indeno[1,2-b]floren-6,12-bis(disiyanoviinilen) (TIPS-IFDM)'dir. Yeni bileşiklerin HOMO/LUMO enerjileri sırasıyla TIPS-IFDK için -5.77 / -3.65 eV ve TIPS-IFDM için -5.84 / -4.18 eV'dir. Daha önce geliştirilen donör-akseptör tipi indenofluorenler ile kıyaslandığında tamamen akseptör yapıda π-konjuge sisteme sahip oldukları için yeni moleküllerin optik bant aralıklarında artış gözlemlenmiştir. (TIPS-IFDK için 2.12 eV ve TIPS-IFDM için 1.66 eV) TIPS-IFDK ve TIPS-IFDM yarı-iletkenlerinin katı-hal düzenlemeleri ve moleküller arası π-π etkileşimleri, tek kristal X-ray difraksiyon (XRD) analizi ile incelenmiştir. Söz konusu yarı-iletkenler katı halde 1-D kolon yapısı ortaya koymuştur. Bu tez kapsamında geliştirilen TIPS-IFDM yarı-iletkeni kullanılarak, solüsyon-makaslama (solution-shearing) yöntemi ile alt kapı/üst temas organik alan etkili transistörler üretilmiştir. Havada son derece kararlı olan söz konusu transistörler n-tipi yük taşıma karakterinde olup, 0.02 cm2/Vs elektron hareketliliği, 107 Ion/Ioff oranı sergilemiştir. Buna rağmen bu tez kapsamında geliştirilen diğer molekül TIPS-IFDK, TIPS-IFDM ile kıyaslandığında 103 kat daha az elektron hareketliliği ortaya koymuştur. Bu durum TIPS-IFDK molekülünün zayıf π-π etkileşimleri ve ince-film fazında zayıf kristal yapısından kaynaklanmaktadır. Dolayısıyla TIPS-IFDK tabanlı OFET'ler havada kararlı değildir. (trialkilsilil)etinil grubunun HOMO/LUMO orbitalleri üzerindeki elektronik etkileri DFT hesaplamaları ile ortaya çıkarıldı. Bildiğimiz kadarıyla, TIPS-IFDM, uzun moleküler eksen (x) boyunca (trialkilsilil) etinil gruplarıyla fonksiyonel hale getirilmiş, çözücüde proses edilebilen, havada kararlı, n-tipi moleküler yarı iletkenlerin ilk örneğidir. Elde ettiğimiz sonuçlar, havada kararlı n-tipi organik alan etkili transistörler ve çeşitli organik optoelektronik teknoloji uygulamaları için kolay sentezlenebilir, solüsyondan proses edilebilir yeni molekülerin nasıl dizayn edileceği noktasında önemli bilgiler vermektedir. Bu alanlarda ilerde yapılacak araştırmalara ışık tutmaktadır.Article Citation - WoS: 104Citation - Scopus: 108Proton Conducting Poly(Vinyl Alcohol) (PVA)/Poly (2-Acrylamido Sulfonic Acid) (PAMPS)/Zeolitic Imidazolate Framework (ZIF) Ternary Composite Membrane(Elsevier, 2016) Erkartal, Mustafa; Usta, Hakan; Citir, Murat; Sen, UnalThe design, synthesis and characterization of novel proton exchange membranes (PEMs) are of significant scientific and technological importance for the realization of fuel cells, actuators, and sensors. Here, we demonstrate a novel ternary composite membrane consisting of poly(vinyl alcohol) (PVA), poly (2-acrylamido-2-methylpropane sulfonic acid) (PAMPS), zeolitic imidazolate framework-8 (ZIF-8), which is prepared by physical blending and casting methods. To enhance the water management of the membranes, in situ chemical cross-linking is carried out by glutaraldehyde (GA). During the characterization of the new membranes, FT-IR is used for intermolecular and inter-polymer interactions between different components of the membrane, SEM is used to identify morphology, XRD is used to prove the presence of ZIF-8 nanoparticles, and finally TGA is used for thermal stability. The proton conductivity of the membranes is found to increase with temperature and also with the increasing content of PAMPS. The highest proton conductivity under fully hydrated state at 80 degrees C is measured as 0.134 S cm(-1) for PVA: PAMPS: ZIF-8 (55:40:5) composition. In this study, it is clearly shown that ZIF-8 nanoparticles contribute to the proton conductivity by forming hydrogen bonds with the polymer network in the membrane. The water uptake (WU) and ion exchange capacity (IEC) values are 3.28 (gig) and 1.52 meq g(-1), respectively for the same membrane. To the best our knowledge, this study shows one of the first example of a MOFcontaining membrane with truly high proton conductivities, and both values of proton conductivity and electrochemical properties are comparable to those of well-studied membrane, Nation. (C) 2015 Elsevier B.V. All rights reserved.Article Citation - WoS: 28Citation - Scopus: 29A Solution-Processable Liquid-Crystalline Semiconductor for Low-Temperature Air-Stable N-Channel Field-Effect Transistors(Wiley-VCH Verlag GmbH, 2017) Ozdemir, Resul; Choi, Donghee; Ozdemir, Mehmet; Kim, Hyekyoung; Kostakoglu, Sinem Tuncel; Erkartal, Mustafa; Usta, HakanA new solution-processable and air-stable liquid-crystalline nchannel organic semiconductor (2,2'-(2,8-bis(5-(2-octyldodecyl) thiophen-2-yl) indeno[1,2-b] fluorene-6,12-diylidene) dimalononitrile, alpha,omega-2OD-TIFDMT) with donor-acceptor-donor (D-AD) pi conjugation has been designed, synthesized, and fully characterized. The new semiconductor exhibits a low LUMO energy (-4.19 eV) and a narrow optical bandgap (1.35 eV). The typical pseudo-focal-conic fan-shaped texture of a hexagonal columnar liquid-crystalline (LC) phase was observed over a wide temperature range. The spin-coated semiconductor thin films show the formation of large (approximate to 0.5-1 mu m) and highly crystalline platelike grains with edge-on molecular orientations. Low-temperature-annealed (50 degrees C) top-contact/bottom-gate OFETs have provided good electron obility values as high as 0.11 cm(2) (Vs)(-1) and high I-on/I-off ratios of 10(7) to 10(8) with excellent ambient stability. This indicates an enhancement of two orders of magnitude (100 V) when compared with the b-substituted parent semiconductor, beta-DD-TIFDMT (2,2'-(2,8-bis(3-dodecylthiophen- 2-yl) indeno[1,2-b] fluorene-6,12-diylidene) dimalononitrile). The current rational alkyl-chain engineering route offers great advantages for D-A-D pi-core coplanarity in addition to maintaining good solubility in organic solvents, and leads to favorable optoelectronic/physicochemical characteristics. These remarkable findings demonstrate that alpha,omega-2OD-TIFDMT is a promising semiconductor material for the development of n-channel OFETs on flexible plastic substrates and LC-state annealing of the columnar liquid crystals can lower the electron mobility for transistor-type charge transport.Book Part Citation - Scopus: 2Paper-Based Substrates for Sustainable (OPTO)Electronic Devices(Elsevier, 2022) Usta, Hakan; Facchetti, A. F.Cellulose-based paper has been a convenient eco-friendly platform for storing and exchanging information for thousands of years. Amazingly, the studies and advancements in the past decade have demonstrated that paper and nanocellulose-based substrates are also attractive for fabricating flexible electronic circuits as well as optoelectronic components and devices. Paper and nanocellulose-based substrates have been considered for use in new generation green devices and optoelectronic applications based on their sustainable and inexpensive source, lightweight, and superior mechanical/optical properties, all factors that could also reduce manufacturing costs for producing these devices. In this chapter, we review functional materials and optoelectronic devices fabricated on paper or nanocellulose-based substrates including transistors and circuits, solar cells, light-emitting diodes, and other devices, such as sensors/actuators, batteries, supercapacitors/energy-harvesters, and breathalyzer/diagnosis devices. We also thoroughly discuss remaining challenges and promising research directions with paper-based substrates for future advancements in green optoelectronics. © 2022 Elsevier B.V., All rights reserved.
