Label-Free Direct Identification of MicroRNAs Based on a Narrow Constant-Inner-Diameter Emitter Mass Spectrometry Analysis.

MicroRNAs (miRNAs) are a class of endogenous noncoding small RNAs that play important roles in various biological processes and diseases. Direct determination of miRNAs is a cost-efficient and accurate method for analysis. Herein, we established a novel method for the analysis of miRNAs based on a narrow constant-inner-diameter mass spectrometry emitter. We utilized the gravity-assisted sleeving etching method to prepare a constant-inner-diameter mass spectrometry emitter with a capillary inner diameter of 5.5 µm, coupled it with a high-voltage power supply and a high-resolution mass spectrometer, and used it for miRNA direct detection. The method showed high sensitivity and reproducibility for the analysis of four miRNAs, with a limit of detection of 100 nmol/L (170 amol) for the Hsa-miR-1290 analysis. Compared with commercial ion sources, our method achieved higher sensitivity for miRNA detection. In addition, we analyzed the total miRNAs in the A549 cells. The result indicated that both spiked and endogenous miRNAs could be quantified with high accuracy. As a result, this method offers a promising platform for highly sensitive and accurate miRNA analysis. Furthermore, this approach can be extended to the analysis of other small oligonucleotides and holds the potential for studying clinical samples and facilitating disease diagnosis.

Kinetically Controlled Nucleation Enabled by Tunable Microfluidic Mixing for the Synthesis of Dendritic Au@Pt Core/Shell Nanomaterials.

The nucleation stage plays a decisive role in determining nanocrystal morphology and properties; hence, the ability to regulate nucleation is critical for achieving high-level control. Herein, glass microfluidic chips with S-shaped mixing units are designed for the synthesis of Au@Pt core/shell materials. The use of hydrodynamics to tune the nucleation kinetics is explored by varying the number of mixing units. Dendritic Au@Pt core/shell nanomaterials are controllably synthesized and a formation mechanism is proposed. As-synthesized Au@Pt exhibited excellent ethanol oxidation activity under alkaline conditions (8.4 times that of commercial Pt/C). This approach is also successfully applied to the synthesize of Au@Pd core/shell nanomaterials, thus demonstrating its generality.

Ultra-Large Two-Dimensional Metal Nanowire Networks by Microfluidic Laminar Flow Synthesis for Formic Acid Electrooxidation.

Despite the great research interest in two-dimensional metal nanowire networks (2D MNWNs) due to their large specific surface area and abundance of unsaturated coordination atoms, their controllable synthesis still remains a significant challenge. Herein, a microfluidics laminar flow-based approach is developed, enabling the facile preparation of large-scale 2D structures with diverse alloy compositions, such as PtBi, AuBi, PdBi, PtPdBi, and PtAuCu alloys. Remarkably, these 2D MNWNs can reach sizes up to submillimeter scale (~220 µm), which is significantly larger than the evolution from the 1D or 3D counterparts that typically measure only tens of nanometers. The PdBi 2D MNWNs affords the highest specific activity for formic acid (2669.1 mA mg-1) among current unsupported catalysts, which is 103.5 times higher than Pt-black, respectively. Furthermore, in situ Fourier transform infrared (FTIR) experiments provide comprehensive evidence that PdBi 2D MNWNs catalysts can effectively prevent CO* poisoning, resulting in exceptional activity and stability for the oxidation of formic acid.

Highly Selective Activation of C-H Bond and Inhibition of C-C Bond Cleavage by Tuning Strong Oxidative Pd Sites.

Improving the product selectivity meanwhile restraining deep oxidation still remains a great challenge over the supported Pd-based catalysts. Herein, we demonstrate a universal strategy where the surface strong oxidative Pd sites are partially covered by the transition metal (e. g., Cu, Co, Ni, and Mn) oxide through thermal treatment of alloys. It could effectively inhibit the deep oxidation of isopropanol and achieve the ultrahigh selectivity (>98%) to the target product acetone in a wide temperature range of 50-200 °C, even at 150-200 °C with almost 100% isopropanol conversion over PdCu1.2/Al2O3, while an obvious decline in acetone selectivity is observed from 150 °C over Pd/Al2O3. Furthermore, it greatly improves the low-temperature catalytic activity (acetone formation rate at 110 °C over PdCu1.2/Al2O3, 34.1 times higher than that over Pd/Al2O3). The decrease of surface Pd site exposure weakens the cleavage for the C-C bond, while the introduction of proper CuO shifts the d-band center (εd) of Pd upward and strengthens the adsorption and activation of reactants, providing more reactive oxygen species, especially the key super oxygen species (O2-) for selective oxidation, and significantly reducing the barrier of O-H and ß-C-H bond scission. The molecular-level understanding of the C-H and C-C bond scission mechanism will guide the regulation of strong oxidative noble metal sites with relatively inert metal oxide for the other selective catalytic oxidation reactions.

Single-Cell Metabolomics-Based Strategy for Studying the Mechanisms of Drug Action.

Studying the mechanisms of drug antitumor activity at the single-cell level can provide information about the responses of cell subpopulations to drug therapy, which is essential for the accurate treatment of cancer. Due to the small size of single cells and the low contents of metabolites, metabolomics-based approaches to studying the mechanisms of drug action at the single-cell level are lacking. Herein, we develop a label-free platform for studying the mechanisms of drug action based on single-cell metabolomics (sMDA-scM) by integrating intact living-cell electro-launching ionization mass spectrometry (ILCEI-MS) with metabolomics analysis. Using this platform, we reveal that non-small-cell lung cancer (NSCLC) cells treated by gefitinib can be clustered into two cell subpopulations with different metabolic responses. The glutathione metabolic pathway of the subpopulation containing 14.4% of the cells is not significantly affected by gefitinib, exhibiting certain resistance characteristics. The presence of these cells masked the judgment of whether cysteine and methionine metabolic pathway was remarkably influenced in the analysis of overall average results, revealing the heterogeneity of the response of single NSCLC cells to gefitinib treatment. The findings provide a basis for evaluating the early therapeutic effects of clinical medicines and insights for overcoming drug resistance in NSCLC subpopulations.

Quantitative Analysis of Nanoplastics in Single Cells by Subcellular Chromatography.

The accumulation and spatial distribution of intracellular nanoplastic particles provide useful information about their spatiotemporal toxicological effects mediated by the physicochemical parameters of nanoplastics in living cells. In this study, a sample injection-transfer method was designed with an accuracy of up to femtoliters to attoliters to match the volume required for ultranarrow-bore open-tubular liquid chromatography. The separation and concentration quantification of mixed polystyrenes in different regions in living cells were achieved by directly transferring picoliter/femtoliter volumes of intracellular cytoplasm to an ultranarrow-bore open-tubular chromatographic column. The measurement of pollutant concentration in different areas of a small-volume target (single cell) was realized. This method is expected to be used in the qualitative and quantitative analyses of complex, mixed, and label-free nanoplastics (a few nm in size) in the subregions of living cells.

Sensitive electrochemical measurement of nitric oxide released from living cells based on dealloyed PtBi alloy nanoparticles.

Nitric oxide (NO), as a vital signaling molecule related to different physiological and pathological processes in living systems, is closely associated with cancer and cardiovascular disease. However, the detection of NO in real-time remains a difficulty. Here, PtBi alloy nanoparticles (NPs) were synthesized, dealloyed, and then fabricated to NP-based electrodes for the electrochemical detection of NO. Transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and nitrogen physical adsorption/desorption show that dealloyed PtBi alloy nanoparticles (dPtBi NPs) have a porous nanostructure. Electrochemical impedance spectroscopy and cyclic voltammetry results exhibit that the dPtBi NP electrode possesses unique electrocatalytic features such as low charge transfer resistance and large electrochemically active surface area, which lead to its excellent NO electrochemical sensing performance. Owing to the higher density of catalytical active sites formed PtBi bimetallic interface, the dPtBi NP electrode displays superior electrocatalytic activity toward the oxidation of NO with a peak potential at 0.74 V vs. SCE. The dPtBi NP electrode shows a wide dynamic range (0.09-31.5 µM) and a low detection limit of 1 nM (3σ/k) as well as high sensitivity (130 and 36.5 µA µM-1 cm-2). Moreover, the developed dPtBi NP-based electrochemical sensor also exhibited good reproducibility (RSD 5.7%) and repeatability (RSD 3.4%). The electrochemical sensor was successfully used for the sensitive detection of NO produced by live cells. This study indicates a highly effective approach for regulating the composition and nanostructures of metal alloy nanomaterials, which might provide new technical insights for developing high-performance NO-sensitive systems, and have important implications in enabling real-time detection of NO produced by live cells.

Determination of Nanoplastics Using a Novel Contactless Conductivity Detector with Controllable Geometric Parameters.

Plastic waste in the environment is continuously degraded to form nanoplastic particles, and its harm has attracted widespread attention. At present, the identification and quantification of nanoplastics are performed by visual observation and using some spectroscopy methods, which are time-consuming and lack accuracy. Therefore, this study proposes a contactless conductivity detector (C4D) based on a glass microfluidic chip with controllable geometric parameters to quantify nanoplastics. We found that when the insulating layer thickness was 15 µm, the electrode spacing was 1 mm, and the shielding method was on-chip shielding, the detector displayed the best performance. The detector possesses a simple structure with high sensitivity and outstanding reproducibility, that is, the limit of detection of KCl solutions can reach the micromolar level, and the intraday RSD is 0.2% (n = 5). This work uses a microfluidic chip C4D to study nanoplastics for the first time, and the limit of detection is 0.25 µg/mL and the quantitative limit is 0.8 µg/mL. In addition, plant experiments have verified that terrestrial plants can absorb nanoplastics in water, expanding the application of contactless conductivity detectors and providing a new method for the quantitative analysis of nanoplastics.

Controllable Fabrication of Small-Size Holding Pipets for the Nondestructive Manipulation of Suspended Living Single Cells.

The capture and manipulation of single cells are an important premise and basis for intracellular delivery, which provides abundant molecular and omics information for biomedical development. However, for intracellular delivery of cargos into/from small-size suspended living single cells, the capture methods are limited by the lack of small-size holding pipets, poor cell activity, and the low spatial accuracy of intracellular delivery. To solve these problems, a method for the controllable fabrication of small-size holding pipets was proposed. A simple, homemade microforge instrument including an imaging device was built to cut and melt the glass capillary tip by controlling the heat production of a nichrome wire. The controllable fabrication of small-size holding pipets was realized by observing the fabrication process in real time. Combined with an electroosmotic drive system and a micromanipulation system with high spatial resolution, the holding pipet achieved the active capture, movement, and sampling of suspended living single cells. Moreover, solid-phase microextraction was performed on captured single pheochromocytoma cells, and the extracted dopamine was successfully detected using an electrochemical method. The homemade microforge instrument overcame the limitations of traditional microforges, resulting in holding pipets that were sufficiently small for small-size suspended single living cells (5-30 µm). This proactive capture method overcame the shortcomings of existing methods to achieve the multiangle, high-precision manipulation of single cells, thereby allowing the intracellular delivery of small-size single cells in suspension with high spatiotemporal resolution.

Synergy in Au-CuO Janus Structure for Catalytic Isopropanol Oxidative Dehydrogenation to Acetone.

The controlled oxidation of alcohols to the corresponding ketones or aldehydes via selective cleavage of the ß-C-H bond of alcohols under mild conditions still remains a significant challenge. Although the metal/oxide interface is highly active and selective, the interfacial sites fall far behind the demand, due to the large and thick support. Herein, we successfully develop a unique Au-CuO Janus structure (average particle size=3.8 nm) with an ultrathin CuO layer (0.5 nm thickness) via a bimetal in situ activation and separation strategy. The resulting Au-CuO interfacial sites prominently enhance isopropanol adsorption and decrease the energy barrier of ß-C-H bond scission from 1.44 to 0.01 eV due to the strong affinity between the O atom of CuO and the H atom of isopropanol, compared with Au sites alone, thereby achieving ultrahigh acetone selectivity (99.3 %) over 1.1 wt % AuCu0.75 /Al2 O3 at 100 °C and atmospheric pressure with 97.5 % isopropanol conversion. Furthermore, Au-CuO Janus structures supported on SiO2 , TiO2 or CeO2 exhibit remarkable catalytic performance, and great promotion in activity and acetone selectivity is achieved as well for other reducible oxides derived from Fe, Co, Ni and Mn. This study should help to develop strategies for maximized interfacial site construction and structure optimization for efficient ß-C-H bond activation.

Aggregation-Induced Electrochemiluminescence of the Dichlorobis(1,10-phenanthroline)ruthenium(II) (Ru(phen)2Cl2)/Tri-n-propylamine (TPrA) System in H2O-MeCN Mixtures for Identification of Nucleic Acids.

Aggregation-induced electrochemiluminescence (AIECL) of the dichlorobis(1,10-phenanthroline)ruthenium(II) (Ru(phen)2Cl2)/tri-n-propylamine (TPrA) system was systematically investigated in H2O-MeCN media. Up to a 120-fold increase in the ECL intensity was observed when the H2O fraction (v%) was changed from 30% to 70%, whereas only an approximately 5.7-fold increase in the corresponding aggregation-induced fluorescence emission was demonstrated. The gradual formation of clusters of Ru(phen)2Cl2 nanoaggregates along with the increase in the H2O fraction to MeCN, which was verified by dynamic light scattering (DLS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), was believed to be responsible for the remarkable ECL enhancement. Significantly, the above-mentioned AIECL behavior was found to be very sensitive to the types and sequences of nucleic acids present in solution, which provided an effective and novel strategy for distinguishing RNA from DNA and for differentiating different miRNAs. The present study could have a substantial impact in various research areas, such as molecular sensors, bioimaging probes, organelle-specific imaging, and tumor diagnosis.

Electrogenerated Chemiluminescence Biosensor with a Tripod Probe for the Highly Sensitive Detection of MicroRNA.

A novel probe for the highly sensitive detection of microRNA with enhanced helix accessibility and good assembling without backfilling was developed using a tripod structure fabricated by triplex DNA. A layer of triplex DNA assembled on electrodeposited reduced graphene oxide was used as the capture probe, and a subsequent hybridization chain reaction that promoted the efficient intercalation of the electrogenerated chemiluminescence (ECL) emitter [Ru(bpy)2(dppz)]2+ (bpy refers to 2,2'-bipyridine, and dppz refers to dipyrido[3,2- a:2',3'- c]phenazine) was used as an analytical-signal amplifier. The fabricated biosensor was examined with an anodic ECL mode using tri- n-propyl amine as the coreactant. The construction of the biosensor was systematically characterized with various techniques including atomic-force microscopy, gel electrophoresis, cyclic voltammetry, and electrochemical-impedance spectroscopy, and its performance was optimized under a variety of experimental conditions, especially the concentration of each reagent as well as the incubation time. Under the optimal experimental conditions, the reported biosensor showed a very low limit of detection of 0.10 fM (S/N = 3) and a wide linear dynamic range covering 0.50 fM to 100 pM toward microRNA-155 with excellent specificity, stability, and reproducibility. Finally, the biosensor was successfully applied to the detection of microRNA-155 extracted from the colon-cancer cell line DLD1, demonstrating its potential application in the sensitive detection of biological samples in the early diagnosis of diseases.

In-tube solid-phase microextraction capillary column packed with mesoporous TiO2 nanoparticles for phosphopeptide analysis.

In this study, an in-tube solid-phase microextraction column packed with mesoporous TiO2 nanoparticles, coupled with MALDI-TOF-MS, was applied to the selective enrichment and detection of phosphopeptides in complex biological samples. The mesoporous TiO2 nanoparticles with high specific surface areas, prepared by a sol-gel and solvothermal method, were injected into the capillary using a slurry packing method with in situ polymerized monolithic segments as frits. Compared with the traditional solid-phase extraction method, the TiO2 -packed column with an effective length of 1 cm exhibited excellent selectivity (α-casein/ß-casein/BSA molar ratio of 1:1:100) and sensitivity (10 fmol of a ß-casein enzymatic hydrolysis sample) for the enrichment of phosphopeptides. These performance characteristics make this system suitable for the detection of phosphorylated peptides in practical biosamples, such as nonfat milk.

Enabling Colloidal Synthesis of Edge-Oriented MoS2 with Expanded Interlayer Spacing for Enhanced HER Catalysis.

By selectively promoting heterogeneous nucleation/growth of MoS2 on graphene monolayer sheets, edge-oriented (EO) MoS2 nanosheets with expanded interlayer spacing (∼9.4 Å) supported on reduced graphene oxide (rGO) sheets were successfully synthesized through colloidal chemistry, showing the promise in low-cost and large-scale production. The number and edge length of MoS2 nanosheets per area of graphene sheets were tuned by controlling the reaction time in the microwave-assisted solvothermal reduction of ammonium tetrathiomolybdate [(NH4)2MoS4] in dimethylformamide. The edge-oriented and interlayer-expanded (EO&IE) MoS2/rGO exhibited significantly improved catalytic activity toward hydrogen evolution reaction (HER) in terms of larger current density, lower Tafel slope, and lower charge transfer resistance compared to the corresponding interlayer-expanded MoS2 sheets without edge-oriented geometry, highlighting the importance of synergistic effect between edge-oriented geometry and interlayer expansion on determining HER activity of MoS2 nanosheets. Quantitative analysis clearly shows the linear dependence of current density on the edge length of MoS2 nanosheets.

Characterization of Brassinazole resistant (BZR) gene family and stress induced expression in Eucalyptus grandis.

Brassinosteroids (BRs) are a group of plant hormones which play a pivotal role in modulating cell elongation, stress responses, vascular differentiation and senescence. In response to BRs, BRASSINAZOLE-RESISTANT (BZR) transcription factors (TFs) accumulate in the nucleus, where they modulate thousands of target genes and coordinate many biological processes, especially in regulating defense against biotic and abiotic stresses. In this study, 6 BZR TFs of Eucalyptus grandis (EgrBZR) from a genome-wide survey were characterized by sequence analysis and expression profiling against several abiotic stresses. The results showed that BZR gene family in Eucalyptus was slightly smaller compared to Populus and Arabidopsis, but all phylogenetic groups were represented. Various systematic in silico analysis of these TFs validated the basic properties of BZRs, whereas comparative studies showed a high degree of similarity with recognized BZRs of other plant species. In the organ-specific expression analyses, 4 EgrBZRs were expressed in vascular tissue indicating their possible functions in wood formation. Meanwhile, almost all EgrBZR genes showed differential transcript abundance levels in response to exogenously applied BR, MeJA, and SA, and salt and cold stresses. Besides, protein interaction analysis showed that all EgrBZR genes were associated with BR signaling directly or indirectly. These TFs were proposed as transcriptional activators or repressors of abiotic stress response and growth and development pathways of E. grandis by participating in BR signaling processes. These findings would be helpful in resolving the regulatory mechanism of EgrBZRs in stress resistance conditions but require further functional study of these potential TFs in Eucalyptus.

Microfluidic Synthesis Enables Dense and Uniform Loading of Surfactant-Free PtSn Nanocrystals on Carbon Supports for Enhanced Ethanol Oxidation.

Developing new synthetic methods for carbon supported catalysts with improved performance is of fundamental importance in advancing proton exchange membrane fuel cell (PEMFC) technology. Continuous-flow, microfluidic reactions in capillary tube reactors are described, which are capable of synthesizing surfactant-free, ultrafine PtSn alloyed nanoparticles (NPs) on various carbon supports (for example, commercial carbon black particles, carbon nanotubes, and graphene sheets). The PtSn NPs are highly crystalline with sizes smaller than 2 nm, and they are highly dispersed on the carbon supports with high loadings up to 33 wt%. These characteristics make the as-synthesized carbon-supported PtSn NPs more efficient than state of the art commercial Pt/C catalysts applied to the ethanol oxidation reaction (EOR). Significantly enhanced mass catalytic activity (two-times that of Pt/C) and improved stability are obtained.

One-Step, Facile and Ultrafast Synthesis of Phase- and Size-Controlled Pt-Bi Intermetallic Nanocatalysts through Continuous-Flow Microfluidics.

Ordered intermetallic nanomaterials are of considerable interest for fuel cell applications because of their unique electronic and structural properties. The synthesis of intermetallic compounds generally requires the use of high temperatures and multiple-step processes. The development of techniques for rapid phase- and size-controlled synthesis remains a formidable challenge. The intermetallic compound Pt1Bi2 is a promising candidate catalyst for direct methanol fuel cells because of its high catalytic activity and excellent methanol tolerance. In this work, we explored a one-step, facile and ultrafast phase- and size-controlled process for synthesizing ordered Pt-Bi intermetallic nanoparticles (NPs) within seconds in microfluidic reactors. Single-phase Pt1Bi1 and Pt1Bi2 intermetallic NPs were prepared by tuning the reaction temperature, and size control was achieved by modifying the solvents and the length of the reaction channel. The as-prepared Pt-Bi intermetallic NPs exhibited excellent methanol tolerance capacity and high electrocatalytic activity. Other intermetallic nanomaterials, such as Pt3Fe intermetallic nanowires with a diameter of 8.6 nm and Pt1Sn1 intermetallic nanowires with a diameter of 6.3 nm, were also successfully synthesized using this method, thus demonstrating its feasibility and generality.

Ultralow Loading of Silver Nanoparticles on Mn2O3 Nanowires Derived with Molten Salts: A High-Efficiency Catalyst for the Oxidative Removal of Toluene.

Using a mixture of NaNO3 and NaF as molten salt and MnSO4 and AgNO3 as metal precursors, 0.13 wt % Ag/Mn2O3 nanowires (0.13Ag/Mn2O3-ms) were fabricated after calcination at 420 °C for 2 h. Compared to the counterparts derived via the impregnation and poly(vinyl alcohol)-protected reduction routes as well as the bulk Mn2O3-supported silver catalyst, 0.13Ag/Mn2O3-ms exhibited a much higher catalytic activity for toluene oxidation. At a toluene/oxygen molar ratio of 1/400 and a space velocity of 40,000 mL/(g h), toluene could be completely oxidized into CO2 and H2O at 220 °C over the 0.13Ag/Mn2O3-ms catalyst. Furthermore, the toluene consumption rate per gram of noble metal over 0.13Ag/Mn2O3-ms was dozens of times as high as that over the supported Au or AuPd alloy catalysts reported in our previous works. It is concluded that the excellent catalytic activity of 0.13Ag/Mn2O3-ms was associated with its high dispersion of silver nanoparticles on the surface of Mn2O3 nanowires and good low-temperature reducibility. Due to high efficiency, good stability, low cost, and convenient preparation, 0.13Ag/Mn2O3-ms is a promising catalyst for the practical removal of volatile organic compounds.

Substitution reactions in metal-organic frameworks and metal-organic polyhedra.

Substitution reaction, as one of the most powerful and efficient chemical reactions, has been widely used in various syntheses, including those for the design and preparation of functional molecules or materials. In the past decade, a class of newly developed inorganic-organic hybrid materials, namely metal-organic materials (MOMs), has experienced a rapid development. MOMs are composed of metal-containing nodes connected by organic linkers through strong chemical bonds, and can be divided into metal-organic frameworks (MOFs) and metal-organic polygons/polyhedra (MOPs) with infinite and discrete structural features, respectively. Recent research has shown that the substitution reaction can be used as a new strategy in the synthesis and modification of MOFs and MOPs, particularly for pre-designed ones with desired structures and functions, which are usually difficult to access by a direct one-pot self-assembly synthetic approach. This review highlights the implementation of the substitution reaction in MOFs and MOPs. Examples of substitution reactions at metal ions, organic ligands, and free guest molecules of MOFs and MOPs are listed and analyzed. The changes or modifications in the structures and/or properties of these materials induced by the substitutions, as well as the nature of the associated reaction, are discussed, with the conclusion that the substitution reaction is really feasible and powerful in synthesizing and tailoring MOMs.

Ruthenium-oxide-coated sodium vanadium fluorophosphate nanowires as high-power cathode materials for sodium-ion batteries.

Sodium-ion batteries are a very promising alternative to lithium-ion batteries because of their reliance on an abundant supply of sodium salts, environmental benignity, and low cost. However, the low rate capability and poor long-term stability still hinder their practical application. A cathode material, formed of RuO2 -coated Na3 V2 O2 (PO4 )2 F nanowires, has a 50 nm diameter with the space group of I4/mmm. When used as a cathode material for Na-ion batteries, a reversible capacity of 120 mAh g(-1) at 1 C and 95 mAh g(-1) at 20 C can be achieved after 1000 charge-discharge cycles. The ultrahigh rate capability and enhanced cycling stability are comparable with high performance lithium cathodes. Combining first principles computational investigation with experimental observations, the excellent performance can be attributed to the uniform and highly conductive RuO2 coating and the preferred growth of the (002) plane in the Na3 V2 O2 (PO4 )2 F nanowires.