Double tungstate lasers: From bulk toward on-chip integrated waveguide devices

It has been recognized that the monoclinic double tungstates $KY{(WO_4)}_2$, $KGd{(WO_4)}_2$, and $KLu{(WO_4)}_2$ possess a high potential as rare-earth-ion-doped solid-state laser materials, partly due to the high absorption and emission cross sections of rare-earth ions when doped into these materials. Besides, their high refractive indexes make these materials potentially suitable for applications that require optical gain and high power in integrated optics, with rather high integration density. We review the recent advances in the field of bulk lasers in these materials and present our work toward the demonstration of waveguide lasers and their integration with other optical structures on a chip

High Spatial Resolution Quantitative Imaging by Cross-calibration Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry and Synchrotron Micro-X-ray Fluorescence Technique

High spatial resolution, quantitative chemical imaging is of importance to various scientific communities, however high spatial resolution and robust quantification are not trivial to attain at the same time. In order to achieve microscopic chemical imaging with enhanced quantification capabilities, the current study links the independent and complementary advantages of two micro-analytical techniques – Synchrotron Radiation-based micro X-ray Fluorescence (SR-microXRF) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). A cross-calibration approach is established between these two techniques and validated by one experimental demonstration. In the presented test case, the diffusion pattern of trace level Cs migrating into a heterogeneous geological medium is imaged quantitatively with high spatial resolution. The one-dimensional line scans and the two-dimensional chemical images reveal two distinct types of geochemical domains: calcium carbonate rich domains and clay rich domains. During the diffusion, Cs shows a much higher interfacial reactivity within the clay rich domain, and turns out to be nearly non-reactive in the calcium carbonate domains. Such information obtained on the micrometer scale improves our chemical knowledge concerning reactive solute transport mechanism in heterogeneous media. Related to the chosen demonstration study, the outcome of the quantitative, microscopic chemical imaging contributes to a refined safety assessment of potential host rock materials for deep-geological nuclear waste storage repositories

EXAFS Structural Determination of the Pt2(P2O5H2)44– Anion in Solution

We present the first structural determination of the Pt2(P2O5H2)44– anion in solution by analyzing the extended X-ray absorption fine structure (EXAFS) spectrum of the Pt LIII edge. The data could be fit with a simple model involving single and multiple scattering paths to near and far P-atoms, bridging O-atoms, and the other Pt-atom in the binuclear complex. A Pt–Pt distance of 2.876(28) Å and a Pt–P bond length of 2.32(4) Å are obtained. These values are in line with distances found in previous X-ray diffraction studies. The assignment of the EXAFS spectrum of the Pt2(P2O5H2)44– anion in its ground state is required for future time-resolved X-ray absorption measurements with the goal of determining the structure and dynamics of the complex in the 1,3A2u excited states

Microbial activity affects sulphur in biogenic aragonite

Carbonates that exhibit obvious diagenetic alteration are usually excluded as archives in palaeoenvironmental studies. However, the potential impact of microbial alteration during early diagenesis is still poorly explored. To investigate the sensitivity of sulphur concentration, distribution, oxidation state and isotopic composition in marine aragonite to microbial alteration, Arctica islandica bivalves and Porites sp. corals were experimentally exposed to anaerobic microbial activity. The anoxic incubation media included a benthic bacterial strain Shewanella sediminis and a natural anoxic sediment slurry with a natural microbial community of unknown species. Combined fluorescence microscopy and synchrotron‐based analysis of the sulphur distribution and oxidation state enabled a comparison of organic matter and sulphur content in the two materials. Results revealed a higher proportion of reduced sulphur species and locally stronger fluorescence within the pristine bivalve shell compared to the pristine coral skeleton. Within the pristine bivalve specimen, reduced sulphur was enriched in layers along the inner shell margin. After incubation in the anoxic sediment slurry, this region revealed rust‐brown staining and a patchy S2‐ distribution pattern rather than S2‐‐layers. Another effect on sulphur distribution was rust‐brown coloured fibres along one growth line, revealing a locally higher proportion of sulphur. The δ34S value of carbonate‐associated sulphate remained largely unaffected by both incubation media, but a lower δ34S value of water‐soluble sulphate reflected the degradation of insoluble organic matter by microbes in both experiments. No significant alteration was detected in the coral samples exposed to microbial alteration. The data clearly identified a distinct sensitivity of organically bound sulphur in biogenic aragonite to microbial alteration even when “traditional” geochemical proxies such as δ18OCARB or δ13CCARB in the carbonate didn’t show any effect. Differences in the intensity of microbial alteration documented are likely due to inherent variations in the concentration and nature of original organic compositions in the samples

Phosphorus speciation in the organic layer of two Swedish forest soils 13-24 years after wood ash and nitrogen application

Application of wood ash to forests can restore pools of phosphorus (P) and other nutrients, which are removed following whole tree harvesting. Yet, the mechanisms that affect the fate of ash-P in the organic layer are less well known. Previous research into the extent to which ash application leads to increased P solubility in the soil is contradictory. We combined synchrotron P K-edge XANES spectroscopy, mu-XRF microscopy, and chemical ex-tractions to examine the speciation and solubility of P. We studied organic horizons of two long-term field ex-periments, Riddarhyttan (central Sweden), which had received 3, 6, and 9 Mg ash ha -1, and Ro center dot dalund (northern Sweden), where 3 Mg ash ha- 1 had been applied alone or combined with N every-three years since 2003. At the latter site, we also determined P in aboveground tree biomass. Overall, the ash application increased P in the organic layer by between 6 and 28 kg P ha -1, equivalent to 17-39 % of the initial P content in the applied ash. At Ro center dot dalund, there was 4.6 kg Ca-bound P ha- 1 (9.5 %) in the ash treatment compared to 1.6 kg ha- 1 in the ash + N treatment and < 0.4 kg ha- 1 in the N treatment and the control. At Riddarhyttan, only the treatment with the highest ash dose had residual Ca-bound P (3.8 kg ha -1). In contrast, the ash application increased Al-bound P (p < 0.001) with up to 15.6 kg P ha -1. Moreover, the ash increased Olsen-P by up to two times. There was a strong relationship between the concentrations of Olsen-P and Al-bound P (R2 = 0.83, p < 0.001) as well as Fe-bound P (R2 = 0.74, p = 0.003), suggesting that the ash application resulted in an increased amount of relatively soluble P associated with hydroxy-Al and hydroxy-Fe compounds. Further, there was an 18 % increase in P uptake by trees in the ash treatment. By contrast, repeated N fertilization, with or without ash, reduced Olsen-P. The lower P extractability was concomitant with a 39 % increase in plant P uptake in the N treatment, which indicates elevated P uptake in response to higher N availability. Hence, the application of wood ash increased Al-bound P, easily available P, and P uptake. N fertilization, while also increasing tree P uptake, instead decreased easily available P and did not cause a shift in soil P speciation

Retrieving photochemically active structures by time-resolved EXAFS spectroscopy

Describing the nature and structure of molecular excited states is important in order to understand their chemical reactivity and role as intermediates in photochemical reactions. The recent implementation of x-ray absorption spectroscopy in the ultrafast time domain allows studying the electronic and structural dynamics of photochemically active molecules in solutions. In this work we present the structural determination of a photoexcited diplatinum molecule, [Pt-2(P2O5H2)(4)](4-), which plays a photocatalytic role in important chemical conversions. A novel analysis of time-resolved EXAFS spectra based on the fitting of the experimental transients obtained from optical pump/x-ray probe experiments has been performed to derive a contraction of 0.31(5) angstrom of the two Pt atoms and a ligand expansion of 0.010(6) angstrom. The former is assigned to the formation of a transient Pt-Pt bond in the excited state, while the latter indicates a concomitant weakening of the Pt-ligand coordination bonds

Phosphorus speciation in the organic layer of two Swedish forest soils 13–24 years after wood ash and nitrogen application

Application of wood ash to forests can restore pools of phosphorus (P) and other nutrients, which are removed following whole tree harvesting. Yet, the mechanisms that affect the fate of ash-P in the organic layer are less well known. Previous research into the extent to which ash application leads to increased P solubility in the soil is contradictory. We combined synchrotron P K-edge XANES spectroscopy, µ-XRF microscopy, and chemical extractions to examine the speciation and solubility of P. We studied organic horizons of two long-term field experiments, Riddarhyttan (central Sweden), which had received 3, 6, and 9 Mg ash ha−1, and Rödålund (northern Sweden), where 3 Mg ash ha−1 had been applied alone or combined with N every-three years since 2003. At the latter site, we also determined P in aboveground tree biomass. Overall, the ash application increased P in the organic layer by between 6 and 28 kg P ha−1, equivalent to 17–39 % of the initial P content in the applied ash. At Rödålund, there was 4.6 kg Ca-bound P ha−1 (9.5 %) in the ash treatment compared to 1.6 kg ha−1 in the ash + N treatment and < 0.4 kg ha−1 in the N treatment and the control. At Riddarhyttan, only the treatment with the highest ash dose had residual Ca-bound P (3.8 kg ha−1). In contrast, the ash application increased Al-bound P (p < 0.001) with up to 15.6 kg P ha−1. Moreover, the ash increased Olsen-P by up to two times. There was a strong relationship between the concentrations of Olsen-P and Al-bound P (R2 = 0.83, p < 0.001) as well as Fe-bound P (R2 = 0.74, p = 0.003), suggesting that the ash application resulted in an increased amount of relatively soluble P associated with hydroxy-Al and hydroxy-Fe compounds. Further, there was an 18 % increase in P uptake by trees in the ash treatment. By contrast, repeated N fertilization, with or without ash, reduced Olsen-P. The lower P extractability was concomitant with a 39 % increase in plant P uptake in the N treatment, which indicates elevated P uptake in response to higher N availability. Hence, the application of wood ash increased Al-bound P, easily available P, and P uptake. N fertilization, while also increasing tree P uptake, instead decreased easily available P and did not cause a shift in soil P speciation

Fabrication of 2- and 3-Dimensional Nanostructures

Amongst tools for fabricating periodic and aperiodic nanostructures and nanodevices, electron beam-induced organometallic chemical vapor deposition (E-OMCVD) offers a highly flexible and controllable one-step deposition process. E-OMCVD enables maskless fabrication of nanoscale research and custom structures that have least dimensions near or below 10 nm–a scale at which other methods prove difficult or costly. Using the focused electron beam in a modified HB501 field-emission scanning transmission electron microscope (STEM), pads and wires with uniform thickness and well-defined shapes have been defined and deposited. Although conditions for fabricating the smallest deposits have not yet been optimized, the edge acuity (sharpness) of the deposits is consistently as low as 4 nm or less and the corresponding smallest wire width is 8 nm. Under different deposition conditions, three-dimensional open structured nanonetworks have been fabricated. Results of an investigation of E-OMCVD parameters are presented for the metallocene compound, nickelocene (Ni(Csub-5Hsub-5)sub-2), as source organometallic