Green synthesis of fluorescent carbon dots from spices for in vitro imaging and tumour cell growth inhibition

• Nagamalai Vasimalai,
• Vânia Vilas-Boas,
• Juan Gallo,
• María de Fátima Cerqueira,
• Mario Menéndez-Miranda,
• José Manuel Costa-Fernández,
• Lorena Diéguez,
• Begoña Espiña and
• María Teresa Fernández-Argüelles

Beilstein J. Nanotechnol. 2018, 9, 530–544, doi:10.3762/bjnano.9.51

• attributed to surface state emission, intrinsic band emission, triple ground state emission, dipole emission involving electron–phonon coupling, transition from surface electrons to valence holes, self-trapped excitons and to the presence of small organic molecules. Moreover, the characteristic excitation

Dopant-stimulated growth of GaN nanotube-like nanostructures on Si(111) by molecular beam epitaxy

• Alexey D. Bolshakov,
• Alexey M. Mozharov,
• Georgiy A. Sapunov,
• Igor V. Shtrom,
• Nickolay V. Sibirev,
• Vladimir V. Fedorov,
• Evgeniy V. Ubyivovk,
• Maria Tchernycheva,
• George E. Cirlin and
• Ivan S. Mukhin

Beilstein J. Nanotechnol. 2018, 9, 146–154, doi:10.3762/bjnano.9.17

• high crystal quality of the synthesized GaN nanostructure arrays. It is well known that if the wave vector k of an incident wave is orthogonal to the c-axis of the NW crystal lattice, then three PL lines corresponding to free excitons of light XA, heavy XB and crystal field split XC holes are allowed

• as well as two PL lines corresponding to D0XA and D0XB excitons bound to neutral donors [36]. In our study we did not expect acceptor–bound excitons since the studied nanostructures were Si-doped. Figure 3 shows that four exciton lines of the PL spectra of our samples can be distinguished, namely: XA

• corresponding to the appearance of free XB excitons. The latter fact demonstrates that when the Si doping flux is lower than 1∙10−10 Torr (corresponding to a Si cell temperature lower than 1100 °C), the doping level is determined by the background doping. As can be seen in Figure 3, donor bound excitons are

Optical contrast and refractive index of natural van der Waals heterostructure nanosheets of franckeite

• Patricia Gant,
• Foad Ghasemi,
• David Maeso,
• Carmen Munuera,
• Elena López-Elvira,
• Riccardo Frisenda,
• David Pérez De Lara,
• Gabino Rubio-Bollinger,
• Mar Garcia-Hernandez and
• Andres Castellanos-Gomez

Beilstein J. Nanotechnol. 2017, 8, 2357–2362, doi:10.3762/bjnano.8.235

• generation of excitons [27]. In the case of franckeite we do not see any sharp resonance that could be attributed to exciton-generation processes within the explored range, as expected because the absorption band edge is far from the measurement window. Note that, to our knowledge, this information was not

Changes of the absorption cross section of Si nanocrystals with temperature and distance

• Michael Greben,
• Petro Khoroshyy,
• Sebastian Gutsch,
• Daniel Hiller,
• Margit Zacharias and
• Jan Valenta

Beilstein J. Nanotechnol. 2017, 8, 2315–2323, doi:10.3762/bjnano.8.231

• presence of one e–h pair does not influence the absorption of the second one (because of the relatively high [1] density of optical states (DOS) in Si NCs). According to the first assumption, and therefore relaxation of biexcitons in Equation 3 for a given fraction of excitons N1 (Equation 2) can be

Light-induced magnetoresistance in solution-processed planar hybrid devices measured under ambient conditions

• Sreetama Banerjee,
• Daniel Bülz,
• Danny Reuter,
• Karla Hiller,
• Dietrich R. T. Zahn and
• Georgeta Salvan

Beilstein J. Nanotechnol. 2017, 8, 1502–1507, doi:10.3762/bjnano.8.150

• thermally evaporated TIPS-pentacene OFETs in [9], which is an indication that the processing methods of the TIPS-pentacene do not influence the intrinsic mechanism of the OMAR in this organic semiconducting material. In the e–h model, the recombination into electrically neutral excitons and the dissociation

Spin-chemistry concepts for spintronics scientists

• Konstantin L. Ivanov,
• Alexander Wagenpfahl,
• Carsten Deibel and
• Jörg Matysik

Beilstein J. Nanotechnol. 2017, 8, 1427–1445, doi:10.3762/bjnano.8.143

• of OSCs are shown in Figure 1. Ideally, singlet excitons in either donor or acceptor material are generated upon light absorption (a), here shown as S0→S1 transition. For sake of simplicity we just consider the absorption taking place in the donor: the singlet exciton can diffuse towards the

• disorder [38]. Two optimization strategies for improving the power conversion efficiency based on spin processes are singlet fission and triplet–triplet annihilation (TTA). Singlet fission is the spin allowed conversion of one spin singlet exciton to two spin triplet excitons, which can occur with high

• Figure 1). A singlet exciton is photogenerated in the triplet sensitizer molecule and converted to a triplet by intersystem crossing (ISC). When two of such triplet excitons are transferred to the triplet acceptor, they can undergo TTA to generate a higher energy singlet exciton. The latter can be

Ultrasmall magnetic field-effect and sign reversal in transistors based on donor/acceptor systems

• Thomas Reichert and
• Tobat P. I. Saragi

Beilstein J. Nanotechnol. 2017, 8, 1104–1114, doi:10.3762/bjnano.8.112

• the quasi-particles can be bipolarons, excitons or electron hole pairs. USMFE could be detected in both unipolar and bipolar diodes and they represent a fundamental component of the MR line shape [24][25][26]. Herby, simple non-Lorentzian and Lorentzian functions are not suitable to fit MR line shapes

High photocatalytic activity of Fe₂O₃/TiO₂ nanocomposites prepared by photodeposition for degradation of 2,4-dichlorophenoxyacetic acid

• Shu Chin Lee,
• Hendrik O. Lintang and
• Leny Yuliati

Beilstein J. Nanotechnol. 2017, 8, 915–926, doi:10.3762/bjnano.8.93

• Figure 6. TiO2 exhibited three emission peaks at 407, 466 and 562 nm. The emission at 407 nm could be caused by the radiative recombination of self-trapped excitons, while peaks at 466 and 562 nm were attributed to the charge transfer of an oxygen vacancy trapped electron. The obtained results agreed

Tandem polymer solar cells: simulation and optimization through a multiscale scheme

• Fanan Wei,
• Ligang Yao,
• Fei Lan,
• Guangyong Li and
• Lianqing Liu

Beilstein J. Nanotechnol. 2017, 8, 123–133, doi:10.3762/bjnano.8.13

• simulation adopted here, please refer to [27]. Some of the parameters used in the MC simulation are presented in Table 1 (see below). where, nex_diss and nexciton are the number of dissociated excitons and the total number of generated excitons in the simulation, respectively. The recombination rates are

• excitons can only dissociate into electrons and holes at the interface between donor and acceptor, EDE is expected to decrease with domain size because the D/A interface area reduces as domain size increases. On the other hand, excitons are neutral and immune to the external and internal electric field

Effect of Anderson localization on light emission from gold nanoparticle aggregates

• Mohamed H. Abdellatif,
• Marco Salerno,
• Gaser N. Abdelrasoul,
• Ioannis Liakos,
• Alice Scarpellini,
• Sergio Marras and
• Alberto Diaspro

Beilstein J. Nanotechnol. 2016, 7, 2013–2022, doi:10.3762/bjnano.7.192

• constant of the medium. Keywords: Anderson localization; gold nanoparticle aggregates; photoluminescence; plasmons; surface plasmon resonance; Introduction The process of localization of waves has been observed in several physical phenomena, such as for excitons in semiconductor nanostructures [1] and

Photocurrent generation in carbon nanotube/cubic-phase HfO₂ nanoparticle hybrid nanocomposites

• Protima Rauwel,
• Augustinas Galeckas,
• Martin Salumaa,
• Frédérique Ducroquet and
• Erwan Rauwel

Beilstein J. Nanotechnol. 2016, 7, 1075–1085, doi:10.3762/bjnano.7.101

• , the electrons can be optically excited via a series of valence-to-conduction band transitions, resulting in characteristic vHS peaks in absorption spectra. However, since holes are instantly filled with readily available electrons, no excitons are formed, and consequently, no photoluminescence (PL

Optical absorption signature of a self-assembled dye monolayer on graphene

• Tessnim Sghaier,
• Sylvain Le Liepvre,
• Céline Fiorini,
• Ludovic Douillard and
• Fabrice Charra

Beilstein J. Nanotechnol. 2016, 7, 862–868, doi:10.3762/bjnano.7.78

• shifted H-bands are formed, corresponding to collectively excited states and energy bands of delocalized excitons [4][5]. The giant transition dipole moments associated with such excitations result in enhanced optical interactions, e.g., with plasmon resonators in which case a strong-coupling regime can

High-resolution noncontact AFM and Kelvin probe force microscopy investigations of self-assembled photovoltaic donor–acceptor dyads

• Benjamin Grévin,
• Pierre-Olivier Schwartz,
• Laure Biniek,
• Martin Brinkmann,
• Nicolas Leclerc,
• Elena Zaborova and
• Stéphane Méry

Beilstein J. Nanotechnol. 2016, 7, 799–808, doi:10.3762/bjnano.7.71

• ) materials, arranged in interpenetrated networks at the 10 nm scale to efficiently separate the excitons into free charges at the D–A interface. In the past decade, several studies demonstrated that Kelvin probe force microscopy (KPFM) can be powerfully combined with atomic force microscopy (AFM) to

Bacteriorhodopsin–ZnO hybrid as a potential sensing element for low-temperature detection of ethanol vapour

• Saurav Kumar,
• Sudeshna Bagchi,
• Senthil Prasad,
• Anupma Sharma,
• Ritesh Kumar,
• Rishemjit Kaur,
• Jagvir Singh and
• Amol P. Bhondekar

Beilstein J. Nanotechnol. 2016, 7, 501–510, doi:10.3762/bjnano.7.44

• the band edge emission, and the emission around 383 nm may be attributed to the recombination of free excitons through an exciton–exciton collision process [48][49]. Also, the peak positions were almost same in ZnO-TF and ZnO-TF/bR, whereas a red shift of 6 nm was observed in ZnO-NR and ZnO-NR/bR

Synthesis and applications of carbon nanomaterials for energy generation and storage

• Marco Notarianni,
• Jinzhang Liu,
• Kristy Vernon and
• Nunzio Motta

Beilstein J. Nanotechnol. 2016, 7, 149–196, doi:10.3762/bjnano.7.17

A single-source precursor route to anisotropic halogen-doped zinc oxide particles as a promising candidate for new transparent conducting oxide materials

• Daniela Lehr,
• Markus R. Wagner,
• Johanna Flock,
• Julian S. Reparaz,
• Clivia M. Sotomayor Torres,
• Alexander Klaiber,
• Thomas Dekorsy and
• Sebastian Polarz

Beilstein J. Nanotechnol. 2015, 6, 2161–2172, doi:10.3762/bjnano.6.222

• with typical shallow donor bound excitons in the neutral charge state and is found very close to the well-known position of the shallow Ga donor D0X I8 or Al D0X I6 [73]. In addition an emission line at 3.333 eV is visible in the spectra of ZnO1−xClx with x = 2.5%. This transition, which is labeled Y0

Current–voltage characteristics of manganite–titanite perovskite junctions

• Benedikt Ifland,
• Patrick Peretzki,
• Birte Kressdorf,
• Philipp Saring,
• Andreas Kelling,
• Michael Seibt and
• Christian Jooss

Beilstein J. Nanotechnol. 2015, 6, 1467–1484, doi:10.3762/bjnano.6.152

• fullerene C61-butyric acid methyl ester (PCBM) and µh = 5.0 × 10–7 cm2/V·s in the hole-doped polymer poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-p-phenylenevinylene) (MDMO–PPV) [2]. Absorption of photons leads to formation of tightly bound excitons that have a very low probability of dissociation. The exciton

• recombination mechanisms in polymer–fullerene solar cells. They concluded that in their devices, the recombination is a trap-assisted recombination at lower voltages and surface recombination at higher voltages. However, intramolecular recombination of excitons at traps within single-blend compounds depends

Electronic interaction in composites of a conjugated polymer and carbon nanotubes: first-principles calculation and photophysical approaches

• Florian Massuyeau,
• Jany Wéry,
• Jean-Luc Duvail,
• Serge Lefrant,
• Abu Yaya,
• Chris Ewels and
• Eric Faulques

Beilstein J. Nanotechnol. 2015, 6, 1138–1144, doi:10.3762/bjnano.6.115

• bandgap depending of their chirality. This fundamental physical difference will have tremendous importance as concerns the electronic coupling, the energy transfer and the migration of excitons between the semi-conducting polymer and the nanotubes [15]. Therefore, the results are compared with original

• photoconductivity and PL behavior can be attributed to the dissociation of excitons and migration of charges onto the SWNTs. Other composite nanomaterials such as MEH-PPV/CdS, CdSe, MEH-PPV/silica, and PPV/TiO2 show a similar PL quenching when the mass percentage of nanomaterials introduced into the conjugated

• separation of photogenerated excitons at polymer/SWNT interfaces across the heterojunctions. The radiative channel only occurs if the excitons remain trapped on short conjugated segments or migrate on longer PPV segments without encountering the SWNT network. In fact, the migration process is likely to

Structural, optical, opto-thermal and thermal properties of ZnS–PVA nanofluids synthesized through a radiolytic approach

• Alireza Kharazmi,
• Nastaran Faraji,
• Roslina Mat Hussin,
• Elias Saion,
• W. Mahmood Mat Yunus and
• Kasra Behzad

Beilstein J. Nanotechnol. 2015, 6, 529–536, doi:10.3762/bjnano.6.55

• to increasing particles size; however, these values are generally higher than the band gap energy of bulk ZnS 3.6 eV [1]. The band gap energy implies a very weak quantum confinement effect. Since the wave functions of electrons and holes are still overlapped, the movement of the excitons instigates a

Bright photoluminescence from ordered arrays of SiGe nanowires grown on Si(111)

• D. J. Lockwood,
• N. L. Rowell,
• A. Benkouider,
• A. Ronda,
• L. Favre and
• I. Berbezier

Beilstein J. Nanotechnol. 2014, 5, 2498–2504, doi:10.3762/bjnano.5.259

• , the Si substrate PL becomes sufficiently quenched from the increasing dissociation of multiple-donor bound excitons within the substrate [31] that the underlying NW PL is more readily seen. By 25 K, only the sharp line at 1092.5 meV due to the Si substrate remains. From now on we shall consider only

Silicon and germanium nanocrystals: properties and characterization

• Ivana Capan,
• Alexandra Carvalho and
• José Coutinho

Beilstein J. Nanotechnol. 2014, 5, 1787–1794, doi:10.3762/bjnano.5.189

• . Notwithstanding, the introduction of dopants in Si NCs has been unequivocally demonstrated, for instance by monitoring the 31P hyperfine splitting of the phosphorous donor state during electron paramagnetic resonance experiments [56], or from photoluminescent transitions of bound excitons to boron [57]. In small

Controlling the optical and structural properties of ZnS–AgInS₂ nanocrystals by using a photo-induced process

• Takashi Yatsui,
• Fumihiro Morigaki and
• Tadashi Kawazoe

Beilstein J. Nanotechnol. 2014, 5, 1767–1773, doi:10.3762/bjnano.5.187

• takes place in the areas with defects as a result of local oxidation–reduction reactions after the excited electron–hole pairs have relaxed to those defect areas in ZAIS nanocrystals (Figure 1a). During the photo-synthesis of ZAIS nanocrystals with the illumination photon energies exceeding Eg, excitons

An insight into the mechanism of charge-transfer of hybrid polymer:ternary/quaternary chalcopyrite colloidal nanocrystals

• Parul Chawla,
• Son Singh and
• Shailesh Narain Sharma

Beilstein J. Nanotechnol. 2014, 5, 1235–1244, doi:10.3762/bjnano.5.137

• polymer P3HT, the generation of excitons takes place (process 1). The excitons then diffuse to the polymer–chalcopyrite interface where charge separation occurs (process 2). The overall energetic driving force ∆E for the electron transfer from the donor to the acceptor depends on the energy difference

• the D/A interface, electron–hole pairs may remain coulombically bound and therefore susceptible to interfacial recombination. The local junction morphology and the crystallinity of both organic and inorganic components greatly affects such charge-transfer (CT) excitons. In the present case (Figure 11

• . Generation of excitons (1), charge separation (2) and current generation (3) for (a) P3HT:CISe, (b) P3HT:CIGSe and (c) P3HT:CZTSe nanocomposites. Acknowledgements The authors are grateful to Prof. R.C. Budhani, Director (NPL) for his constant support and guidance. The authors gratefully acknowledge funding

Optical and structural characterization of oleic acid-stabilized CdTe nanocrystals for solution thin film processing

• Claudio Davet Gutiérrez-Lazos,
• Mauricio Ortega-López,
• Manuel A. Pérez-Guzmán,
• A. Mauricio Espinoza-Rivas,
• Francisco Solís-Pomar,
• Rebeca Ortega-Amaya,
• L. Gerardo Silva-Vidaurri,
• Virginia C. Castro-Peña and
• Eduardo Pérez-Tijerina

Beilstein J. Nanotechnol. 2014, 5, 881–886, doi:10.3762/bjnano.5.100

• technique to assess the structure of semiconductors also at the nanometer-scale. In particular, Raman spectroscopy is sensitive to size effects, because like the excitons, phonons experience quantum confinement effects depending on the crystal size. In CdTe, the quantum confinement effect is revealed by the

Effects of the preparation method on the structure and the visible-light photocatalytic activity of Ag₂CrO₄

• Difa Xu,
• Shaowen Cao,
• Jinfeng Zhang,
• Bei Cheng and
• Jiaguo Yu

Beilstein J. Nanotechnol. 2014, 5, 658–666, doi:10.3762/bjnano.5.77

• the smaller particle size, higher surface area, relatively stronger light absorption, and blue-shift absorption edge, which result in the adsorption of more MB molecules, a shorter diffusion process of more photogenerated excitons, and a stronger oxidation ability of the photogenerated holes

• Ag2CrO4photocatalyst shows the best activity in the photodegradation of a MB aqueous solution, because of the higher adsorption of MB molecules, shorter diffusion process of more photogenerated excitons, and stronger oxidation ability of the photogenerated holes. The current investigation may provide new insight into