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

• breakthroughs in photovoltaics. It is believed that quantum dot (QD) solar cells have the potential to reach a maximum conversion efficiency of about 66% [2]. A colloidal nanocrystal solar cell, which combines all the advantages of organics (scalable and controllable synthesis) with transport properties

In vitro interaction of colloidal nanoparticles with mammalian cells: What have we learned thus far?

• Moritz Nazarenus,
• Qian Zhang,
• Mahmoud G. Soliman,
• Pablo del Pino,
• Beatriz Pelaz,
• Susana Carregal-Romero,
• Joanna Rejman,
• Barbara Rothen-Rutishauser,
• Martin J. D. Clift,
• Reinhard Zellner,
• G. Ulrich Nienhaus,
• James B. Delehanty,
• Igor L. Medintz and
• Wolfgang J. Parak

Beilstein J. Nanotechnol. 2014, 5, 1477–1490, doi:10.3762/bjnano.5.161

• semiconductor quantum dot NPs (QDs) were unable to elicit a more negative biological effect when used for cellular labeling than a panel of dyes commonly used for the same intrinsic purposes [159]. Along with this, often transformed and immortalized cell lines are used in biological research, meaning that they

PEGylated versus non-PEGylated magnetic nanoparticles as camptothecin delivery system

• Paula M. Castillo,
• Mario de la Mata,
• Maria F. Casula,
• José A. Sánchez-Alcázar and
• Ana P. Zaderenko

Beilstein J. Nanotechnol. 2014, 5, 1312–1319, doi:10.3762/bjnano.5.144

• electrophoretic techniques have also been developed in order to quantitatively determine the number of PEG molecules in gold and quantum dot-PEG conjugates [43]. Loading of CPT on USM and USM-PEG nanoparticles was performed by direct incubation of the drug in an aqueous solution of the nanoparticles to obtain the

Nanostructure sensitization of transition metal oxides for visible-light photocatalysis

• Hongjun Chen and
• Lianzhou Wang

Beilstein J. Nanotechnol. 2014, 5, 696–710, doi:10.3762/bjnano.5.82

• greatly prolonged lifetime of photoexcited carriers [36]. We also investigated the photoelectrochemical behavior of CdS sensitized TiO2 film with {001} facet enriched anatase nanocrystals [37]. Zhang et al. developed a double-sided CdS and CdSe quantum dot co-sensitized ZnO nanowire arrayed photoanode for

• [38]. A synergetic effect of nitrogen-doping and CdSe quantum-dot-sensitization on nanocrystalline TiO2 was also investigated. Interestingly, a significant photoelectrochemical hydrogen generation enhancement was observed due to CdSe sensitization and N-doping that can facilitate hole transport from

• ][44], CdTe quantum dot monolayer sensitized ZnO nanowire [45], CdS nanoparticle/ZnO nanowire array [46][47], CdS/ TiO2 nanofibers heteroarchitectures [48], ZnO/CdS core/shell nanowire [49], CdS nanowires decorated with TiO2 nanoparticles [50], and their potential applications for photoelectrochemical

A visible-light-driven composite photocatalyst of TiO₂ nanotube arrays and graphene quantum dots

• Donald K. L. Chan,
• Po Ling Cheung and
• Jimmy C. Yu

Beilstein J. Nanotechnol. 2014, 5, 689–695, doi:10.3762/bjnano.5.81

• incorporation of graphene quantum dots could extend the photo-response of the nanotubes to the visible-light range. Graphene quantum dot-sensitized TiO2 nanotube arrays were synthesized by covalently coupling these two materials. The product was characterized by Fourier-transform infrared spectrometry (FTIR

Study of mesoporous CdS-quantum-dot-sensitized TiO₂ films by using X-ray photoelectron spectroscopy and AFM

• Mohamed N. Ghazzal,
• Robert Wojcieszak,
• Gijo Raj and
• Eric M. Gaigneaux

Beilstein J. Nanotechnol. 2014, 5, 68–76, doi:10.3762/bjnano.5.6

Energy transfer in complexes of water-soluble quantum dots and chlorin e6 molecules in different environments

• Irina V. Martynenko,
• Anna O. Orlova,
• Vladimir G. Maslov,
• Alexander V. Baranov,
• Anatoly V. Fedorov and
• Mikhail Artemyev

Beilstein J. Nanotechnol. 2013, 4, 895–902, doi:10.3762/bjnano.4.101

• oxide (TOPO), cysteamine, 2-(dimethylamino)ethanethiol (DMAET), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDAC) were purchased from Aldrich. Poly(ethylene terephthalate) (PET) membranes were obtained from FLNR JINR (Dubna, Russia). Quantum dot synthesis All semiconductor quantum dots

Challenges in realizing ultraflat materials surfaces

• Takashi Yatsui,
• Wataru Nomura,
• Fabrice Stehlin,
• Olivier Soppera,
• Makoto Naruse and
• Motoichi Ohtsu

Beilstein J. Nanotechnol. 2013, 4, 875–885, doi:10.3762/bjnano.4.99

• principles and concepts of DPP technology differ significantly from those of conventional wave-optical technologies such as photonic crystals [29], plasmonics [30], metamaterials [31], or quantum-dot photonic devices [32], in which the size and function are governed by the light diffraction limit. Therefore

Magnetic anisotropy of graphene quantum dots decorated with a ruthenium adatom

• Igor Beljakov,
• Velimir Meded,
• Franz Symalla,
• Karin Fink,
• Sam Shallcross and
• Wolfgang Wenzel

Beilstein J. Nanotechnol. 2013, 4, 441–445, doi:10.3762/bjnano.4.51

• close to the edge, while the opposite is true for the zigzag edge. Additionally, in-plane pinning of the magnetization direction perpendicular to the edge itself is observed for the first time. Keywords: adsorbate; grapheme; graphene quantum dot; magnetic anisotropy; transition metal; Introduction

• spin polarisation of the ZGQD arises from a highly localized pz-type edge state [26], and the total moment of the quantum dot is exactly equal to the difference in number between the A-type atoms and B-type atoms, in agreement with the theorem of magnetism in a bipartite lattice at half filling

Horizontal versus vertical charge and energy transfer in hybrid assemblies of semiconductor nanoparticles

• Gilad Gotesman,
• Rahamim Guliamov and
• Ron Naaman

Beilstein J. Nanotechnol. 2012, 3, 629–636, doi:10.3762/bjnano.3.72

• [10], or TiO2 devices [11][12] as the conductive substrates, have also been reported. Long-range resonance energy transfer was shown in mixtures of donor and acceptor close-packed arrays of NPs (quantum dot solids, QDS) [13][14][15]. Furthermore, studies on multilayered NP arrays, prepared by layer-by

P-wave Cooper pair splitting

• Henning Soller and
• Andreas Komnik

Beilstein J. Nanotechnol. 2012, 3, 493–500, doi:10.3762/bjnano.3.56

• resonant level between a superconductor and two ferromagnets: where Γ is the tunnel rate through the two barriers between the quantum dot and the ferromagnets (both are assumed to be equal) and ΓS is the tunnel rate between the superconductor and the quantum dot. Δd refers to the energy of the resonant

• moments) of P(q). We model the superconductor–ferromagnet beam splitter as two ferromagnets F1 and F2 that are tunnel-coupled to a resonant level, which is the simplest model of a quantum dot. The superconductor is also coupled to the resonant level via HT1 and HT2, which takes into account the interface

• effects. The result is the Hamiltonian where represents the resonant level. Throughout the rest of this exposition we use units in which e = = kB = 1 and restrict ourselves to a quantum dot on resonance Δd = 0. Ferromagnetic electrodes are described in the language of electron field operators Ψk,α,σ

Combining nanoscale manipulation with macroscale relocation of single quantum dots

• Francesca Paola Quacquarelli,
• Richard A. J. Woolley,
• Martin Humphry,
• Jasbiner Chauhan,
• Philip J. Moriarty and
• Ashley Cadby

Beilstein J. Nanotechnol. 2012, 3, 324–328, doi:10.3762/bjnano.3.36

• ) based on electro-osmotic flow control (EOFC) [11][12] have resulted in a positioning precision of 130 nm when particle diffusion is suppressed. In a challenging recent experiment, atomic force microscopy (AFM) was used to manipulate a single gold nanoparticle (≈35 nm) to approach a single quantum dot

• patterning procedure allows us to (re-)locate a given, previously positioned, QD in any optical system. To manipulate and characterise a single quantum dot we required the ability to repeatedly address an area of only a few square nanometres on a 10 × 10 mm2 substrate. In order to realise this relocation

• still emit at the expected central wavelength and are highly luminescent. The manipulation of each quantum dot requires several hours of intensive AFM work by a highly skilled operator, and thus this is hardly a cost-effective, scalable process. To address this issue, we have taken steps to automate the

Current-induced forces in mesoscopic systems: A scattering-matrix approach

• Niels Bode,
• Silvia Viola Kusminskiy,
• Reinhold Egger and
• Felix von Oppen

Beilstein J. Nanotechnol. 2012, 3, 144–162, doi:10.3762/bjnano.3.15

• dependence in the hybridization between the leads and the quantum dot, allowing more flexibility for modeling real systems. In the section “Microscopic derivation of the Langevin equation”, we introduce the theoretical model, and derive the equations of motion of the mechanical degrees of freedom starting

• the Langevin equation The model We model the system as a mesoscopic quantum dot connected to multiple leads and coupled to vibrational degrees of freedom. Throughout this work we consider noninteracting electrons and we set = 1. The Hamiltonian for the full system reads where the different terms are

• introduced in the following. We describe the quantum dot by M electronic levels coupled to N slow collective degrees of freedom . This is contained in the Hamiltonian of the dot which describes the electronic levels of the dot and their dependence on the coordinates of the collective modes, (), by the

Distance dependence of near-field fluorescence enhancement and quenching of single quantum dots

• Volker Walhorn,
• Jan Paskarbeit,
• Heinrich Gotthard Frey,
• Alexander Harder and
• Dario Anselmetti

Beilstein J. Nanotechnol. 2011, 2, 645–652, doi:10.3762/bjnano.2.68

• the dependence of the fluorescence emission from a single quantum dot on the distance from the gold coated cantilever tip apex, we acquired the fluorescence emission intensity at several z-distances. After each 2.5 nm step, 200 frames with an exposure time of 50 ms were obtained. The measurements

• glass cover slips and dried. Sparsely covered (<1 quantum dot per 25 µm2) samples allowed the addressing of individual fluorophores. Silicon AFM cantilevers (PPP-NCHR, Nanosensors, Neuchatel, Switzerland) were washed with acetone, ethanol and water and dried in a gentle flow of nitrogen. Subsequently, a

• the sample surface at an angle of total reflection. The intensity of the evanescent wave projecting beyond the cover slip decreases exponentially. An image-intensified CCD camera detects the fluorescence light. b) Single CCD camera frame of a single quantum dot. Integrated fluorescence intensity of a

Room temperature excitation spectroscopy of single quantum dots

• Christian Blum,
• Frank Schleifenbaum,
• Martijn Stopel,
• Sébastien Peter,
• Marcus Sackrow,
• Vinod Subramaniam and
• Alfred J. Meixner

Beilstein J. Nanotechnol. 2011, 2, 516–524, doi:10.3762/bjnano.2.56

• any measures to suppress or minimize blinking. The single quantum dot excitation spectra recorded exhibited the main characteristics of a declining slope from shorter to longer wavelengths, and a peak close to the band edge transition, which we identify as the 1S(e)-2S3/2(h) transition [39]. However

• a single quantum dot is shown in Figure 1a. In contrast to the ensemble spectrum, we observed distinct dips and gaps in the single quantum dot excitation spectra, which in principle could either result from blinking or reflect the photophysical properties of the quantum dot. Semiconductor quantum

• are characteristic of the emission from a single emitter. These fluctuations have been reported for semiconductor quantum dots, and have only recently been circumvented in exceptional cases [42][43][44]. The intensity blinking of the quantum dot can be visualized from the intensity trajectories that

Simple theoretical analysis of the photoemission from quantum confined effective mass superlattices of optoelectronic materials

• Debashis De,
• Sitangshu Bhattacharya,
• S. M. Adhikari,
• A. Kumar,
• P. K. Bose and
• K. P. Ghatak

Beilstein J. Nanotechnol. 2011, 2, 339–362, doi:10.3762/bjnano.2.40

• intensity reflects the direct signature of light waves on the carrier energy spectra. The content of this paper finds six different applications in the fields of low dimensional systems in general. Keywords: magnetic quantization; photoemission; quantum dot effective mass superlattices; quantum well

• cases defined by the perturbed two band model of Kane or a parabolic energy band, β0(E, λ, Eg0i, Δi) should be replaced by τ0(E, λ, Eg0i) and ρ0(E, λ, Eg0i) respectively. The basic forms of Equation 12 and Equation 13 remain unchanged. 3 Photoemission from quantum dot effective mass superlattices The

• . In this paper, we have studied the photoemission from quantum wire and quantum dot effective mass superlattices of optoelectronic materials, on the basis of newly formulated electron dispersion relations, in the presence of external photo-excitation. In addition, the influence of magnetic field on

Dense lying self-organized GaAsSb quantum dots on GaAs for efficient lasers

• Thomas H. Loeber,
• Dirk Hoffmann and
• Henning Fouckhardt

Beilstein J. Nanotechnol. 2011, 2, 333–338, doi:10.3762/bjnano.2.39

• . Apparently, a V/III ratio of 1/1 is optimal for high quantum dot density. Compared to the highest QD density previously reported, our results reveal a two times higher density. Figure 2 shows the PL spectra of two QD samples grown at a V/III ratio of 1/1 (so-called smaller dots) and 1.5/1 (larger dots

• compared to our work. According to Figure 2 an increase in the dot volume should lead to a redshift of the PL peak. However, the blueshift induced by the decreased Sb concentration in the QDs overcompensates for the volume dependent redshift, leading to the net blueshift observed in Figure 4. Quantum dot

• × 1010 cm−2 was achieved in the SK epitaxial growth mode, with a V/III flux ratio of 1/1 at a growth temperature of T = 527 °C and nominal coverage of 3 ML. With increasing V/III ratio the dot size also increased. Only one PL peak was detected, attributable to the quantum dot nature; no further peak

Fabrication and spectroscopic studies on highly luminescent CdSe/CdS nanorod polymer composites

• Jana Bomm,
• Andreas Büchtemann,
• Angela Fiore,
• Liberato Manna,
• James H. Nelson,
• Diana Hill and
• Wilfried G. J. H. M. van Sark

Beilstein J. Nanotechnol. 2010, 1, 94–100, doi:10.3762/bjnano.1.11

• , aggregation of nanoparticles, loss of transparency and luminescence quenching due to exciton energy transfer [2][7]. Several methods have been described to overcome these problems for quantum dot polymer composites. For example, Bawendi and coworkers incorporated trioctylphosphine oxide covered CdSe/ZnS QDs