Eye-safe UV stand-off Raman spectroscopy for the ranged detection of explosives in the field

Increasing worldwide terrorist attacks involving explosives presents a growing need for a rapid and ranged explosive detection method that can safely be deployed in the field. Stand-off Raman spectroscopy shows great promise; however, the radiant exposures of lasers required for adequate signal generation are often much greater than what is safe for the eye or the skin, restricting use of the technique to un-populated areas. Here, by determining the safe exposure levels for lasers typically used in Raman spectroscopy, optimal parameter values are identified, which produce the largest possible detection range using power densities that do not exceed the eye-safe limit. It is shown that safe ultraviolet pulse energies can be more than three orders of magnitude greater than equivalent safe visible pulse energies. Coupling this to the 16-fold increase in Raman signal obtained in the ultraviolet at 266 nm over that at 532 nm results in a 131 times larger detection range for the eye-safe 266-nm system over an equivalent eye-safe 532-nm laser system. For the Raman system described here, this translates to a maximum range of 42 m for detecting Teflon with a 266-nm laser emitting a 100-mm diameter beam of 23.5-mJ nanosecond pulses.

Crystal structure of poly[[di-mu2-aqua-aquasodium] 4-amino-3,5,6-trichloropyridine-2-carboxylate trihydrate], the sodium salt of the herbicide picloram

In the structure of the title complex [[Na(H2O)3]+ (C6H2Cl3N2O2)-^ . 3(H2O)]n, the Na salt of the herbicide picloram, the cation is a polymeric chain structure, based on doubly water-bridged NaO5 trigonal bipyramidal complex units which have in addition, a singly-bonded monodentate water molecule. Each of the bridges within the chain which lies along the a cell direction is centrosymmetric with Na...Na separations of 3.4807(16) and 3.5109(16)Ang. In the crystal, there are three water molecules of solvation and these, as well as the coordinated water molecules and the amino group of the 4-amino-3,5,6-trichloropicolinate anion are involved in extensive inter-species hydrogen-bonding interactions with carboxyl and water O-atoms as well as the pyridine N-atom. Among these association is a centrosymmetric cyclic tetra-water R4/4(8) ring , resulting in an overall three-dimensional structure.

Crystal structure of ammonium (3,5-dichlorophenoxy)acetate hemihydrate

In the structure of the title hydrated salt, NH4+·C8H5Cl2O3-·0.5H2O, where the anion derives from (3,5-di­chloro­phen­oxy)acetic acid, the ammonium cation is involved in extensive N-H...O hydrogen bonding with both carboxyl­ate and ether O-atom acceptors giving sheet structures lying parallel to (100). The water mol­ecule of solvation lies on a crystallographic twofold rotation axis and is involved in intra-sheet O-H...Ocarboxyl­ate hydrogen-bonding inter­actions. In the anion, the oxoacetate side chain assumes an antiperiplanar conformation with the defining C-O-C-C torsion angle = -171.33 (15)°.

Crystal structures of the potassium and rubidium salts of (3,5-dichlorophenoxy)acetic acid: Two isotypic coordination polymers

The two-dimensional coordination polymeric structures of the hydrated potassium and rubidium salts of (3,5-dichlorophenoxy)acetic acid, (3,5-D) namely, poly[mu-aqua-bis[mu3-2-(3,5-dichlorophenoxy)acetato]potassium, [K2(C8H5Cl2O3)2 (H2O)]n (I) and poly[mu-aqua-bis[mu3-2-(3,5-dichlorophenoxy)acetato]dirubidium] [Rb2(C8H5Cl2O3)2 (H2O)]n (II), respectively have been determined and are described. The two compounds are isotypic and the polymer is based on centrosymmetric dinuclear bridged complex units. The irregular six-coordination about the metal centres comprises a bridging water molecule lying on a twofold rotation axis, the phenoxy O-atom donor and and a triple bridging carboxylate O-atom of the oxoacetate side chain of the 3,5-D ligand in a bidentate chelate mode, the second carboxy O-donor, also bridging. The K-O and Rb-O bond-length ranges are 2.7238(15)--2.9459(14) and 2.832(2)--3.050(2) \%A respectively and the K...K and Rb...Rb separations in the dinuclear unit are 4.0214(7) and 4.1289(6) \%A, respectively. Within the two-dimensional layers which lie parallel to (100), the coordinated water molecule forms an O---H...O hydrogen bond to the single bridging carboxylate O atom.

Genetic factors in the pathogenesis of CPPD crystal deposition disease

Crystal deposition is a very complex process ruled by numerous factors. A small but important proportion of cases of chondrocalcinosis are monogenic, and many of the genes involved have been identified. These genetic findings strongly point to control of the level of extracellular inorganic pyrophosphate as the primary mechanism for their association with either calcium pyrophosphate dihydrate or hydroxyapatite deposition. However, effects on extracellular inorganic pyrophosphate levels do not explain the mechanism of association in all of these monogenic diseases. Further, there are likely to be several as yet unidentified genes that are important in this common condition. This review highlights what genetic studies have demonstrated about the processes involved in these diverse but related disorders.

Trace vapour detection at room temperature using Raman spectroscopy

A miniaturized flow-through system consisting of a gold coated silicon substrate based on enhanced Raman spectroscopy has been used to study the detection of vapour from model explosive compounds. The measurements show that the detectability of the vapour molecules at room temperature depends sensitively on the interaction between the molecule and the substrate. The results highlight the capability of a flow system combined with Raman spectroscopy for detecting low vapour pressure compounds with a limit of detection of 0.2 ppb as demonstrated by the detection of bis(2-ethylhexyl)phthalate, a common polymer additive emitted from a commercial polyvinyl chloride (PVC) tubing at room temperature.

Raman spectroscopy techniques for detection of energetic materials at high and low concentration

This thesis presents the development of a rapid, sensitive and reproducible spectroscopic method for the detection of TNT in forensic and environmental applications. Simple nano sensors prepared by cost effective methods were utilized as sensitive platforms for the detection of TNT by surface enhanced Raman spectroscopy. The optimization of the substrate and the careful selection of a suitable recognition molecule contributed to the significant improvements of sensitive and selective targeting over current detection methods. The work presented in this thesis paves the way for effective detection and monitoring of explosives residues in law enforcement and environmental health applications.

Crystal structures of the endoplasmic reticulum aminopeptidase-1 (ERAP1) reveal the molecular basis for N-terminal peptide trimming

Endoplasmatic reticulum aminopeptidase 1 (ERAP1) is a multifunctional enzyme involved in trimming of peptides to an optimal length for presentation by major histocompatibility complex (MHC) class I molecules. Polymorphisms in ERAP1 have been associated with chronic inflammatory diseases, including ankylosing spondylitis (AS) and psoriasis, and subsequent in vitro enzyme studies suggest distinct catalytic properties of ERAP1 variants. To understand structure-activity relationships of this enzyme we determined crystal structures in open and closed states of human ERAP1, which provide the first snapshots along a catalytic path. ERAP1 is a zinc-metallopeptidase with typical H-E-X-X-H-(X)18-E zinc binding and G-A-M-E-N motifs characteristic for members of the gluzincin protease family. The structures reveal extensive domain movements, including an active site closure as well as three different open conformations, thus providing insights into the catalytic cycle. A K 528R mutant strongly associated with AS in GWAS studies shows significantly altered peptide processing characteristics, which are possibly related to impaired interdomain interactions.

Genetic studies of disorders of calcium crystal deposition

In summary, although many factors are likely to be involved in regulating calcification and ossification processes, studies of the causation of articular chondrocalcinosis and disorders of spinal ossification, such as DISH and OPLL, implicate control over inorganic pyrophosphate levels as being one of the most important factors in their aetiopathogenesis. The findings of these studies may prove relevant to other rheumatic diseases in which ectopic ossification occurs, such as AS.

Crystal structures and hydrogen bonding in the morpholinium salts of four phenoxyacetic acid analogues

The anhydrous salts morpholinium (tetrahydro-2-H-1,4-oxazine) phenxyacetate, C4H10NO+ C8H7O3- (I), (4-fluorophenoxy)acetate, C4H10NO+ C8H6FO3- (II) and isomeric morpholinium (3,5-dichlorophenoxy)acetate (3,5-D) (III) and morpholinium (2,4-dichlorophenoxy)acetate (2,4-D), C4H10NO+ C8H5Cl2O3- (IV), have been determined and their hydrogen-bonded structures are described. In the crystals of (I), (III) and (IV), one of the the aminium H atoms is involved in a three-centre asymmetric cation-anion N-H...O,O' R2/1(4) hydrogen-bonding interaction with the two carboxyl O-atom acceptors of the anion. With the structure of (II), the primary N---H...O interaction is linear. In the structures of (I), (II) and (III), the second N-H...O(carboxyl) hydrogen bond generates one-dimensional chain structures extending in all cases along [100]. With (IV), the ion pairs are linked though inversion-related N-H...O hydrogen bonds [graph set R2/4(8)], giving a cyclic heterotetrameric structure.

Crystal structure of morpholin-4-ium cinnamate

In the anhydrous salt formed from the reaction of morpholine with cinnamic acid, C4H10NO+ C9H7O2-, the acid side chain in the trans-cinnamate anion is significantly rotated out of the benzene plane [C-C-C-C torsion angle = 158.54(17)deg. In the crystal, one of the the aminium H atoms is involved in a asymmetric three-centre cation-anion N-H...(O,O') R2/1(4) hydrogen-bonding interaction with the two carboxyl O-atom acceptors of the anion. The second aminium H atom forms an inter-species N-H...O(carboxyl) hydrogen bond, generating a one-dimensional chain structure extending along [100]. Chains are linked by C-H...O interactions forming a supramolecular layer parallel to (01-1).

Crystal engineering in two dimensions: An approach to molecular nanopatterning

We describe a surprising cooperative adsorption process observed by scanning tunneling microscopy (STM) at the liquid−solid interface. The process involves the association of a threefold hydrogen-bonding unit, trimesic acid (TMA), with straight-chain aliphatic alcohols of varying length (from C7 to C30), which coadsorb on highly oriented pyrolytic graphite (HOPG) to form linear patterns. In certain cases, the known TMA “flower pattern” can coexist temporarily with the linear TMA−alcohol patterns, but it eventually disappears. Time-lapsed STM imaging shows that the evolution of the flower pattern is a classical ripening phenomenon. The periodicity of the linear TMA−alcohol patterns can be modulated by choosing alcohols with appropriate chain lengths, and the precise structure of the patterns depends on the parity of the carbon count in the alkyl chain. Interactions that lead to this odd−even effect are analyzed in detail. The molecular components of the patterns are achiral, yet their association by hydrogen bonding leads to the formation of enantiomeric domains on the surface. The interrelation of these domains and the observation of superperiodic structures (moiré patterns) are rationalized by considering interactions with the underlying graphite surface and within the two-dimensional crystal of the adsorbed molecules. Comparison of the observed two-dimensional structures with the three-dimensional crystal structures of TMA−alcohol complexes determined by X-ray crystallography helps reveal the mechanism of molecular association in these two-component systems.

Rapid isolation and detection of erythropoietin in blood plasma by magnetic core gold nanoparticles and portable Raman spectroscopy

Isolating, purifying, and identifying proteins in complex biological matrices is often difficult, time consuming, and unreliable. Herein we describe a rapid screening technique for proteins in biological matrices that combines selective protein isolation with direct surface enhanced Raman spectroscopy (SERS) detection. Magnetic core gold nanoparticles were synthesised, characterised, and subsequently functionalized with recombinant human erythropoietin (rHuEPO)-specific antibody. The functionalized nanoparticles were used to capture rHuEPO from horse blood plasma within 15 minutes. The selective binding between the protein and the functionalized nanoparticles was monitored by SERS. The purified protein was then released from the nanoparticles’ surface and directly spectroscopically identified on a commercial nanopillar SERS substrate. ELISA independently confirmed the SERS identification and quantified the released rHuEPO. Finally, the direct SERS detection of the extracted protein was successfully demonstrated for in-field screening by a handheld Raman spectrometer within 1 minute sample measurement time.

Performance modulation of α-MnO2 nanowires by crystal facet engineering

Modulation of material physical and chemical properties through selective surface engineering is currently one of the most active research fields, aimed at optimizing functional performance for applications. The activity of exposed crystal planes determines the catalytic, sensory, photocatalytic, and electrochemical behavior of a material. In the research on nanomagnets, it opens up new perspectives in the fields of nanoelectronics, spintronics, and quantum computation. Herein, we demonstrate controllable magnetic modulation of α-MnO 2 nanowires, which displayed surface ferromagnetism or antiferromagnetism, depending on the exposed plane. First-principles density functional theory calculations confirm that both Mn- and O-terminated α-MnO2(1 1 0) surfaces exhibit ferromagnetic ordering. The investigation of surface-controlled magnetic particles will lead to significant progress in our fundamental understanding of functional aspects of magnetism on the nanoscale, facilitating rational design of nanomagnets. Moreover, we approved that the facet engineering pave the way on designing semiconductors possessing unique properties for novel energy applications, owing to that the bandgap and the electronic transport of the semiconductor can be tailored via exposed surface modulations.