Dopant profiling in silicon nanowires measured by scanning capacitance microscopy

Silicon nanowires (SiNWs) with axial doping junctions were synthesized via the Au‐catalyzed vapor–liquid–solid growth method with the use of HCl. In this work, dopant profiling from three axially doped SiNWs with p–i, p–n and n–i–p junctions were investigated using both scanning electron microscopy (SEM) and scanning capacitance microscopy (SCM). It turns out that observed doping contrasts in SEM are also affected by the surface roughness and sample charging. In contrast, SCM allows us to delineate with sub‐10 nm resolution the electrical junctions and provides a relative value of the doping concentration in each segment of the NW. SCM clearly evidences the expected doping regions within these SiNWs thanks to the addition of HCl during the growth that strongly prevents shell overgrowth. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of kosmotrope and chaotrope anions on rate and equilibria processes for the α-cyclodextrin catalysed reaction of 3-chloroperbenzoic acid with iodide

Solutes, ranging from small hydrophobic molecules to macromolecular structures such as proteins, are heavily influenced by the presence of salts, particularly the anionic component. It is well known that anions possessing a high charge density, such as sulfate, are able to reduce the solubility of these solutes, with this effect likely to be entropically driven and based on the influence the anions have on the structure of water. Other anions with a lower charge density, such as perchlorate, can have the opposite effect, improving solubility. The current consensus for the latter effect is that rather than being as a result of changes to water structure, it is due to specific binding of the anions to solute molecules, acting to reduce unfavourable interactions with the solvent. In this paper we report on how both sulfate and perchlorate influence binding and catalysis for the α-cyclodextrin mediated reaction of iodide with 3-chloroperbenzoic acid (MCPBA) for which the cyclodextrin–MCPBA complex is the catalytic species. Kinetic runs have been carried out over the temperature range 15–35 °C in dilute nitric acid and with added sulfate and perchlorate, allowing the calculation of enthalpies and entropies for the rate and equilibria processes involved in this system. We show that both sulfate and perchlorate demonstrate the expected Hofmeister behaviours, with sulfate acting to exclude the MCPBA from solution into the cyclodextrin cavity, thus increasing the amount of the catalytic species, whereas perchlorate acts to solubilise the MCPBA. Perchlorate has a complex range of effects, since as well as forming an association complex with cyclodextrin, the thermodynamic parameters indicate that it may also associate with MCPBA and the MCPBA–cyclodextrin complex. These associations may explain the catalysis that is observed with increasing perchlorate concentration. The effects observed in this study may be relevant to other binding processes in chemistry and biology.     

Toward a rational design of poly(2,7-carbazole) derivatives for solar cells

On the basis of theoretical models and calculations, several alternating polymeric structures have been investigated to develop optimized poly(2,7-carbazole) derivatives for solar cell applications. Selected low band gap alternating copolymers have been obtained via a Suzuki coupling reaction. A good correlation between DFT theoretical calculations performed on model compounds and the experimental HOMO, LUMO, and band gap energies of the corresponding polymers has been obtained. This study reveals that the alternating copolymer HOMO energy level is mainly fixed by the carbazole moiety, whereas the LUMO energy level is mainly related to the nature of the electron-withdrawing comonomer. However, solar cell performances are not solely driven by the energy levels of the materials. Clearly, the molecular weight and the overall organization of the polymers are other important key parameters to consider when developing new polymers for solar cells. Preliminary measurements have revealed hole mobilities of about 1 x 10(-3) cm2 x V(-1) x s(-1) and a power conversion efficiency (PCE) up to 3.6%. Further improvements are anticipated through a rational design of new symmetric low band gap poly(2,7-carbazole) derivatives.     

Das 1,3‐Dimethylcyanurat‐Ion als ambidenter Ligand

The 1,3‐Dimethylcyanurate Ion as an Ambident Ligand 1,3‐Dimethyl‐2,4,6‐trioxo‐1,3,5‐triazin ( 7 ), (1,3‐dimethylcyanuric acid, DMCH), obtained from the thermolysis of methyl urea, is deprotonated with lithium ethylate. In the resulting dinuclear complex [(DMCLi)₂·4 H₂O] ( 8 ), the heterocyclic anions are linked to the lithium centres with oxygen atoms as its enolate form. In the corresponding silver complex [(DMCAg)₂·en] ( 10 ), (en = ethylendiamine), N‐coordination of the ligand is observed. The crystal structures of 7 , 8 , and 10 reveal the presence of intermolecular hydrogen bonds.     

[Ph4P][(C5H6N3O3)M(CO)5] (M = Cr,Mo, W; C5H7N3O3 = 1,3‐Dimethyl‐cyanuric Acid). Organometallic Complexes of the 1,3‐Dimethylcyanurate Ligand

1,3‐Dimethylcyanuric acid (DMCH) forms on deprotonation and reaction with TlF its thallous salt Tl[DCM] ( 2 ) which is converted to the phosphonium salt [PPh₄][DCM] ( 3 ). On the reaction with M(CO)₆, the pentacarbonylmetalate salts [Ph₄P][(DMC)M(CO)₅], M = Cr ( 4a ), Mo ( 4b ) and W ( 4c ) are obtained. IR and NMR data of 4 reveal the DMC anion ( 1 ) to have coordination properties similar to those of pyridine. The crystal structures of 4a and 4c are reported.     

On the nonlinear Hammerstein integral equations in Banach spaces and application to the boundary value problem of fractional order

In this paper, we study the existence of solutions of the operator equations p+λGfx=x in the Banach space C[I,E]. It is assumed the vector-valued function f is nonlinear Pettis-integrable. Some additional assumptions imposed on f are expressed in terms of a weak measure of noncompactness. To encompass the full scope of the paper, we investigate the existence of pseudo-solutions for the nonlinear boundary value problem of fractional type

under the Pettis integrability assumption imposed on f.     

Compressed lithium atom under Debye screening

In the present paper, we introduced two approximation methods to investigate the spherically compressed lithium atom under the influence of Debye plasma. Specifically, the diffusion and the variational Monte Carlo methods are used for the first time to study this case. We incorporated an exponential screening into the nuclear Coulomb potential to account for the plasma influence. We focused our investigation on analyzing the combined effect of compression and plasma environment on the behavior of the lithium atom in its ground state. The resulting outcomes exhibited consistent pattern across various confinement radii $R_c$ and Debye plasma lengths $\mu$. Many of the results are novel contributions, as they have yet to be explored. Moreover, the findings from this study demonstrated reasonable agreement with the limited existing theoretical results.     

Development of a hypoxia-selective near-infrared fluorescent probe for non-invasive tumor imaging

A near-infrared fluorochrome, GPU-311, was designed, synthesized and evaluated for its application in non-invasive imaging of tumor hypoxia. Efficient synthesis was achieved by nucleophilic substitution and click chemistry ring using the bifunctional tetraethylene glycol linker 2 containing thiol and azide groups for the conjugation of the propargylated nitroimidazole 1 and the heptamethine cyanine dye 3 bearing a 2-chloro-1-cyclohexenyl ring. GPU-311 exhibited long excitation and emission wavelength (Ex/Em=785/802?nm) and a decent quantum yield (0.05). The water solubility and hydrophilicity of GPU-311 increased. After in vitro treatment of SUIT-2/HRE-Luc pancreatic cancer cells with GPU-311, a higher level of fluorescence was observed selectively in hypoxia than in normoxia. However, in vivo fluorescence imaging of a mouse xenograft model after GPU-311 administration revealed inadequate accumulation of GPU-311 in tumors due to its rapid elimination through the liver.     

Electrical and dielectric properties of glass system NaPO3–KHSO4

Glass samples have been prepared in the NaPO₃–KHSO₄ binary system with the classical melting, casting and annealing steps. Electrical and dielectrical properties of glass samples were studied. Measurements of DC and AC conductivity and complex electrical permittivity of xNaPO₃–(100 ? x)KHSO₄ glass system were carried out at temperatures ranging from room temperature to temperature located 15 °C below glass transition temperature T_g. Results showed that changes of NaPO₃ concentration considerably affect values of observed parameters. DC conductivity of glass increases as NaPO₃ concentration grows until concentration x = 60. However, beyond this value a sharp decrease of DC conductivity was observed. In addition relaxation times showed abrupt changes at concentration x = 60, corresponding to the lowest relaxation times at the temperature 90 °C.