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1.
Baohua Wang;Wei Hui;Qiangqiang Zhao;Yuezhou Zhang;Xinxin Kang;Maoxin Li;Lei Gu;Yaqi Bao;Jiacheng Su;Jie Zhang;Xingyu Gao;Shuping Pang;Lin Song; 《Small (Weinheim an der Bergstrasse, Germany)》2024,20(35):2310455
Organometal halide perovskite solar cells (PSCs) have received great attention owing to a rapid increase in power conversion efficiency (PCE) over the last decade. However, the deficit of long-term stability is a major obstacle to the implementation of PSCs in commercialization. The defects in perovskite films are considered as one of the primary causes. To address this issue, isocyanic acid (HNCO) is introduced as an additive into the perovskite film, in which the added molecules form covalent bonds with FA cations via a chemical reaction. This chemical reaction gives rise to an efficient passivation on the perovskite film, resulting in an improved film quality, a suppressed non-radiation recombination, a facilitated carrier transport, and optimization of energy band levels. As a result, the HNCO-based PSCs achieve a high PCE of 24.41% with excellent storage stability both in an inert atmosphere and in air. Different from conventional passivation methods based on coordination effects, this work presents an alternative chemical reaction for defect passivation, which opens an avenue toward defect-mitigated PSCs showing enhanced performance and stability. 相似文献
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《Journal of Experimental Nanoscience》2013,8(6):641-651
While the effect of electrochemical doping on single-layer graphene (SG) with holes and electrons has been investigated, the effect of charge-transfer doping on SG has not been examined hitherto. Effects of varying the concentration of electron donor and acceptor molecules such as tetrathiafulvalene (TTF) and tetracyanoethylene (TCNE) on SG produced by mechanical exfoliation as well as by the reduction of single-layer graphene oxide have been investigated. TTF softens the G-band in the Raman spectrum, whereas TCNE stiffens the G-band. The full-width-at-half-maximum of the G-band increases on interaction with both TTF and TCNE. These effects are similar to those found with few-layer graphene, but in contrast to those found with electrochemical doping. A common feature between the two types of doping is found in the case of the 2-D band, which shows softening and stiffening on electron and hole doping, respectively. The experimental results are explained on the basis of the frequency shifts, electron–phonon coupling and structural inhomogeneities that are relevant to molecule–graphene interaction. 相似文献
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Pawan Kumar Jayeeta Biswas Juhi Pandey Kartikey Thakar Ajay Soni Saurabh Lodha Viswanath Balakrishnan 《Advanced Materials Interfaces》2019,6(20)
Stabilizing defective domains of sub‐monolayer thickness in 2D materials plays a significant role in tuning the electronic and optical properties. The chemical vapor deposition growth of WS2 monolayers with control over phase and uniformly nucleated defect domains is reported. Multifold photoluminescence (PL) enhancement (≈20‐fold) is achieved by stabilizing defect‐dominated domains toward design of nanoscale optical devices. While the observed luminescence variation in the form of alternating triangles arises from planar heterostructure (1H–1T′) formation, defect domain present at the center of WS2 heterophase monolayer causes 20‐fold enhancement in photoluminescence. The observed luminescence enhancement is correlated with sulfur defects and confirmed by site‐specific spatial X‐ray photoemission spectroscopy and in situ PL measurements at cryogenic temperatures. Detailed microstructural and spectroscopic observations indicate the partial stripping of monolayers by removal of sulfur and incorporation of oxygen leading to increased excitonic emissions. The demonstrated atomic‐scale manipulation to stabilize defect domains over large area with enhanced luminescence behavior is relevant for developing next‐generation nanoscale photonic devices. 相似文献
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Jiaqi Li;Xinxiang Wu;Caifeng Jian;Xianyan Qiao;Fang Wan;Zhenguo Wu;Benhe Zhong;Yanxiao Chen;Xiaodong Guo; 《Small (Weinheim an der Bergstrasse, Germany)》2024,20(17):2307912
Lithium–sulfur batteries with high capacity are considered the most promising candidates for next-generation energy storage systems. Mitigating the shuttle reaction and promoting catalytic conversion within the battery are major challenges in the development of high-performance lithium-sulfur batteries. To solve these problems, a novel composite material GO-CoNiP is synthesized in this study. The material has excellent conductivity and abundant active sites to adsorb polysulfides and improve reaction kinetics within the battery. The initial capacity of the GO-CoNiP separator battery at 1 C is 889.4 mAh g−1, and the single-cycle decay is 0.063% after 1000 cycles. In the 4 C high-rate test, the single-cycle decay is only 0.068% after 400 cycles. The initial capacity is as high as 828.2 mAh g−1 under high sulfur loading (7.3 mg cm−2). In addition, high and low-temperature performance tests are performed on the GO-CoNiP separator battery. The first cycle discharge reaches 810.9 mAh g−1 at a low temperature of 0 °C, and the first cycle discharge reaches 1064.8 mAh g−1 at a high temperature of 60 °C, and both can run stably for 120 cycles. In addition, in situ Raman tests are conducted to explain the adsorption of polysulfides by GO-CoNiP from a deeper level. 相似文献
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Balakrishna Ananthoju Ravi K. Biroju Wolfgang Theis Robert A. W. Dryfe 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(48)
A reliable method to prepare a surface‐enhanced Raman scattering (SERS) active substrate is developed herein, by electrodeposition of gold nanoparticles (Au NPs) on defect‐engineered, large area chemical vapour deposition graphene (GR). A plasma treatment strategy is used in order to engineer the structural defects on the basal plane of large area single‐layer graphene. This defect‐engineered Au functionalized GR, offers reproducible SERS signals over the large area GR surface. The Raman data, along with X‐ray photoelectron spectroscopy and analysis of the water contact angle are used to rationalize the functionalization of the graphene layer. It is found that Au NPs functionalization of the “defect‐engineered” graphene substrates permits detection of concentrations as low as 10?16 m for the probe molecule Rhodamine B, which offers an outstanding molecular sensing ability. Interestingly, a Raman signal enhancement of up to ≈108 is achieved. Moreover, it is observed that GR effectively quenches the fluorescence background from the Au NPs and molecules due to the strong resonance energy transfer between Au NPs and GR. The results presented offer significant direction for the design and fabrication of ultra‐sensitive SERS platforms, and also open up possibilities for novel applications of defect engineered graphene in biosensors, catalysis, and optoelectronic devices. 相似文献
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《Small Methods》2017,1(6)
Quantitative surface‐enhanced Raman spectroscopy (SERS) with ultrahigh sensitivity will significantly promote its practical application in many fields, such as environment monitoring, food safety, and drug detection. However, the challenges that remain unresolved, particularly in the low concentration levels, arise from the instability of the SERS spectra and the uncertainty of the number of detected molecules. Herein, a graphene‐based, flexible, and transparent substrate for SERS quantification is reported, wherein the 2D single‐crystalline nature of graphene promises the homogeneous adsorption of molecules, facilitating the determination of the number of molecules, the separation of molecules from metal, which ensures the stability of the Raman signals, and an internal standard for the calibration of SERS intensities. The in situ quantification of probe molecules is demonstrated in an aqueous solution down to the detection limit of 10−8m , and the real‐time, in situ monitoring of the release process of rhodamine B molecules, which mimics practical application, for example, the controlled release of medicine, is shown. The results open up an avenue for reliable SERS quantification for practical applications with high efficiency and low cost. 相似文献
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Eli Janzen Hannah Schutte Juliette Plo Adrien Rousseau Thierry Michel Wilfried Desrat Pierre Valvin Vincent Jacques Guillaume Cassabois Bernard Gil James H. Edgar 《Advanced materials (Deerfield Beach, Fla.)》2024,36(2):2306033
The unique physical, mechanical, chemical, optical, and electronic properties of hexagonal boron nitride (hBN) make it a promising 2D material for electronic, optoelectronic, nanophotonic, and quantum devices. Here, the changes in hBN's properties induced by isotopic purification in both boron and nitrogen are reported. Previous studies on isotopically pure hBN have focused on purifying the boron isotope concentration in hBN from its natural concentration (≈20 at% 10B, 80 at% 11B) while using naturally abundant nitrogen (99.6 at% 14N, 0.4 at% 15N), that is, almost pure 14N. In this study, the class of isotopically purified hBN crystals to 15N is extended. Crystals in the four configurations, namely h10B14N, h11B14N, h10B15N, and h11B15N, are grown by the metal flux method using boron and nitrogen single isotope (> 99%) enriched sources, with nickel plus chromium as the solvent. In-depth Raman and photoluminescence spectroscopies demonstrate the high quality of the monoisotopic hBN crystals with vibrational and optical properties of the 15N-purified crystals at the state-of-the-art of currently available 14N-purified hBN. The growth of high-quality h10B14N, h11B14N, h10B15N, and h11B15N opens exciting perspectives for thermal conductivity control in heat management, as well as for advanced functionalities in quantum technologies. 相似文献
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Liu Qian Yilin Sun Mingmao Wu Dan Xie Liming Ding Gaoquan Shi 《Advanced materials (Deerfield Beach, Fla.)》2017,29(22)
Phototransistors with a structure of a nitrogen‐doped graphene quantum dots (NGQDs)–perovskite composite layer and a mildly reduced graphene oxide (mrGO) layer are fabricated through a solution‐processing method. This hybrid phototransistor exhibits broad detection range (from 365 to 940 nm), high photoresponsivity (1.92 × 104 A W?1), and rapid response to light on–off (≈10 ms). NGQDs offer an effective and fast path for electron transfer from the perovskite to the mrGO, resulting in the improvement of photocurrent and photoswitching characteristics. The high photoresponsivity can also be ascribed to a photogating effect in the device. In addition, the phototransistor shows good stability with poly(methyl methacrylate) encapsulation, and can maintain 85% of its initial performance for 20 d in ambient air. 相似文献
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Xiang Li Yu Qiao Shaohua Guo Zhenming Xu Hong Zhu Xiaoyu Zhang Yang Yuan Ping He Masayoshi Ishida Haoshen Zhou 《Advanced materials (Deerfield Beach, Fla.)》2018,30(14)
Conventional cathodes of Li‐ion batteries mainly operate through an insertion–extraction process involving transition metal redox. These cathodes will not be able to meet the increasing requirements until lithium‐rich layered oxides emerge with beyond‐capacity performance. Nevertheless, in‐depth understanding of the evolution of crystal and excess capacity delivered by Li‐rich layered oxides is insufficient. Herein, various in situ technologies such as X‐ray diffraction and Raman spectroscopy are employed for a typical material Li1.2Ni0.2Mn0.6O2, directly visualizing O?? O? (peroxo oxygen dimers) bonding mostly along the c‐axis and demonstrating the reversible O2?/O? redox process. Additionally, the formation of the peroxo O? O bond is calculated via density functional theory, and the corresponding O? O bond length of ≈1.3 Å matches well with the in situ Raman results. These findings enrich the oxygen chemistry in layered oxides and open opportunities to design high‐performance positive electrodes for lithium‐ion batteries. 相似文献
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Rahul R. Nair Wencai Ren Rashid Jalil Ibtsam Riaz Vasyl G. Kravets Liam Britnell Peter Blake Fredrik Schedin Alexander S. Mayorov Shengjun Yuan Mikhail I. Katsnelson Hui‐Ming Cheng Wlodek Strupinski Lyubov G. Bulusheva Alexander V. Okotrub Irina V. Grigorieva Alexander N. Grigorenko Kostya S. Novoselov Andre K. Geim 《Small (Weinheim an der Bergstrasse, Germany)》2010,6(24):2773-2773
A stoichiometric derivative of graphene with a fluorine atom attached to each carbon is reported. Raman, optical, structural, micromechanical, and transport studies show that the material is qualitatively different from the known graphene‐based nonstoichiometric derivatives. Fluorographene is a high‐quality insulator (resistivity >1012 Ω) with an optical gap of 3 eV. It inherits the mechanical strength of graphene, exhibiting a Young’s modulus of 100 N m?1 and sustaining strains of 15%. Fluorographene is inert and stable up to 400 °C even in air, similar to Teflon. 相似文献
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Nair RR Ren W Jalil R Riaz I Kravets VG Britnell L Blake P Schedin F Mayorov AS Yuan S Katsnelson MI Cheng HM Strupinski W Bulusheva LG Okotrub AV Grigorieva IV Grigorenko AN Novoselov KS Geim AK 《Small (Weinheim an der Bergstrasse, Germany)》2010,6(24):2877-2884
A stoichiometric derivative of graphene with a fluorine atom attached to each carbon is reported. Raman, optical, structural, micromechanical, and transport studies show that the material is qualitatively different from the known graphene-based nonstoichiometric derivatives. Fluorographene is a high-quality insulator (resistivity >10(12) Ω) with an optical gap of 3 eV. It inherits the mechanical strength of graphene, exhibiting a Young's modulus of 100 N m(-1) and sustaining strains of 15%. Fluorographene is inert and stable up to 400 °C even in air, similar to Teflon. 相似文献
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S. P. Lebedev D. G. Amel’chuk I. A. Eliseyev I. S. Barash P. A. Dementev A. V. Zubov 《Fullerenes, Nanotubes and Carbon Nanostructures》2020,28(4):281-285
AbstractThe dependence of surface morphology of the SiC(0001) substrate on the rate with which it is heated up to the temperature of graphene growth was studied by three techniques: atomic force microscopy, Raman spectroscopy and Kelvin probe force microscopy. The study was carried out for the rates of substrates heating ranging from 100?°C/min to 320?°C/min. As a result, it was found out that both the width of the terraces forming on the surface of SiC substrate and the uniformity of the graphene layers covering these terraces significantly depend on the applied rate of the heating. It was also shown that the most homogeneous monolayer graphene with the minimum of double-layers inclusions is formed if the rate of SiC heating is about 250?°C/min. 相似文献
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Jones JD Shah RK Verbeck GF Perez JM 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(7):1066-1072
The removal of single atomic layers from multi-layer graphene using a He plasma is reported. By applying sample biases of -60 and +60 V during He plasma exposure, layer removal is found to be due to electrons instead of He ions or neutrals in the plasma. The rate of layer removal depends on exposure time, sample bias, and pre-annealing treatments. Optical contrast microscopy and atomic force microscopy studies show that the removal of C atoms occurs approximately one layer at a time across the entire multi-layer sample with no observable production of large pits or reduction in lateral dimensions. Layer removal is proposed to arise from the electron-stimulated dissociation of C atoms from the basal plane. This process differs from plasma techniques that use reactive species to etch multi-layer graphene. 相似文献