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Inspired by the successful transfer of freestanding ultrathin films of SrTiO3 and BiFeO3 onto various substrates without any thickness limitation, in this study, using density functional theory (DFT), we assessed the structural stability of a group of two-dimensional perovskite-type materials which we call perovskenes. Specifically, we analyzed the stability of 2D SrTiO3, SrZrO3, BaTiO3, and BaZrO3 monolayers. Our simulations revealed that the 2D monolayers of SrTiO3, BaTiO3, and BaZrO3 are at least meta-stable, as confirmed by cohesive energy calculations, evaluation of elastic constants, and simulation of phonon dispersion modes. With this information, we proceeded to investigate the electronic, optical, and thermoelectric properties of these perovskenes. To gain insight into their promising applications, we investigated the electronic and optical properties of these 2D materials and found that they are wide bandgap semiconductors with significant absorption and reflection in the ultraviolet (UV) region of the electromagnetic field, suggesting them as promising materials for use in UV shielding applications. In addition, evaluating their thermoelectric factors revealed that these materials become better conductors of electricity and heat as the temperature rises. They can, hence, convert temperature gradients into electrical energy and transport electrical charges, which is beneficial for efficient power generation in thermoelectric devices. This work opens a new window for designing a novel family of 2D perovskite type materials termed perovskenes. The vast variety of different perovskite compounds and their variety of applications suggest deeper studies on the perovskenes materials for use in innovative technologies. Perovskenes: a novel family of high-stability two-dimensional perovskite-type monolayer materials with predicted electronic, optical, and thermoelectric properties predicted via first-principles calculations., National Research Council of Canada, Artificial Intelligence for Design program; Natural Sciences and Engineering Research Council of Canada, Discovery Grant [RGPIN-2019-03976]; Compute Canada (now the Digital Research Alliance of Canada); TUBITAK ULAKBIM, High Performance and Grid Computing Center, This work is supported by the National Research Council of Canada, Artificial Intelligence for Design program, by the Natural Sciences and Engineering Research Council of Canada, Discovery Grant (RGPIN-2019-03976) and by Compute Canada (now the Digital Research Alliance of Canada). The work is also supported by TUBITAK ULAKBIM, High Performance and Grid Computing Center (TR-Grid e-Infrastructure).

Inspired by the successful transfer of freestanding ultrathin films of SrTiO3 and BiFeO3 onto various substrates without any thickness limitation, in this study, using density functional theory (DFT), we assessed the structural stability of a group of two-dimensional perovskite-type materials which we call perovskenes. Specifically, we analyzed the stability of 2D SrTiO3, SrZrO3, BaTiO3, and BaZrO3 monolayers. Our simulations revealed that the 2D monolayers of SrTiO3, BaTiO3, and BaZrO3 are at least meta-stable, as confirmed by cohesive energy calculations, evaluation of elastic constants, and simulation of phonon dispersion modes. With this information, we proceeded to investigate the electronic, optical, and thermoelectric properties of these perovskenes. To gain insight into their promising applications, we investigated the electronic and optical properties of these 2D materials and found that they are wide bandgap semiconductors with significant absorption and reflection in the ultraviolet (UV) region of the electromagnetic field, suggesting them as promising materials for use in UV shielding applications. In addition, evaluating their thermoelectric factors revealed that these materials become better conductors of electricity and heat as the temperature rises. They can, hence, convert temperature gradients into electrical energy and transport electrical charges, which is beneficial for efficient power generation in thermoelectric devices. This work opens a new window for designing a novel family of 2D perovskite type materials termed perovskenes. The vast variety of different perovskite compounds and their variety of applications suggest deeper studies on the perovskenes materials for use in innovative technologies. Perovskenes: a novel family of high-stability two-dimensional perovskite-type monolayer materials with predicted electronic, optical, and thermoelectric properties predicted via first-principles calculations., National Research Council of Canada, Artificial Intelligence for Design program; Natural Sciences and Engineering Research Council of Canada, Discovery Grant [RGPIN-2019-03976]; Compute Canada (now the Digital Research Alliance of Canada); TUBITAK ULAKBIM, High Performance and Grid Computing Center, This work is supported by the National Research Council of Canada, Artificial Intelligence for Design program, by the Natural Sciences and Engineering Research Council of Canada, Discovery Grant (RGPIN-2019-03976) and by Compute Canada (now the Digital Research Alliance of Canada). The work is also supported by TUBITAK ULAKBIM, High Performance and Grid Computing Center (TR-Grid e-Infrastructure).

A pioneering CuBTABB-MOF/rGO composite customized electrode is fabricated and utilized as a sensor towards identifying bisphenol A (BPA) in a phosphate buffer solution of pH 7.0. The composite is characterized by FTIR, Raman spectroscopy, XRD, SEM, EDX, HRTEM, and XPS to study its structural and morphological properties. Compared with Cu-BTABB-MOF and Cu-BTABB-MOF@GO, the Cu-BTABB-MOF@rGO modified electrode is more sensitive and selective to BPA due to a strong interaction between them. The developed Cu-BTABB-MOF@rGO modified electrode exhibits good sensitivity (6.95 x 10(-5) A mol(-1) L-1) for BPA having a wide linear range of 0-100 mu mol L-1 with the LOD of 2.08 x 10(-5) mol L-1, reproducibility of 4.35%, and relative standard deviation (RSD) and stability of 90% for thirty days. In addition, the developed electrocatalyst remained unoccupied from interfering substances and consequently provided an encouraging platform for swift detection of BPA in real samples such as pond water and packed water bottles. Additionally, we utilized DFT (density functional theory) to model GO and Cu-BTABB-MOF structures for detecting BPA molecules., University Grants Commission-Government of India; SERB-CRG-India [CRG/2020/002163], The authors Srikanth Ponnada, Annapurna Nowduri, Demudu Babu Gorle, Maryam Sadat Kiai, and Chikkili Venkateswara Raju would like to acknowledge Andhra University College of Engineering-Visakhapatnam-India; Indian Institute of ScienceBangalore-India; Istanbul Technical University, IstanbulTurkey; IIT-Jodhpur, India, for resource and technical support of this work. Also, grateful to the University Grants Commission-Government of India for providing Dr D. S. Kothari Postdoctoral Fellowship.nancial support to DBG. Rakesh K. Sharma is grateful to SERB-CRG-India (CRG/2020/002163).

Low-symmetry penta-PdPSe (Pd4P4Se4) with intrinsic in-plane anisotropy was synthesized successfully [P. Li et al., Adv. Mater., 2021, 2102541]. Motivated by this experimental discovery, we investigate the structural, mechanical, electronic, optical and thermoelectric properties of PdPSe nanosheets via density functional theory calculations. The phonon dispersion, molecular dynamics simulation, and cohesive energy mechanical properties of the penta-PdPSe are verified to confirm its stability. The phonon spectrum represents a striking gap between the high-frequency and the low-frequency optical branches and an out-of-plane flexure mode with a quadratic dispersion in the long-wavelength limit. The Poisson's ratio indicates that penta-PdPSe is a brittle nanosheet. The penta-PdPSe is a semiconductor with an indirect bandgap of 1.40 (2.07) eV using the PBE functional (HSE06 hybrid functional). Optical properties simulation suggests that PdPSe is capable of absorbing a substantial range of visible to ultraviolet light. Band alignment analysis also reveals the compatibility of PdPSe for water splitting photocatalysis application. By combining the electrical and thermal transport properties of PdPSe, we show that a high power factor is achievable at room temperature, thus making PdPSe a candidate material for thermoelectric applications. Our findings reveal the strong potential of penta-PdPSe nanosheets for a wide array of applications, including optoelectronic, water splitting and thermoelectric device applications.

The atomic, electronic, optical, and mechanical properties of penta-like two-dimensional PdPX (X = O, S, Te) nanosheets have been systematically investigated using density functional theory calculations. All three PdPX nanosheets exhibit dynamic and mechanical stability on the basis of an analysis of phonon dispersions and the Born criteria, respectively. The PdPX monolayers are found to be brittle structures. Our calculations demonstrate that the PdPX nanosheets exhibit semiconducting characteristics with indirect band gaps of 0.93 (1.99), 1.34 (2.11), and 0.74 (1.51) eV for X = O, S, Te, respectively, using the PBE (HSE06) functional, where PdPTe is the best material for visible-light photocatalytic water splitting. Our findings give important basic characteristics of penta-like two-dimensional PdPX materials and should motivate further theoretical and experimental investigations of these interesting materials. ©

A pioneering CuBTABB-MOF/rGO composite customized electrode is fabricated and utilized as a sensor towards identifying bisphenol A (BPA) in a phosphate buffer solution of pH 7.0. The composite is characterized by FTIR, Raman spectroscopy, XRD, SEM, EDX, HRTEM, and XPS to study its structural and morphological properties. Compared with Cu-BTABB-MOF and Cu-BTABB-MOF@GO, the Cu-BTABB-MOF@rGO modified electrode is more sensitive and selective to BPA due to a strong interaction between them. The developed Cu-BTABB-MOF@rGO modified electrode exhibits good sensitivity (6.95 x 10(-5) A mol(-1) L-1) for BPA having a wide linear range of 0-100 mu mol L-1 with the LOD of 2.08 x 10(-5) mol L-1, reproducibility of 4.35%, and relative standard deviation (RSD) and stability of 90% for thirty days. In addition, the developed electrocatalyst remained unoccupied from interfering substances and consequently provided an encouraging platform for swift detection of BPA in real samples such as pond water and packed water bottles. Additionally, we utilized DFT (density functional theory) to model GO and Cu-BTABB-MOF structures for detecting BPA molecules., University Grants Commission-Government of India; SERB-CRG-India [CRG/2020/002163], The authors Srikanth Ponnada, Annapurna Nowduri, Demudu Babu Gorle, Maryam Sadat Kiai, and Chikkili Venkateswara Raju would like to acknowledge Andhra University College of Engineering-Visakhapatnam-India; Indian Institute of ScienceBangalore-India; Istanbul Technical University, IstanbulTurkey; IIT-Jodhpur, India, for resource and technical support of this work. Also, grateful to the University Grants Commission-Government of India for providing Dr D. S. Kothari Postdoctoral Fellowship.nancial support to DBG. Rakesh K. Sharma is grateful to SERB-CRG-India (CRG/2020/002163).

The atomic, electronic, optical, and mechanical properties of penta-like two-dimensional PdPX (X = O, S, Te) nanosheets have been systematically investigated using density functional theory calculations. All three PdPX nanosheets exhibit dynamic and mechanical stability on the basis of an analysis of phonon dispersions and the Born criteria, respectively. The PdPX monolayers are found to be brittle structures. Our calculations demonstrate that the PdPX nanosheets exhibit semiconducting characteristics with indirect band gaps of 0.93 (1.99), 1.34 (2.11), and 0.74 (1.51) eV for X = O, S, Te, respectively, using the PBE (HSE06) functional, where PdPTe is the best material for visible-light photocatalytic water splitting. Our findings give important basic characteristics of penta-like two-dimensional PdPX materials and should motivate further theoretical and experimental investigations of these interesting materials. ©

The reduction of dimensionality is a very effective way to achieve appealing properties in two-dimensional materials (2DMs). First-principles calculations can greatly facilitate the prediction of 2DM properties and find possible approaches to enhance their performance. We employed first-principles calculations to gain insight into the impact of different types of point defects (vacancies and substitutional dopants) on the electronic and magnetic properties of a ZnSnN2 (ZSN) monolayer. We show that Zn, Sn, and N + Zn vacancy-defected structures are p-type conducting, while the defected ZSN with a N vacancy is n-type conducting. For substitutional dopants, we found that all doped structures are thermally and energetically stable. The most stable structure is found to be B-doping at the Zn site. The highest work function value (5.0 eV) has been obtained for Be substitution at the Sn site. Li-doping (at the Zn site) and Be-doping (at the Sn site) are p-type conducting, while B-doping (at the Zn site) is n-type conducting. We found that the considered ZSN monolayer-based structures with point defects are magnetic, except those with the N vacancy defects and Be-doped structures. The ab initio molecular dynamics simulations confirm that all substitutionally doped and defected structures are thermally stable. Thus, our results highlight the possibility of tuning the magnetism in ZnSnN2 monolayers through defect engineering., National Research Foundation of Korea - Korean government (MSIT) [NRF-2015M2B2A4033123]; Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy within the Cluster of Excellence PhoenixDGerman Research Foundation (DFG) [EXC 2122, 390833453], This work was supported by the National Research Foundation of Korea Grant funded by the Korean government (MSIT) (NRF-2015M2B2A4033123). B.M. appreciates the funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy within the Cluster of Excellence PhoenixD (EXC 2122, Project ID 390833453).

The electronic and optical properties of vertical heterostructures (HTSs) and lateral heterojunctions (HTJs) between (B,N)-codoped graphene (dop@Gr) and graphene (Gr), C3N, BC3 and h-BN monolayers are investigated using van der Waals density functional theory calculations. We have found that all the considered HTSs are energetically and thermally feasible at room temperature, and therefore they can be synthesized experimentally. The dop@Gr/Gr, BC3/dop@Gr and BN/dop@Gr HTSs are semiconductors with direct bandgaps of 0.1 eV, 80 meV and 1.23 eV, respectively, while the C3N/dop@Gr is a metal because of the strong interaction between dop@Gr and C3N layers. On the other hand, the dop@Gr-Gr and BN-dop@Gr HTJs are semiconductors, whereas the C3N-dop@Gr and BC3-dop@Gr HTJs are metals. The proposed HTSs can enhance the absorption of light in the whole wavelength range as compared to Gr and BN monolayers. The applied electric field or pressure strain changes the bandgaps of the HTSs and HTJs, indicating that these HTSs are highly promising for application in nanoscale multifunctional devices., National Research Foundation of Korea (NRF) - Korean government (MSIT) [NRF-2015M2B2A4033123], This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (NRF-2015M2B2A4033123).

The electronic and optical properties of vertical heterostructures (HTSs) and lateral heterojunctions (HTJs) between (B,N)-codoped graphene (dop@Gr) and graphene (Gr), C3N, BC3 and h-BN monolayers are investigated using van der Waals density functional theory calculations. We have found that all the considered HTSs are energetically and thermally feasible at room temperature, and therefore they can be synthesized experimentally. The dop@Gr/Gr, BC3/dop@Gr and BN/dop@Gr HTSs are semiconductors with direct bandgaps of 0.1 eV, 80 meV and 1.23 eV, respectively, while the C3N/dop@Gr is a metal because of the strong interaction between dop@Gr and C3N layers. On the other hand, the dop@Gr-Gr and BN-dop@Gr HTJs are semiconductors, whereas the C3N-dop@Gr and BC3-dop@Gr HTJs are metals. The proposed HTSs can enhance the absorption of light in the whole wavelength range as compared to Gr and BN monolayers. The applied electric field or pressure strain changes the bandgaps of the HTSs and HTJs, indicating that these HTSs are highly promising for application in nanoscale multifunctional devices., National Research Foundation of Korea (NRF) - Korean government (MSIT) [NRF-2015M2B2A4033123], This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (NRF-2015M2B2A4033123).

Three-dimensional (3D) zinc oxide nanosheets (ZnO-NS), assembled on the FTO coated glass substrates after chemical treatment, have been achieved via a simple yet effective chemical bath deposition technique. The exploration of chalcogenide nanoparticle sensitization on ZnO-NS thin-film photoanodes led us to a spectacular enhancement in the photoelectrochemical conversion efficiency for solar-driven water splitting process as compared to the bare 3D-ZnO-NS. The maximum incident photon-to-charge carrier efficiency of bare 3D-ZnO-NS has been enhanced by approximately four folds as a result of cadmium sulfide (CdS) and cadmium selenide (CdSe) sensitization and the efficiency value have reached to 51% at 550 nm. Besides, the maximum charge injection and charge separation efficiencies of the ZnO eCdSe electrodes have been calculated as 93% and 64%, respectively. Numerical examination of the optical absorption and electrical field distribution has been performed via the finite-difference time-domain (FDTD) method in order to investigate the basis of the enhancement in the photoelectrochemical efficiencies of the 3D-ZnO-NS photoelectrodes. FDTD numerical simulation proved that the accumulation of rectangular 2D-nanosheets of ZnO in 3D-microspherical forms enhanced the light absorption significantly. Moreover, FDTD results also verified that the optical absorption of the ZnO electrodes has been extended from ultraviolet to visible region via CdS and CdSe nanoparticle deposition. (c) 2020 Elsevier B.V. All rights reserved.

Bu tezde, kimyasal banyo biriktirme (CBD) yöntemi kullanılarak flor katkılı kalay oksit (FTO) kaplı cam üzerine çiçek ve denizkestanesi benzeri üç boyutlu (3D) morfolojileri olan çinko oksit (ZnO) tabakaları büyütülmüştür. Daha sonra 3D-ZnO üzerine aynı yöntemle nanoyapılı kadmiyum sülfür (CdS) ve kadmiyum selenür (CdSe) tabakası büyütülmüştür. CdS ve CdSe kalkojen yapılara ek olarak, hazırlanan tezde ZnO nanoyapıların kurşun bromür perovskit (CsPbBr3) ile heteroeklemlerinin oluşturulması üzerine çalışılmıştır. Tüm bu heteroeklem yapılar, fotoelektrokimyasal güneş pillerinde fotoaktif elektrot olarak kullanılmıştır. Tez kapsamında CdSe ve CdS katmanlarını optimize etmek için ZnO / CdSe ve ZnO / CdS / CdSe yapısı 200 ° C'de 2 saat termal tavlama işlemine tabi tutularak performanslarının arttığı saptanmıştır. Üretilen tüm yapılar X-ışını fotoelektron spektroskopisi (XPS), x-ışını kırınım spektroskopisi (XRD), Uv-vis ve fotoluminesans (PL) spektroskopileri, kullanılarak analiz edilmiştir. Bunlara ek olarak üretilen morfolojiler ve kompozisyonları taramalı elektron mikroskopisi (SEM), geçirimli elektron mikroskopisi (TEM) ve enerji dağıtıcı X-ışını (EDX) ile analiz edilmiştir. İncefilmlerin başarı ile büyütüldüğü bu analizler sonucunda kanıtlanmış ve elde edilen buğuların literatüre paralel olduğu görülmüştür. Son olarak sentezlenen yapılar fotoelektrokimyasal güneş pili su ayırma sisteminde fotoanot olarak kullanılmıştır. Bu sistemin ana amacı güneş ışığını kullanarak suyun elektroliz edilmesi ve hidrojen üretilmesidir. Çıplak ZnO ve ZnO-CdS-CdSe elektrotlarının dış kuantum verimliliği (IPCE) sırasıyla %12 ve %51 olarak hesaplanmıştır. Ayrıca, ZnO-CsPbBr3 fotoelektrotların maksimum IPCE'si yaklaşık % 37 olduğu saptanmıştır. Bu veriler, çalışmamızda hazırlanan heteroeklem bazlı elektrotların, güneş enerjisi kullanılarak su ayrıştırılması sistemlerinde kullanmaları için çok ümit verici olduğunu göstermiştir., In this thesis, nanostructured zinc oxide (ZnO) layer with flower and urchin-like 3D morphologies have been deposited on fluorine-doped tin oxide (FTO) coated glass using chemical bath deposition (CBD) method. Then a thin layer of nanostructured cadmium sulfide (CdS) and selenide (CdSe) have been deposited on 3D ZnO with the same method. Additionally, a lead bromide perovskite (CsPbBr3) layer structure has been fabricated on the ZnO layer via spin coating method with the aim of the utilization of these material in to photoelectrochemical water splitting device as photo anode. Moreover, to modify the cadmium selenide layers, two ZnO/CdSe and ZnO/CdS/CdSe structures have been treated by thermal annealing at 200o C for 2 hours. As a result, the crystalline structure of the photoanodes was modified significantly. The structures also were analyzed using X-ray photoelectron spectroscopy (XPS), x-ray diffraction patters (XRD), Uv-vis and photoluminescence (PL) spectroscopies, finally the morphologies and compositions were analyzed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and energy dispersive X-ray (EDX). The substrates were proven by the mentioned analysis and compared with other works in literature. Then the synthesized structures were used as photoanode in the photoelectrochemical solar cell water splitting system. The aim of the system was the production of hydrogen from splitting water molecules using sunlight. The incident photon-to-charge carrier efficiency (IPCE) efficiency of the bare ZnO and ZnO-CdS-CdSe electrodes have been calculated as 12% and %51, respectively. Moreover, the maximum IPCE of the ZnO-CsPbBr3 photoelectrode was approximately 37%. These data indicated that the heterojunction based electrodes prepared in this study are very promising in order to utilize them into solar water splitting systems.