EVQ-218: Characterization of High-Energy Nanoparticles that Measure up to NIST Standards.

EVQ-218 is a high-energy produced nanoparticle (NP) with a method of manufacture that avoids chemical or biological synthesis. The patented single-step process generates stable, pure metal NPs directly into HPLC grade water. Laser ablation via the multiple cross laser system occurs at a rate that is in the region of dielectric breakdown, generating temperatures and pressures akin to those of diamond formation. The spherical particles from this method have an ultrastable shell structure that inhibits the hallmark ion emission that occurs in other nanosilver species. The resulting particle size distribution is so narrow that additional size refinement or stabilizing chemistries are not necessary. These properties make EVQ-218 an attractive clean and green alternative to traditional nanosilvers, particularly when factoring in shelf life, as EVQ-218 maintains (uniform) stability for years, while NIST standard materials degrade within a few weeks. EVQ-218 characterization and differentiation are timely as the rise of antimicrobial resistance has caused a surge of research on antimicrobial silver NPs. It has been widely established that the antimicrobial activity of nanosilver is due to ion emission. Unfortunately, metal ions can be quite toxic and prevent certain biomedical and consumer product applications. In an ever-changing regulatory landscape, there is increasing scrutiny to definitively characterize nanomaterials and assess their potential environmental/toxicological footprint. EVQ-218 was characterized alongside comparable NIST standard NPs, with particular interest in speciation and fate. Particle characterization studies reveal that EVQ-218 is nearly equivalent to NIST standard material with respect to particle morphology and uniformity. Dissolution and surface chemistry studies quickly differentiate EVQ-218 as the first stable, nonemissive, pure metal NP that is on par with NIST standards for ideal materials.

Observation of magnetic ordering for layered (2-D) potassium diruthenium tetracarbonate, K3[Ru(II/III)2(O2CO)4]: a rare second row transition metal-based magnet.

The detailed magnetic behavior of K(3)[Ru(2)(CO(3))(4)].xH(2)O (x = 2) reveals that it has a 2-K magnetization at 5 T of 11 125 emu Oe/mol, a 50-Oe coercive field, and a remnant magnetization of 670 emu Oe/mol. It magnetically orders as a canted ferrimagnet below 4.2 K, and is a rare example of a magnetically ordered material based on a second row transition metal. The magnetic ordering confirms that the S not equal to 0 M(II) site that bridges the layers in previously reported H(x)K(1-x)M(II)-[Ru(II/III)(2)(CO(3))(4)](H(2)O)(y)(MeOH)(z) (M = Mn, Fe, Co, Ni, Cu, Mg) does not contribute to the magnetic behavior that leads to magnetic ordering.

Anomalous non-Prussian blue structures and magnetic ordering of K(2)Mn(II)[Mn(II)(CN)(6)] and Rb(2)Mn(II)[Mn(II)(CN)(6)].

The reaction of Mn(II) and KCN in aqueous and non-aqueous media leads to the isolation of three-dimensional (3-D) Prussian blue analogues, K(2)Mn[Mn(CN)(6)] (1a-d, 1e, respectively). Use of RbCN forms Rb(2)Mn[Mn(CN)(6)] (2). 1 and 2 are isomorphic {monoclinic, P2(1)/n: 1 [a = 10.1786(1) A, b = 7.4124(1) A, c = 6.9758(1) A, beta = 90.206(1)(o)]; 2 [a = 10.4101(1) A, b = 7.4492(1) A, c = 7.2132(1) A, beta = 90.072(1)(o)]}, with a small monoclinic distortion from the face centered cubic (fcc) structure that is typical of Prussian blue structured materials that was previously reported for K(2)Mn[Mn(CN)(6)]. Most notably the average Mn-N-C angles are 148.8 degrees and 153.3 degrees for 1 and 2, respectively, which are significantly reduced from linearity. This is attributed to the ionic nature of high spin Mn(II) accommodating a reduced M-CN-M' angle and minimizing void space. Compounds 1a,b have a sharp, strong nu(OH) band at 3628 cm(-1), while 1e lacks a nu(OH) absorption. The nu(OH) absorption in 1a,b is attributed to surface water, as use of D(2)O shifts the nu(OH) absorption to 2677 cm(-1), and that 1a-e are isostructural. Also, fcc Prussian blue-structured Cs(2)Mn[Mn(CN)(6)] (3) has been structurally [Fm3m: a = 10.6061(1) A] and magnetically characterized. The magnetic ordering temperature, T(c), increases as K(+) (41 K) > Rb(+) (34.6 K) > Cs(+) (21 K) for A(2)Mn[Mn(CN)(6)] in accord with the increasing deviation for linearity of the Mn-N-C linkages [148.8 (K(+)) > 153.3 (Rb(+)) > 180 degrees (Cs(+))], decreasing Mn(II)...Mn(II) separations [5.09 (K(+)) < 5.19 (Rb(+)) < 5.30 A (Cs(+))], and decreasing size of the cation (increasing electrostatic interactions). Hence, the bent cyanide bridges play a crucial role in the superexchange mechanism by increasing the coupling via shorter Mn(II)...Mn(II) separations, and perhaps enhanced overlap. In addition, the temperature dependent magnetic behavior of K(4)[Mn(II)(CN)(6)].3H(2)O is reported.

Diruthenium tetracarbonate trianion, [Ru(II/III)(2)(O(2)CO)(4)](3-), based molecule-based magnets: three-dimensional network structure and two-dimensional magnetic ordering.

H(x)K(1-x)M(II)[Ru(2)(CO(3))(4)](H(2)O)(y)(MeOH)(z) (M = Mn, Fe, Co, Ni, Mg) were synthesized from the reaction of M(II) and K(3)[Ru(2)(CO(3))(4)] in water and are isomorphous with an orthorhombic three-dimensional network structures based on mu(3)-CO(3)(2-) linkages to Ru(2) moieties forming layers and also to trans-M(II)(OH(2))(4) sites forming linked chains that connect the layers. They, as well as non-isomorphous M = Cu, magnetically order as canted ferrimagnets with T(c) = 4.4 +/- 1.0 K. The presence of S = 0 M(II) = Mg(II) has essentially no effect on T(c) suggesting that the main magnetic pathway does not occur the through M(II)-based chains, but only via Ru(2)...Ru(2) linkages that reside in layers. This is a rare example of a magnet based upon a second row transition metal.

Structure and magnetic ordering of KxH1-xNi(OH2)4[Ru2(CO3)4].zH2O.

K(x)H(1-x)Ni(OH2)4[Ru2(CO3)4].zH2O is a ferrimagnet (Tc = 4.3 K) formed from the reaction of K3[Ru(II/III)2(CO3)4] and Ni(II) in water. It possesses a new 3-D network structural motif composed of linked chains and mu3-CO3 linkages to both Ru and Ni sites. Each Ni(II) bonds to four oxygens and to two [Ru2(CO3)4]3- moieties in a cis manner, and four mu3-CO3 groups from each [Ru2(CO3)4](3-) have two oxygens bonding to the Ru2 moiety, forming the typical paddle-wheel core, and trans pairs of the third CO32- oxygen axially bonded to either another Ru2 or Ni(II).

Structural and magnetic properties of MCl2 (M = Fe, Mn, Co): acetonitrile solvates.

MIICl2 (M = Mn, Fe, Co) as their acetonitrile solvates were isolated, and their structural, spectroscopic, and magnetic properties were studied. MCl2(NCMe)2 (M = Fe, Mn) form 1-D chains of octahedral MII ions with four bridging chlorides and two axial MeCN's. The presence of an axial distortion for MFe causes a significant magnetic anisotropy that increases significantly below 150 K; however, chiav [=(chi parallel + 2chi perpendicular)/3] almost coincides with the value obtained on a polycrystalline sample. MnCl2(NCMe)2 is a paramagnet with a weak antiferromagnetic coupling. Annealing FeCl2(NCMe)2 at 55 degrees C forms the monosolvate of FeCl2(NCMe) composition in which two chains collapse into a double chain with formation of Fe-Cl bonding such that half of the mu-Cl's becomes mu3-Cl's. This material orders magnetically below Tc = 4.3 K. For M = Co, paramagnetic tetrahedral [CoCl3(NCMe)]- anions are isolated.