Retraction: On the enzymatic activity of catalase: an iron L-edge X-ray absorption study of the active centre.

Retraction of 'On the enzymatic activity of catalase: an iron L-edge X-ray absorption study of the active centre' by Nora Bergmann et al., Phys. Chem.

In Situ PL and SPV Monitored Charge Carrier Injection During Metal Assisted Etching of Intrinsic a-Si Layers on c-Si.

Although hydrogenated amorphous silicon is already widely examined regarding its structural and electronic properties, the chemical etching behavior of this material is only roughly understood. We present a detailed study of the etching properties of intrinsic hydrogenated amorphous silicon, (i)a-Si:H, layers on crystalline silicon, c-Si, within the framework of metal assisted chemical etching (MACE) using silver nanoparticles (Ag NPs). The etching processes are examined by in situ photoluminescence (PL) and in situ surface photovoltage (SPV) measurements, as these techniques allow a monitoring of the hole injection that takes place during MACE.

Strongly reduced Si surface recombination by charge injection during etching in diluted HF/HNO3.

Herein, we investigate the behaviour of the surface recombination of light-induced charge carriers during the etching of Si in alkaline (KOH) and acidic etching solutions of HF/HNO(3)/CH(3)COOH (HNA) or HF/HNO(3)/H(3)PO(4) (HNP) at different concentration ratios of HF and HNO(3) by means of photoluminescence (PL) measurements. The surface recombination velocity is strongly reduced during the first stages of etching in HF/HNO(3)-containing solutions pointing to a interface well passivated by the etching process, where a positive surface charge is induced by hole injection from NO-related surface species into the Si near-surface region (back surface field effect). This injected charge leads to a change in band bending by about 150 mV that repulses the light-induced charge carriers from the surface and therefore enhances the photoluminescence intensity, since non-radiative surface recombination is reduced.

On the enzymatic activity of catalase: an iron L-edge X-ray absorption study of the active centre.

Catalase and methaemoglobin have very similar haem groups, which are both ferric, yet catalase decomposes hydrogen peroxide to water and oxygen very efficiently, while methaemoglobin does not. Structural studies have attributed this behaviour to their different distal environments. Here we present Fe L(2,3)-edge X-ray absorption spectra of these proteins in physiological solutions, which reveal clear differences in their electronic structures, in that pi back-donation of the Fe atom occurs in catalase, which confers on it a partial ferryl (Fe(4+)) character, while this is not the case in methaemoglobin.