Ultrasonication-assisted synthesis of CsPbBr₃ and Cs₄PbBr₆ perovskite nanocrystals and their reversible transformation

• Longshi Rao,
• Xinrui Ding,
• Xuewei Du,
• Guanwei Liang,
• Yong Tang,
• Kairui Tang and
• Jin Z. Zhang

Beilstein J. Nanotechnol. 2019, 10, 666–676, doi:10.3762/bjnano.10.66

• defects or from impurities or from a combination of both [37][38]. Herein, the purified Cs4PbBr6 PNCs did not demonstrate PL emission over the whole visible spectrum due to their wide bandgap (Eg(Cs4PbBr6) = 3.94 eV), while the observed weak PL emission results from a small portion of CsPbBr3 impurities

Direct observation of the CVD growth of monolayer MoS₂ using in situ optical spectroscopy

• Claudia Beatriz López-Posadas,
• Yaxu Wei,
• Wanfu Shen,
• Daniel Kahr,
• Michael Hohage and
• Lidong Sun

Beilstein J. Nanotechnol. 2019, 10, 557–564, doi:10.3762/bjnano.10.57

• , the DT signal at a higher energy of 3.2 eV begins to dominate. Based on its energy position, this feature can be attributed to the absorption of MoO3 [32][33]. As a semiconductor, MoO3 shows a bandgap around 3 eV. Considering the high temperature of the substrate, we can exclude the possibility that

Temperature-dependent Raman spectroscopy and sensor applications of PtSe₂ nanosheets synthesized by wet chemistry

• Mahendra S. Pawar and
• Dattatray J. Late

Beilstein J. Nanotechnol. 2019, 10, 467–474, doi:10.3762/bjnano.10.46

• semimetallic nature and single-layer PtSe2 has a semiconducting nature with a bandgap of 1.2 eV. Bilayer PtSe2 is also a semiconducting material but with a slightly smaller band gap than the monolayer material [19]. This layer-dependent conversion of semimetal-to-semiconductor transition has potential for

Reduced graphene oxide supported C₃N₄ nanoflakes and quantum dots as metal-free catalysts for visible light assisted CO₂ reduction

• Md Rakibuddin and
• Haekyoung Kim

Beilstein J. Nanotechnol. 2019, 10, 448–458, doi:10.3762/bjnano.10.44

• of photo-induced electron–hole pairs and insufficient adsorption of CO2 at the catalyst surface are crucial problems preventing effective catalyst performance and CO2 reduction [11]. An ideal photocatalyst for CO2 conversion should possess a narrow bandgap and good light-harvesting properties, proper

Geometrical optimisation of core–shell nanowire arrays for enhanced absorption in thin crystalline silicon heterojunction solar cells

• Robin Vismara,
• Olindo Isabella,
• Andrea Ingenito,
• Fai Tong Si and
• Miro Zeman

Beilstein J. Nanotechnol. 2019, 10, 322–331, doi:10.3762/bjnano.10.31

• reflected by the top surface of the nanowire, thus increasing total reflection. Anttu et al. suggest another possible explanation for the optimal cross section value [19]. In their work on III–V semiconductors nanowire arrays, they observed the presence of optimum, bandgap-dependent nanowire diameter values

Raman study of flash-lamp annealed aqueous Cu₂ZnSnS₄ nanocrystals

• Yevhenii Havryliuk,
• Oleksandr Selyshchev,
• Mykhailo Valakh,
• Alexandra Raevskaya,
• Oleksandr Stroyuk,
• Constance Schmidt,
• Volodymyr Dzhagan and
• Dietrich R. T. Zahn

Beilstein J. Nanotechnol. 2019, 10, 222–227, doi:10.3762/bjnano.10.20

• sulfide Cu2ZnSnS4 (CZTS); CuS; Cu-Sn-S; kesterite; phonon; pulsed light crystallization; Raman spectroscopy; secondary phase; SnS; Introduction Affordable and non-toxic solar energy materials having a high absorption coefficient and a bandgap in the solar illumination range are an ever-growing research

Surface plasmon resonance enhancement of photoluminescence intensity and bioimaging application of gold nanorod@CdSe/ZnS quantum dots

• Siyi Hu,
• Yu Ren,
• Yue Wang,
• Jinhua Li,
• Junle Qu,
• Liwei Liu,
• Hanbin Ma and
• Yuguo Tang

Beilstein J. Nanotechnol. 2019, 10, 22–31, doi:10.3762/bjnano.10.3

• emission. This greater lifetime resulted from the trapping states caused by surface defects located within the bandgap, which led to a rise of nonradioactive recombination. When the GNRs were doped with CdSe/ZnS QDs, more radiative and nonradioactive processes occurred at the particle surface, which

Zn/F-doped tin oxide nanoparticles synthesized by laser pyrolysis: structural and optical properties

• Florian Dumitrache,
• Iuliana P. Morjan,
• Elena Dutu,
• Ion Morjan,
• Claudiu Teodor Fleaca,
• Monica Scarisoreanu,
• Alina Ilie,
• Marius Dumitru,
• Cristian Mihailescu,
• Adriana Smarandache and
• Gabriel Prodan

Beilstein J. Nanotechnol. 2019, 10, 9–21, doi:10.3762/bjnano.10.2

• content and crystallite size. The fluorine presence is due to the catalytic partial decomposition of the SF6 laser energy transfer agent. In direct correlation with the increase in the Zn doping level, the bandgap of co-doped nanoparticles shifts to lower energy (from 3.55 to 2.88 eV for the highest Zn

• dopant concentration). Keywords: laser pyrolysis; nanoparticles; optical bandgap; Zn/F-doped SnO2; Introduction Recently, there has been growing interest in the field of transparent conducting oxides and wide bandgap oxide nanocrystalline materials such as tin oxide (SnO2). It is generally agreed that

• SnO2 in its undoped form is an n-type semiconductor with a direct bandgap of 3.6 eV at room temperature. Its n-type conductivity is due to oxygen vacancies in its rutile structure. The bandgap, starting from the bulk value, increases as the size of the nanocrystal decreases, due to electron confinement

Graphene-enhanced metal oxide gas sensors at room temperature: a review

• Dongjin Sun,
• Yifan Luo,
• Marc Debliquy and
• Chao Zhang

Beilstein J. Nanotechnol. 2018, 9, 2832–2844, doi:10.3762/bjnano.9.264

• change in graphene resistance via altering the local carrier concentration. After that, a wave of research regarding graphene has been set off. The mass production of single-layered graphene is difficult. Another problem is that pristine graphene does not have a bandgap, which means it is not suitable

• that the response can be significantly improved. ZnO is widely used as a typical wide-bandgap (3.37 eV) metal-oxide gas sensor material. However, the problem with ZnO gas sensors is their poor selectivity [66]. Li et al. [67] synthesized urchin-like ZnO nanorods–graphene via a facile solvothermal

• dioxide (TiO2), as a wide-bandgap semiconductor, has been widely used as photocatalyst, and in solar cells and gas sensors [70][71][72]. In general, its operating temperature is over 200 °C, so scholars try to prepare composites with graphene to reduce its operating temperature. However, the stability of

Near-infrared light harvesting of upconverting NaYF₄:Yb³⁺/Er³⁺-based amorphous silicon solar cells investigated by an optical filter

• Daiming Liu,
• Qingkang Wang and
• Qing Wang

Beilstein J. Nanotechnol. 2018, 9, 2788–2793, doi:10.3762/bjnano.9.260

• cells, the hydrogenated amorphous silicon (a-Si:H) thin-film solar cell is one of the most promising candidates due to its high inherent absorption coefficient, short charge-carrier diffusion length and low production cost [1]. Films of a-Si:H with a wide bandgap of ca. 1.75 eV have a high absorption in

• energy loss can be substantially reduced through spectral upconversion (UC) [6]. Spectral UC describes nonlinear anti-Stokes optical processes that can convert two (or more) NIR photons to a visible photon. In terms of its application in solar cells, UC is expected to convert the sub-bandgap NIR light to

• above-bandgap visible light. The photons generated during upconversion are then absorbed by photoactive semiconductors to generate electron–hole pairs. This means that UC can broaden the absorption spectrum and enhance the photoelectric conversion efficiency of solar cells. Based on a detailed balance

Oriented zinc oxide nanorods: A novel saturable absorber for lasers in the near-infrared

• Pavel Loiko,
• Tanujjal Bora,
• Josep Maria Serres,
• Haohai Yu,
• Magdalena Aguiló,
• Francesc Díaz,
• Uwe Griebner,
• Valentin Petrov,
• Xavier Mateos and
• Joydeep Dutta

Beilstein J. Nanotechnol. 2018, 9, 2730–2740, doi:10.3762/bjnano.9.255

• nanorods; Q-switching; saturable absorption; solid-state lasers; zinc oxide; Introduction Zinc oxide (ZnO) is a well-known II–IV group wide-bandgap semiconductor (Eg = 3.37 eV), possessing a hexagonal wurtzite-type (sp. gr. P63mc) structure with unit cell parameters a = 3.25 Å, c = 5.20 Å. In recent years

• the singly (VO+1) and doubly charged (VO+2) oxygen vacancy states of ZnO, respectively [36][37][38]. Based on these assignments, a schematic diagram showing the position of the various defect states within the bandgap of ZnO and the corresponding PL lines is presented in Figure 3e. Absorption

• components; (e) scheme of the defect states in the bandgap of ZnO (the color of arrows corresponds to the color of the emission bands in (d). Absorption saturation of ZnO nanorods (NRs): (a,b) NRs grown for 10 h, (a) open-aperture Z-scan experiment and (b) the corresponding absorption saturation curve

Impact of the anodization time on the photocatalytic activity of TiO₂ nanotubes

• Jesús A. Díaz-Real,
• Geyla C. Dubed-Bandomo,
• Juan Galindo-de-la-Rosa,
• Luis G. Arriaga,
• Janet Ledesma-García and
• Nicolas Alonso-Vante

Beilstein J. Nanotechnol. 2018, 9, 2628–2643, doi:10.3762/bjnano.9.244

• length, fluorine content, and capacitance of the space charge region increased, affecting the opto-electronic properties (bandgap, bathochromic shift, band-edge position) and surface hydrophilicity of TiO2 NTs. These properties are at the origin of the photocatalytic activity (PCA), as proved with the

• ][41]. These observations are relevant to our study since the presence of both F and N signals suggests a co-doping effect, as shown in Figure S1a (Supporting Information File 1). Moreover, the modification of the bandgap can be ascribed to the doping effect and will be discussed in the following

• N and F. Nevertheless, some physical phenomena such as light scattering (from the top part of the TNTs) and oxygen vacancies could also create distortions in the IPCE spectra. Furthermore, the bandgap (Eg) can be obtained from the Tauc plots, Figure 7b, plotting jph as a function of the wavelength

Enhancement of X-ray emission from nanocolloidal gold suspensions under double-pulse excitation

• Wei-Hung Hsu,
• Frances Camille P. Masim,
• Armandas Balčytis,
• Hsin-Hui Huang,
• Tetsu Yonezawa,
• Aleksandr A. Kuchmizhak,
• Saulius Juodkazis and
• Koji Hatanaka

Beilstein J. Nanotechnol. 2018, 9, 2609–2617, doi:10.3762/bjnano.9.242

• speed of light in vacuum, A is the absorbance, εb is the binding energy [eV/atom], and Ji is the ionization potential. The threshold fluence for the creation of the ENZ state is calculated for full ionization, i.e., with the bandgap energy Δg in Equation 3 instead of (εb + Ji). For water, Δg = 9.5 eV

• of solvated electrons. When the bandgap energy of water Δg = 9.5 eV is taken as the ionization threshold, a slightly larger fluence of = 60 mJ/cm2 will result. For the metal (gold nanoparticles) we consider the ablation threshold expression equivalent to Equation 3 in which binding energy and

Thickness-dependent photoelectrochemical properties of a semitransparent Co₃O₄ photocathode

• Malkeshkumar Patel and
• Joondong Kim

Beilstein J. Nanotechnol. 2018, 9, 2432–2442, doi:10.3762/bjnano.9.228

• respect to the water redox potential [3][9][10]. The spinel Co3O4 is interesting because of its dual bandgap (1.5 and 2.2 eV), high absorption coefficient, intrinsic p-type doping and chemical stability. It has found application as a light-absorbing entity in all-metal-oxide photovoltaic cells [11][12][13

• ][14][15][16][17]. Dual-bandgap Co3O4 films provide distinct band states in the energy–momentum diagram, which is advantageous to reduce the thermalisation-related losses in the sunlight-driven hydrogen generation. Dual bandgaps in Co3O4 originate from the crystal-field split Co 3d states at the

Performance analysis of rigorous coupled-wave analysis and its integration in a coupled modeling approach for optical simulation of complete heterojunction silicon solar cells

• Ziga Lokar,
• Benjamin Lipovsek,
• Marko Topic and
• Janez Krc

Beilstein J. Nanotechnol. 2018, 9, 2315–2329, doi:10.3762/bjnano.9.216

• refraction). The latter is especially important in solar cells where indirect semiconductors such as silicon (Si) are used as an absorber layer, where the absorption coefficient at the photon energy approaching the value of energy bandgap is small. Furthermore, efficient light management is important in

Optimization of the optical coupling in nanowire-based integrated photonic platforms by FDTD simulation

• Nan Guan,
• Andrey Babichev,
• Martin Foldyna,
• Dmitry Denisov,
• François H. Julien and
• Maria Tchernycheva

Beilstein J. Nanotechnol. 2018, 9, 2248–2254, doi:10.3762/bjnano.9.209

• tunable bandgap [14] and reduced dislocation density [15][16], nitride nanowires (NWs) have become important materials for optical components in the visible to ultraviolet (UV) spectral range [17][18]. Despite their small size, single NW light emitting diodes (LEDs) can produce bright electroluminescence

Lead-free hybrid perovskites for photovoltaics

• Oleksandr Stroyuk

Beilstein J. Nanotechnol. 2018, 9, 2209–2235, doi:10.3762/bjnano.9.207

• market is dominated by silicon solar cells with top light-to-current conversion efficiencies reaching ≈27% [1]. As an alternative to the Si-based cells requiring a relatively thick absorber layer due to the indirect character of electron transitions in Si, direct-bandgap metal chalcogenide semiconductors

• + cations Hybrid perovskites with partially substituted lead ions Using a small “tool kit” of two metals, Sn and Pb, and two organic cations, A = MA and FA, a broad variety of isostructural Pb-, Sn- and Pb–Sn-based ASnxPb1−xI3 HPs can be synthesized with a bandgap varying from 1.25 to 1.75 eV depending on

• the HP composition [92]. By simultaneously tuning the composition of Pb–Sn and halide components, a solar light absorber was designed with a bandgap of 1.35 eV ideal for the solar light harvesting. The inverted cells based on MAPb0.5Sn0.5(I0.8Br0.2)3 demonstrated PCEs of up to 17.63% [70]. A

Spin-coated planar Sb₂S₃ hybrid solar cells approaching 5% efficiency

• Pascal Kaienburg,
• Benjamin Klingebiel and
• Thomas Kirchartz

Beilstein J. Nanotechnol. 2018, 9, 2114–2124, doi:10.3762/bjnano.9.200

• routes based on different precursors reported in the literature. By studying the film morphology, sub-bandgap absorption and solar cell performance, improved annealing procedures are found and the crystallization temperature is shown to be critical. In order to determine the optimized processing

• -bandgap region [53][54][55][56] including band tails that yield the Urbach energy as a measure of disorder as well as the detection of (optically active) defects in the band gap which can act as recombination centers in a solar cell. The Sb-TU process shows a slight increase in uncovered substrate area

• attributed to interference in the smooth films – which did not fully cancel out during data analysis – instead of actual variations in the materials’ density of states in the sub-bandgap region. The negative impact of the increased defect density on device performance is confirmed by comparing solar cells

Improving the catalytic activity for hydrogen evolution of monolayered SnSe_2(1−x)S_2x by mechanical strain

• Sha Dong and
• Zhiguo Wang

Beilstein J. Nanotechnol. 2018, 9, 1820–1827, doi:10.3762/bjnano.9.173

• ][33][34][35][36][37]. For example, Komsa et al. [34] have investigated the electronic properties of monolayer MoS2xSe2(1−x) and found that the bandgaps can be continuously tuned with the variation of Se composition. Liu et al. [38] have studied Mo1−xWxS2 and observed variations of the direct bandgap

• ] and agrees well with previous results [36]. SnS2 and SnSe2 monolayers are indirect-bandgap semiconductors, as highlighted in their band structures shown in Figure 1e and Figure 1i, respectively. The valence-band maximum (VBM) is located at the M-point, whereas the conduction-band minimum (CBM) is

• , Figure 1g and Figure 1h, respectively. The substitution of S with Se does not affect the indirect bandgap semiconducting characteristics; however, the band gap is tuned with changing the content of Se, as shown in Figure 1d with the indirect band gap decreasing with increasing Se content. These results

Multimodal noncontact atomic force microscopy and Kelvin probe force microscopy investigations of organolead tribromide perovskite single crystals

• Yann Almadori,
• David Moerman,
• Jaume Llacer Martinez,
• Philippe Leclère and
• Benjamin Grévin

Beilstein J. Nanotechnol. 2018, 9, 1695–1704, doi:10.3762/bjnano.9.161

• shifts are observed when the wavelength falls below the MAPbBr3 bandgap (EG ≈ 2.2eV [12]). This confirms that the measured height changes originate from the intrinsic photostriction of the MAPbBr3 crystal. However, an almost identical photoresponse is observed under 405 nm and 515 nm illumination, which

• seems different from the case of MAPbI3 (for which a wavelength-dependent photostriction was observed [16] above the bandgap). Here, it is noteworthy that the wavelength of our green laser falls within an absorption peak due to a strong excitonic transition [24][25]. Further measurements at intermediate

• wavelengths (currently unavailable in our setup) would be necessary to draw a definitive conclusion about the wavelength dependency of the photoresponse above the bandgap. The fast surface photovoltage polarity implies that negative charges accumulate quickly under illumination beneath the surface of the

Absence of free carriers in silicon nanocrystals grown from phosphorus- and boron-doped silicon-rich oxide and oxynitride

• Daniel Hiller,
• Julian López-Vidrier,
• Keita Nomoto,
• Michael Wahl,
• Wolfgang Bock,
• Tomáš Chlouba,
• František Trojánek,
• Sebastian Gutsch,
• Margit Zacharias,
• Dirk König,
• Petr Malý and
• Michael Kopnarski

Beilstein J. Nanotechnol. 2018, 9, 1501–1511, doi:10.3762/bjnano.9.141

• concentration of a semiconductor can be controlled via doping. Conventional impurity doping requires the incorporation of a suitable foreign atom on a lattice site and its ionization by thermal energy. Therefore, the energetic position of a dopant in the bandgap has to be close to the respective band edges. For

Cr(VI) remediation from aqueous environment through modified-TiO₂-mediated photocatalytic reduction

• Rashmi Acharya,
• Brundabana Naik and
• Kulamani Parida

Beilstein J. Nanotechnol. 2018, 9, 1448–1470, doi:10.3762/bjnano.9.137

Robust midgap states in band-inverted junctions under electric and magnetic fields

• Álvaro Díaz-Fernández,
• Natalia del Valle and
• Francisco Domínguez-Adame

Beilstein J. Nanotechnol. 2018, 9, 1405–1413, doi:10.3762/bjnano.9.133

• spinful two-band model that is equivalent to the Dirac model for relativistic electrons. The mass term is half the bandgap and changes its sign across the junction. For the sake of algebraic simplicity, we assumed same-sized and aligned gaps, although this is not a serious limitation to the validity of

Ag₂WO₄ nanorods decorated with AgI nanoparticles: Novel and efficient visible-light-driven photocatalysts for the degradation of water pollutants

• Shijie Li,
• Shiwei Hu,
• Wei Jiang,
• Yanping Liu,
• Yu Liu,
• Yingtang Zhou,
• Liuye Mo and
• Jianshe Liu

Beilstein J. Nanotechnol. 2018, 9, 1308–1316, doi:10.3762/bjnano.9.123

• photocatalytic performance for dye degradation under light irradiation [30][31][36][37]. Unfortunately, due to its wide bandgap of about 3.1 eV, Ag2WO4 has limited photocatalytic activity under sunlight, which severely limits its application and illustrates the urgency for optimization of Ag2WO4 to overcome

• these disadvantages [38][39][40][41][42]. The integration of VLD components with wide bandgap semiconductors having well-matched energy bands has provided a new opportunity for the development of VLD photocatalysts [12]. As a consequence, some Ag2WO4-based composites containing VLD components such as

Computational exploration of two-dimensional silicon diarsenide and germanium arsenide for photovoltaic applications

• Sri Kasi Matta,
• Chunmei Zhang,
• Yalong Jiao,
• Anthony O'Mullane and
• Aijun Du

Beilstein J. Nanotechnol. 2018, 9, 1247–1253, doi:10.3762/bjnano.9.116

• dynamic stability of the compounds, which is inferred by analyzing their vibrational normal mode. SiAs2 and GeAs2 monolayers possess a bandgap of 1.91 and 1.64 eV, respectively, which is excellent for sunlight harvesting, while the exciton binding energy is found to be 0.25 and 0.14 eV, respectively