Highly Specific Non-Enzymatic Electrochemical Sensor for the Detection of Uric Acid Using Carboxylated Multiwalled Carbon Nanotubes Intertwined with GdS-GdO Nanoplates in Human Urine and Serum.

Herein, the electrochemical sensing efficacy of carboxylic acid functionalized multiwalled carbon nanotubes (C-MWCNT) intertwined with coexisting phases of gadolinium monosulfide (GdS) and gadolinium oxide (GdO) nanosheets is explored for the first time. The nanocomposite demonstrated splendid specificity for nonenzymatic electrochemical detection of uric acid (UA) in biological samples. It was synthesized using the coprecipitation method and thoroughly characterized.

Light-induced spin-state switching in Fe(II) spin-crossover complexes with thiazole-based chelating ligands.

Homoleptic complexes [Fe(4bt)](ClO) (1), [Fe(2bt)](ClO) (2), and [Fe(3tpH)](ClO) (3) were obtained by a reaction between the Fe(II) precursor salt and the corresponding thiazole-based bidentate ligand (L = 4bt = 4,4'-bithiazole, 2bt = 2,2'-bithiazole, 3tpH = 3-(thiazol-2-yl)pyrazole). X-ray crystal structure determination revealed crystallization of solvent-free complex 1, a solvate 2·MeOH, and a co-crystal 3·2(3tpH). The crystal packing of all these complexes is dominated by one-dimensional interactions between the [Fe(L)] cations.

Combined Experimental and Mechanoelastic Modeling Studies on the Low-Spin Stabilized Mixed Crystals of 3D Oxalate-Based Coordination Materials.

Structural studies involving single-crystal and powder X-ray diffraction analysis have been performed on dehydrated coordination networks of the [NiCo(bpy)][LiCr(ox)] series, 0 ≤ ≤ 1, (bpy = 2,2'-bipyridine). The high-symmetry cubic 3D structure of these materials is formed by oxalate anions bridging alternating Cr and Li ions into an anionic framework, which contains large cavities that incorporate the [NiCo(bpy)] cations. Irrespective of the Co/Ni ratio, all of the mixed samples are phase-pure and retain the high-symmetry cubic structure, with the lattice parameters gradually decreasing upon increasing Ni(II) concentration.

Trend in light-induced excited-state spin trapping in Fe(II)-based spin crossover systems.

A computational study of the light-induced excited spin-state trapping (LIESST) in a number of Fe(II) spin crossover complexes, coordinated by monodentate, bidentate and multidentate ligands is carried out, with the goal to uncover the trend in the low temperature relaxation rate. A nine order of magnitude change in low temperature relaxation rate is observed among the complexes. The trend is rationalized in terms of the change in metal-ligand covalency, numerically estimated by the crystal orbital Hamiltonian population, thus influencing the back donation or delocalization of the electrons from the low-lying Fe(II)-centered molecular orbital to the empty low-lying ligand-centered π* antibonding molecular orbitals.

Optical microscopy imaging of the thermally-induced spin transition and isothermal multi-stepped relaxation in a low-spin stabilized spin-crossover material.

The thermal spin transition and the photo-induced high-spin → low-spin relaxation of the prototypical [Fe(ptz)](BF) spin-crossover compound (ptz = 1-propyltetrazole) diluted in the isostructural ruthenium host lattice [Ru(ptz)](BF), which stabilizes the Fe(II) low-spin state, have been investigated. We demonstrate the presence of a crystallographic phase transition around 145 K ( from the high-temperature ordered high-spin phase to a low-temperature disordered low-spin phase) upon slow cooling from room temperature. This crystallographic phase transition is decoupled from the thermal spin transition.

Kinetics of Isovalent (Cd) and Aliovalent (In) Cation Exchange in CdMnSe Nanocrystals.

Ion exchange, in which an in-diffusing ion replaces a lattice ion, has been widely exploited as a synthetic tool for semiconductor doping and solid-to-solid chemical transformations, both in bulk and at the nanoscale. Here, we present a systematic investigation of cation-exchange reactions that involve the displacement of Mn from CdSe nanocrystals by Cd or In. For both incoming cations, Mn displacement is spontaneous but thermally activated, following Arrhenius behavior over a broad experimental temperature range.

Tuning Equilibrium Compositions in Colloidal Cd1-xMnxSe Nanocrystals Using Diffusion Doping and Cation Exchange.

The physical properties of semiconductor nanocrystals can be tuned dramatically via composition control. Here, we report a detailed investigation of the synthesis of high-quality colloidal Cd1-xMnxSe nanocrystals by diffusion doping of preformed CdSe nanocrystals. Until recently, Cd1-xMnxSe nanocrystals proved elusive because of kinetic incompatibilities between Mn(2+) and Cd(2+) chemistries.

Light-induced spin-state switching in the mixed crystal series of the 2D coordination network {[Zn1-xFex(bbtr)3](BF4)2}∞: optical spectroscopy and cooperative effects.

Depending on the iron(ii) concentration, the mixed crystals of {[Zn1-xFex(bbtr)3](BF4)2}∞, bbtr = 1,4-di(1,2,3-triazol-1-yl)butane, 0.01 ≤ x ≤ 1, show macroscopic light-induced bistability between the high-spin and the low-spin state. In the highly diluted system with x = 0.

The role of ligand-field states in the ultrafast photophysical cycle of the prototypical iron(II) spin-crossover compound [Fe(ptz)(6)](BF(4))(2).

Light-induced excited spin-state trapping (LIESST) in iron(II) spin-crossover compounds, that is, the light-induced population of the high-spin (S=2) state below the thermal transition temperature, was discovered thirty years ago. For irradiation into metal-ligand charge transfer (MLCT) bands of the low-spin (S=0) species the acknowledged sequence takes the system from the initially excited (1) MLCT to the high-spin state via the (3) MLCT state within ca. 150 fs, thereby bypassing low-lying ligand-field (LF) states.

Light-induced bistability in the 2 D coordination network {[Fe(bbtr)3][BF4]2}∞ : wavelength-selective addressing of molecular spin states.

Whereas the neat polymeric Fe(II) compound {[Fe(bbtr)3 ][ClO4 ]2 }∞ (bbtr=1,4-di(1,2,3-triazol-1-yl)butane) shows an abrupt spin transition centered at 107 K facilitated by a crystallographic symmetry breaking, in the covalently linked 2D coordination network of {[Fe(bbtr)3 ][BF4 ]2 }∞ , Fe(II) stays in the high-spin state down to 10 K. However, strong cooperative effects of elastic origin result in reversible, persistent, and wavelength-selective photoswitching between the low-spin and high-spin manifolds. This compound thus shows true light-induced bistability below 100 K.

Heteroleptic Fe(II) complexes of 2,2'-biimidazole and its alkylated derivatives: spin-crossover and photomagnetic behavior.

Three iron(II) complexes, [Fe(TPMA)(BIM)](ClO(4))(2)⋅0.5H(2)O (1), [Fe(TPMA)(XBIM)](ClO(4))(2) (2), and [Fe(TPMA)(XBBIM)](ClO(4))(2)⋅0.75CH(3)OH (3), were prepared by reactions of Fe(II) perchlorate and the corresponding ligands (TPMA=tris(2-pyridylmethyl)amine, BIM=2,2'-biimidazole, XBIM=1,1'-(α,α'-o-xylyl)-2,2'-biimidazole, XBBIM=1,1'-(α,α'-o-xylyl)-2,2'-bibenzimidazole).

Thermal and light-induced spin switching dynamics in the 2D coordination network of {[Zn(1-x)Fe(x)(bbtr)3](ClO4)2}∞: the role of cooperative effects.

The thermal spin transition, the photoexcitation, and the subsequent spin relaxation in the mixed crystal series of the covalently linked two-dimensional network {[Zn(1-x)Fe(x)(bbtr)(3)](ClO(4))(2)}(∞) (x = 0.02-1, bbtr =1,4-di(1,2,3-triazol-1-yl)-butane) are discussed. In the neat compound, the thermal spin transition with a hysteresis of 13 K is accompanied by a crystallographic phase transition (Kusz, J.

Persistent bidirectional optical switching in the 2D high-spin polymer {[Fe(bbtr)3](BF4)2}∞.

In the covalently linked 2D coordination network {[Fe(bbtr)(3)](BF(4))(2)}(∞), bbtr = 1,4-di(1,2,3-triazol-1-yl)butane, the iron(II) centers stay in the high-spin (HS) state down to 10 K. They can, however, be quantitatively converted to the low-spin (LS) state by irradiating into the near-IR spin allowed (5)dd band and back again by irradiating into the visible (1)dd band. The compound shows true light-induced bistability below 100 K, thus, having the potential for persistent bidirectional optical switching at elevated temperatures.

Low-spin→high-spin relaxation dynamics in the highly diluted spin-crossover system [Fe(x)Zn(1-x)(bbtr)3](ClO4)2.

Whereas the neat polymeric iron(II) compound [Fe(bbtr)(3)](ClO(4))(2), bbtr = 1,4-di(1,2,3-triazol-1-yl)butane, shows a quantitative spin transition triggered by a crystallographic phase transition centered at 107 K with a 13 K wide hysteresis, the iron(II) complexes in the diluted mixed crystals [Fe(x)Zn(1-x)(bbtr)(3)](ClO(4))(2), x = 0.02 and 0.1, stay predominantly in the (5)T(2) high-spin state down to cryogenic temperatures.

Organization of nucleobase-functionalized beta-peptides investigated by soft electrospray ionization mass spectrometry.

The development and validation of analytical methods is a key to succeed in investigating noncovalent interactions between biomolecules or between small molecules and biomolecules. Electrospray ionization mass spectrometry (ESI-MS) was applied with a Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS) as well as a quadrupole/time-of-flight tandem mass spectrometer (QqToF-MS) for a systematic investigation of noncovalent complexes based on nucleobase pairing in an artificial and noncharged backbone topology. Synthetical beta-peptide helices covalently modified with nucleobases were organized by recognition of a sequence of four nucleobases.

Three-dimensional organization of helices: design principles for nucleobase-functionalized beta-peptides.

The construction and molecular recognition of various three-dimensional biomimetic structures is based on the predictable de novo design of artificial molecules. In this regard beta-peptides are especially interesting, since stable secondary structures are obtained already with short sequences; one of them is the 14-helix in which every third residue has the same orientation. The covalent functionalization of every third 14-helix side chain with nucleobases was used for a reversible organization of two helices based on nucleobase pairing.