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1.
Inorg Chem ; 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-32196322

RESUMO

Spin-phonon coupling plays a critical role in magnetic relaxation in single-molecule magnets (SMMs) and molecular qubits. Yet, few studies of its nature have been conducted. Phonons here refer to both intermolecular and intramolecular vibrations. In the current work, we show spin-phonon couplings between IR-active phonons in a lanthanide molecular complex and Kramers doublets (from the crystal field). For the SMM Er[N(SiMe3)2]3 (1, Me = methyl), the couplings are observed in the far-IR magnetospectroscopy (FIRMS) of crystals with coupling constants ≈ 2-3 cm-1. In particular, one of the magnetic excitations couples to at least two phonon excitations. The FIRMS reveals at least three magnetic excitations (within the 4I15/2 ground state/manifold; hereafter, manifold) at 0 T at 104, ∼180, and 245 cm-1, corresponding to transitions from the ground state, MJ = ±15/2, to the first three excited states, MJ = ±13/2, ±11/2, and ±9/2, respectively. The transition between the ground and first excited Kramers doublet in 1 is also observed in inelastic neutron scattering (INS) spectroscopy, moving to a higher energy with an increasing magnetic field. INS also gives complete phonon spectra of 1. Periodic DFT computations provide the energies of all phonon excitations, which compare well with the spectra from INS, supporting the assignment of the inter-Kramers doublet (magnetic) transitions in the spectra. The current studies unveil and measure the spin-phonon couplings in a typical lanthanide complex and throw light on the origin of the spin-phonon entanglement.

2.
Chemistry ; 25(69): 15846-15857, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31529652

RESUMO

Large separations between ground and excited magnetic states in single-molecule magnets (SMMs) are desirable to reduce the likelihood of spin reversal in the molecules. Spin-phonon coupling is a process leading to magnetic relaxation. Both the reversal and coupling, making SMMs lose magnetic moments, are undesirable. However, direct determination of large magnetic states separations (>45 cm-1 ) is challenging, and few detailed investigations of the spin-phonon coupling have been conducted. The magnetic separation in [Co(12-crown-4)2 ](I3 )2 (12-crown-4) (1) is determined and its spin-phonon coupling is probed by inelastic neutron scattering (INS) and far-IR spectroscopy. INS, using oriented single crystals, shows a magnetic transition at 49.4(1.0) cm-1 . Far-IR reveals that the magnetic transition and nearby phonons are coupled, a rarely observed phenomenon, with spin-phonon coupling constants of 1.7-2.5 cm-1 . The current work spectroscopically determines the ground-excited magnetic states separation in an SMM and quantifies its spin-phonon coupling, shedding light on the process causing magnetic relaxation.

3.
Inorg Chem ; 58(19): 12555-12564, 2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31553166

RESUMO

Two mononuclear tetrahedral Co(II) complexes (HNEt3)2[Co(L1)2]·H2O (1) and (Bu4N)2[Co(L2)2]·H2O (2) (H2L1 = N,N'-bis(p-toluenesulfony1)oxamide, H2L2 = N,N'-diphenyloxamide) have been synthesized, and their structures have been characterized by single-crystal X-ray diffraction. Both complexes adopt distorted tetrahedral coordination geometries surrounding the Co(II) center, which is ligated by two doubly deprotonated oxamide ligands oriented perpendicularly to each other. Their axial magnetic anisotropies were revealed by the direct current (dc) magnetic measurements, high-field and high-frequency electron paramagnetic resonance, and theoretical calculations. Both complexes display slow magnetic relaxation in the absence of an applied dc field. Upon the application of the 0.15 T dc field, the quantum tunneling of magnetization is efficiently suppressed. In addition, both complexes display hysteresis loops with different field sweep rates at 1.8 K, which is rarely observed for Co(II) single-ion magnets (SIMs).

4.
Dalton Trans ; 48(28): 10743-10752, 2019 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-31250855

RESUMO

Three mononuclear six-coordinate Co(ii)-pseudohalide complexes [Co(L)X2] with two N-donor pseudohalido coligands occupying the cis-positions (X = NCS- (1), NCSe- (2) or N(CN)2- (3)), and a five-coordinate complex [Co(L)(NCO)][B(C6H5)4] (4) [L = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane (12-TMC)] have been prepared and structurally characterized. Easy-plane magnetic anisotropy for 1-3 and easy-axis anisotropy for 4 were revealed via the analyses of the direct-current magnetic data, high-frequency and -field EPR (HFEPR) spectra and ab initio theoretical calculations. They display slow magnetic relaxations under an external applied dc field. Typically, two slow relaxation processes were found in 1 and 2 while only one relaxation process occurs in 3 and 4. The Raman-like mechanism is found to be dominant in the studied temperature range in 1. For 2-4, the Raman process is dominant in the low temperature region, while the Orbach mechanism dominates in the high temperature range.

5.
Inorg Chem ; 57(21): 13618-13630, 2018 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-30335996

RESUMO

Dinuclear Cu(I) complexes bearing hexadentate, macrocyclic N-heterocyclic carbene (NHC) ligands, [Cu2(L1)(CH3CN)][PF6]2 (1) and [Cu2(L2)(CH3CN)]2[Cu2(L2)(CH3CN)2][PF6]6 (2), have been synthesized by the reactions of [H4L][PF6]4 (L = L1, L2) with excess Cu2O in acetonitrile. Crystallizations of the heat-treated samples of 1 and 2 from acetone/methanol/ether or CH3NO2/ether result in [Cu2(L1)][PF6]2 (3) and [Cu2(L2)][PF6]2 (4). Complexes 1-4 are emissive with luminescent maxima at 464, 472, 540, and 488 nm in the solid state, respectively. The origin of the red shift of the emission maximum of 3 relative to the other three complexes has been studied by theoretical calculations, showing the cuprophilic interactions in the excited state of 3. The mechanochromic luminescent properties of 1-4 have been studied. After grinding in a mortar, a significant emission color change is found with a red shift of 98 nm for 1, 82 nm for 2, 20 nm for 3, and 64 nm for 4, respectively. These mechanochromic transformations are found to be a crystalline-to-amorphous conversion, which can be reverted by adding drops of the organic solvent or recrystallization. The possible correlations between the luminescent properties and structural modifications such as Cu···Cu distances are discussed.

6.
Phys Chem Chem Phys ; 20(32): 21119-21126, 2018 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-30079409

RESUMO

Molecular dynamics is a fundamental property of metal complexes. These dynamic processes, especially for paramagnetic complexes under external magnetic fields, are in general not well understood. Quasielastic neutron scattering (QENS) in 0-4 T magnetic fields has been used to study the dynamics of Co(acac)2(D2O)2 (1-d4, acac = acetylacetonate). At 80-100 K, rotation of the methyl groups on the acac ligands is the dominant dynamical process. This rotation is slowed down by the magnetic field increase. Rotation times at 80 K are 5.6(3) × 10-10 s at 0 T and 2.04(10) × 10-9 s at 4 T. The QENS studies suggest that methyl groups in these paramagnetic Co(ii) molecules do not behave as isolated units, which is consistent with results from earlier magnetic susceptibility studies indicating the presence of intermolecular interactions. DFT calculations show that unpaired electron spin density in 1 is dispersed to the atoms of both acac and H2O ligands. Methyl torsions in 1-d4 have also been observed at 5-100 K in inelastic neutron spectroscopy (INS). The QENS and INS results here help understand the dynamics of the compound in the solid state.

7.
Nat Commun ; 9(1): 2572, 2018 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-29968702

RESUMO

Spin-phonon coupling plays an important role in single-molecule magnets and molecular qubits. However, there have been few detailed studies of its nature. Here, we show for the first time distinct couplings of g phonons of CoII(acac)2(H2O)2 (acac = acetylacetonate) and its deuterated analogs with zero-field-split, excited magnetic/spin levels (Kramers doublet (KD)) of the S = 3/2 electronic ground state. The couplings are observed as avoided crossings in magnetic-field-dependent Raman spectra with coupling constants of 1-2 cm-1. Far-IR spectra reveal the magnetic-dipole-allowed, inter-KD transition, shifting to higher energy with increasing field. Density functional theory calculations are used to rationalize energies and symmetries of the phonons. A vibronic coupling model, supported by electronic structure calculations, is proposed to rationalize the behavior of the coupled Raman peaks. This work spectroscopically reveals and quantitates the spin-phonon couplings in typical transition metal complexes and sheds light on the origin of the spin-phonon entanglement.

8.
Dalton Trans ; 47(30): 10162-10171, 2018 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-30010170

RESUMO

Experimental and theoretical studies of magnetic anisotropy and relaxation behavior of six-coordinate tris(pivalato)-Co(ii) and -Ni(ii) complexes (NBu4)[M(piv)3] (piv = pivalate, M = Co, 1; M = Ni, 2), with a coordination configuration at the intermediate between an octahedron and a trigonal prism, are reported. Direct current magnetic data and high-frequency and -field EPR spectra (HFEPR) of 1 have been modeled by a general Hamiltonian considering the first-order orbital angular momentum, while the spin Hamiltonian was used to interpret the data of 2. Both 1 and 2 show easy-axis magnetic anisotropies, which are further supported by ab initio calculations. Alternating current (ac) magnetic susceptibilities reveal slow magnetic relaxation at an applied dc field of 0.1 T in 1, which is characteristic of a field-induced single-ion magnet (SIM), but 2 does not exhibit single-ion magnetic properties at 1.8 K. Detailed analyses of relaxation times show a dominant contribution of a Raman process for spin relaxation in 1.

9.
Anal Biochem ; 557: 104-110, 2018 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-30030995

RESUMO

Indole is a chemical from the decomposition of shrimp and is used extensively to indicate seafood freshness. US Food and Drug Administration (FDA) sets its concentration of <25 µg/100 g shrimp as the threshold for Class I (fresh shrimp). A novel optical probe is reported to quantitatively analyze trace indole in shrimp, including the Class I threshold concentration. Based on an Ehrlich-type reaction, visible spectroscopic analysis of indole in petroleum ether gives a limit of detection (LoD) and quantification (LoQ) of 0.05 and 0.16 µg mL-1, respectively. For 25 µg indole/100 g shrimp extracted into petroleum ether, the probe successfully detects it and the color change is visible to the naked eye. Analysis of the probe response by a visible spectrometer leads to quantification of ≤25 µg indole/100 g shrimp, when recovery is accounted for. When a handheld colorimeter, based on the CIELAB color space, and a smartphone with Bluetooth connectivity are used, the probe demonstrates similar sensitivity for indole in shrimp. The current probe is made of 4-(dimethylamino)benzaldehyde (DMAB) and catalyst p-toluenesulfonic acid (PTSA) in thin films. Indole in shrimp samples after extraction reacts with DMAB to give red ß-bis(indolyl)methane.


Assuntos
Corantes Fluorescentes/química , Contaminação de Alimentos/análise , Indóis/análise , Imagem Óptica , Penaeidae/química , Animais , Estrutura Molecular
10.
Dalton Trans ; 47(32): 11030-11040, 2018 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-30027176

RESUMO

Tri-amidinate chloride complexes M[MeC(NiPr)2]3Cl [M = Zr (1), Hf (2)] have been prepared from MCl4 and lithium amidinate Li[MeC(NiPr)2]. The uncommon hepta-coordinated complexes Zr-Cl (1) and Hf-Cl (2) undergo metathesis reactions with 1 equiv. of MeLi and EtMgCl to give alkyl derivatives M[MeC(NiPr)2]3R [R = Me, M = Zr (3), Hf (4); R = Et, M = Zr (5), Hf (6)]. The dynamic behaviors of Zr-Cl (1) and Hf-Cl (2) in solution have been studied using variable-temperature 1H NMR (VT 1H NMR), giving activation parameters ΔH‡, ΔS‡, and ΔG‡ for several exchange processes in Zr-Cl (1) and Hf-Cl (2). 1H-15N gHMBC NMR spectroscopy gives the chemical shifts of the N atoms in 1-6. The 1H-15N gHMBC NMR spectra of 1-4 at elevated temperatures are needed to obtain signals. Crystal structures of Zr-Cl (1), Hf-Cl (2), Zr-Et (5), and Hf-Et (6) have been determined via X-ray diffraction. DART-MS studies of Zr-Cl (1) and Hf-Cl (2) in air give MS of 1-2, cations M[MeC(NiPr)2]3+ [M = Zr (7), Hf (8)], and hydroxyl complexes M[MeC(NiPr)2]3OH [M = Zr (9), Hf (10)]. In comparison, DART-MS spectra of 3-6 in air show only 7-8 and 9-10, indicating lability of the alkyl ligands and/or their fast hydrolysis by moisture.

11.
Chem Commun (Camb) ; 54(56): 7830-7833, 2018 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-29947374

RESUMO

The reaction of a pentadentate NHC ligand precursor with Ni(OAc)2·4H2O or Pd(OAc)2 in the presence of a base yields four-coordinate square-planar Ni(ii) and Pd(ii) complexes with an unusual ligand generated in situ. A series of experimental studies point to a ring-opening and ring-closing process via novel C-N bond cleavage and formation.

12.
Dalton Trans ; 47(19): 6742-6753, 2018 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-29713716

RESUMO

A series of Ag(i) and Cu(i) complexes [Ag3(L1)2][PF6]3 (8), [Ag3(L2)2][PF6]3 (9), [Cu(L1)][PF6] (10) and [Cu(L2)][PF6] (11) have been synthesized by reactions of the tridentate amine-bis(N-heterocyclic carbene) ligand precursors [H2L1][PF6]2 (6) and [H2L2][PF6]2 (7) with Ag2O and Cu2O, respectively. Complexes 10 and 11 can also be obtained by transmetalation of 8 and 9, respectively, with 3.0 equiv. of CuCl. A heterometallic Cu/Ag-NHC complex [Cu2Ag(L1)2(CH3CN)2][PF6]3 (12) is formed by the reaction of 8 with 2.0 equiv. of CuCl. All complexes have been characterized by NMR, electrospray ionization mass spectrometry (ESI-MS), and single-crystal X-ray diffraction studies. The luminescence properties of 10-12 in solution and the solid state have been studied. At room temperature, 10-12 exhibit evident luminescence in solution and the solid state. The emission wavelengths are found to be identical at 483 nm in CH3CN, but they are 484, 480 and 592 nm in the solid state for 10-12, respectively. These results suggest that 12 dissociates into two molecules of 10 and Ag(i) ions in solution. Complex 12 is the first luminescent heterometallic Cu/Ag-NHC complex.

13.
Dalton Trans ; 47(12): 4282-4292, 2018 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-29487933

RESUMO

A series of Ni(ii), Pd(ii) and Pt(ii) complexes [ML][PF6]2 [L = L1, M = Ni (1), Pd (2), Pt (3); L = L2, M = Ni (4), Pd (5), Pt (6)] and [Pt(L2)(acac)] (7) have been prepared by the reactions of two tetradentate macrocyclic amine-NHC ligand precursors, [H2L1][PF6]2 and [H2L2][PF6]2, with Ni(OAc)2·4H2O, Pd(OAc)2 and Pt(acac)2 in the presence of NaOAc. Complex 7 is isolated along with 6 from the same reaction between [H2L2][PF6]2 and Pt(acac)2. There are two atropisomers in 1-3 and two achiral conformers in 4-6. The crystal structures of 1-3 and one conformer of 4-6 (4a-6a) have been determined by single-crystal X-ray diffraction studies. The metal ion is found to reside in the cavity of the macrocyclic ring and adopts a square-planar configuration. Detailed NMR studies including variable-temperature NMR spectroscopy reveal a dynamic interconverting process between two atropisomers of 1-3 in the solutions via a ring twisting mechanism. Two conformers in the equilibrated solution of 4-6, probably arising from the orientation of two amine N-H bonds with respect to the coordination plane, exchange slowly. Time-dependent 1H NMR spectra show that one conformer (4a-6a) in solution converts into the other (4b-6b) via the inversion of the nitrogen atom.

14.
Ozone Sci Eng ; 39(1): 61-66, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29170573

RESUMO

Whole blood is a complex mixture of biological and chemical species. Its pretreatment, which is often conducted by dry ashing, is needed before the analyses of trace metals in whole blood. Recently photo-Fenton Advanced Oxidation Process (AOP) process has been used in the pretreatment of whole blood. Two new AOP processes using simple heating and microwave irradiation have been developed in the current work to pretreat blood samples. The treatments are based on a Fenton-like AOP with acid deactivation of the enzyme catalase. The first treatment is performed with a lab oven over 5 h, while the second uses microwave irradiation for 6 min. These methods allow for either cost-effective pretreatment through the use of the lab oven, or time savings through the use of the microwave oven. The degradations of blood and pure hemoglobin samples are compared through UV/visible spectroscopy, and the copper concentration in the treated samples were analyzed via anodic stripping voltammetry as a demonstration of analyzing trace metals in the pretreated whole blood.

15.
Inorg Chem ; 56(19): 11917-11928, 2017 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-28933540

RESUMO

A hexadentate macrocyclic N-heterocyclic carbene (NHC) ligand precursor (H4L)(PF6)4 containing four benzimidazolium and two secondary amine groups, has been synthesized and characterized. Coordination chemistry of this new macrocyclic diamine-tetracarbene ligand has been studied by the synthesis of its Ag(I), Au(I), Ni(II), and Pd(II) complexes. Reactions of (H4L)(PF6)4 with different equiv of Ag2O result in Ag(I) complexes [Ag(H2L)](PF6)3 (1) and [Ag2(H2L)](PF6)4 (2). A mononuclear Au(I) complex [Au(H2L)](PF6)3 (3) and a trinuclear Au(I) complex [Au3(H2L)(Cl)2](PF6) (4) are obtained by transmetalation of 1 and 2 with AuCl(SMe2), respectively. Reactions of (H4L)(PF6)4 with Ni(OAc)2 and Pd(OAc)2 in the presence of NaOAc yield [Ni(L)](PF6)2 (5) and [Pd(L)](PF6)2 (6), respectively, containing one Ni(II) and Pd(II) ion with distorted square-planar geometry. Using more NaOAc results in the formation of unusual dinuclear complexes [Ni2(L-2H)](PF6)2 (7) and [Pd2(L-2H)](PF6)2 (8) (L-2H = deprotonated ligand after removing two H+ ions from two secondary amine groups in L), respectively, featuring a rare M2N2 core formed by two bridging amides. 7 is also formed by the reaction of 5 with 1.0 equiv of Ni(OAc)2·4H2O in the presence of NaOAc. Transmetalation of 2 with 2.0 equiv of Ni(PPh3)2Cl2 gives [Ni2(L)(µ-O)](PF6)2 (9), the first example of a dinuclear Ni(II) complex with a singly bridging oxo group. 9 is converted to 7 in good yield through the treatment with NaOAc.

16.
Chem Commun (Camb) ; 53(67): 9304-9307, 2017 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-28737799

RESUMO

We present the first examples of the coexistence of field induced slow magnetic relaxation and spin-crossover observed in five-coordinate cobalt(ii) complexes [Co(12-TMC)(CH3CN)](X)2 (12-TMC = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane, X = BF4-, 1; PF6-, 2). The direct-current (dc) magnetic data show a gradual and incomplete spin-crossover at high temperature. 1 and 2 display frequency- and temperature-dependent alternating-current (ac) magnetic susceptibility under an applied dc field of 2500 Oe, which originates from the S = 1/2 spin state of Co(ii) ions.

17.
Inorg Chem ; 56(12): 7111-7119, 2017 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-28581727

RESUMO

The reactions of early-transition-metal complexes with H2O have been investigated. An understanding of these elementary steps promotes the design of precursors for the preparation of metal oxide materials or supported heterogeneous catalysts. Density functional theory (DFT) calculations have been conducted to investigate two elementary steps of the reactions between tungsten alkylidyne complexes and H2O, i.e., the addition of H2O to the W≡C bond and ligand hydrolysis. Four tungsten alkylidyne complexes, W(≡CSiMe3)(CH2SiMe3)3 (A-1), W(≡CSiMe3)(CH2tBu)3 (B-1), W(≡CtBu)(CH2tBu)3 (C-1), and W(≡CtBu)(OtBu)3 (D-1), have been compared. The DFT studies provide an energy profile of the two competing pathways. An additional H2O molecule can serve as a proton shuttle, accelerating the H2O addition reaction. The effect of atoms at the α and ß positions has also been examined. Because the lone-pair electrons of an O atom at the α position can interact with the orbital of the proton, the barrier of the ligand-hydrolysis reaction for D-1 is dramatically reduced. Both the electronic and steric effects of the silyl group at the ß position lower the barriers of both the H2O addition and ligand-hydrolysis reactions. These new mechanistic findings may lead to the further development of metal complex precursors.

18.
Inorg Chem ; 55(24): 12603-12617, 2016 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-27989182

RESUMO

Three mononuclear cobalt(II) tetranitrate complexes (A)2[Co(NO3)4] with different countercations, Ph4P+ (1), MePh3P+ (2), and Ph4As+ (3), have been synthesized and studied by X-ray single-crystal diffraction, magnetic measurements, inelastic neutron scattering (INS), high-frequency and high-field EPR (HF-EPR) spectroscopy, and theoretical calculations. The X-ray diffraction studies reveal that the structure of the tetranitrate cobalt anion varies with the countercation. 1 and 2 exhibit highly irregular seven-coordinate geometries, while the central Co(II) ion of 3 is in a distorted-dodecahedral configuration. The sole magnetic transition observed in the INS spectroscopy of 1-3 corresponds to the zero-field splitting (2(D2 + 3E2)1/2) from 22.5(2) cm-1 in 1 to 26.6(3) cm-1 in 2 and 11.1(5) cm-1 in 3. The positive sign of the D value, and hence the easy-plane magnetic anisotropy, was demonstrated for 1 by INS studies under magnetic fields and HF-EPR spectroscopy. The combined analyses of INS and HF-EPR data yield the D values as +10.90(3), +12.74(3), and +4.50(3) cm-1 for 1-3, respectively. Frequency- and temperature-dependent alternating-current magnetic susceptibility measurements reveal the slow magnetization relaxation in 1 and 2 at an applied dc field of 600 Oe, which is a characteristic of field-induced single-molecule magnets (SMMs). The electronic structures and the origin of magnetic anisotropy of 1-3 were revealed by calculations at the CASPT2/NEVPT2 level.

19.
Anal Chim Acta ; 914: 47-52, 2016 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-26965326

RESUMO

Anodic stripping voltammetry, a classical electroanalytical method has been optimized to analyze trace Pd(II) in active pharmaceutical ingredient matrices. The electroanalytical approach with an unmodified glassy carbon electrode was performed in both aqueous and 95% DMSO/5% water (95/5 DMSO/H2O) solutions, without pretreatment such as acid digestion or dry ashing to remove the organics. Limits of detection (LODs) in the presence of caffeine and ketoprofen were determined to be 11 and 9.6 µg g(-1), with a relative standard deviation (RSD) of 5.7% and 2.3%, respectively. This method is simple, highly reproducible, sensitive, and robust. The instrumentation has the potential to be portable and the obviation of sample pretreatment makes it an ideal approach for determining lost catalytic metals in pharmaceutical-related industries. Furthermore, the simultaneous detection of Pd(II) with Cd(II) and Pb(II) in the low µg L(-1) range indicates that this system is capable of simultaneous multi-analyte analysis in a variety of matrices.


Assuntos
Técnicas Eletroquímicas/métodos , Eletrodos , Paládio/análise , Preparações Farmacêuticas/química
20.
Anal Chem ; 88(3): 1553-8, 2016 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-26742539

RESUMO

A new sensor for the detection of hydrogen sulfide (H2S) gas has been developed to replace commercial lead(II) acetate-based test papers. The new sensor is a wet, porous, paper-like substrate coated with Bi(OH)3 or its alkaline derivatives at pH 11. In contrast to the neurotoxic lead(II) acetate, bismuth is used due to its nontoxic properties, as Bi(III) has been a reagent in medications such as Pepto-Bismol. The reaction between H2S gas and the current sensor produces a visible color change from white to yellow/brown, and the sensor responds to ≥ 30 ppb H2S in a total volume of 1.35 L of gas, a typical volume of human breath. The alkaline, wet coating helps the trapping of acidic H2S gas and its reaction with Bi(III) species, forming colored Bi2S3. The sensor is suitable for testing human bad breath and is at least 2 orders of magnitude more sensitive than a commercial H2S test paper based on Pb(II)(acetate)2. The small volume of 1.35-L H2S is important, as the commercial Pb(II)(acetate)2-based paper requires large volumes of 5 ppm H2S gas. The new sensor reported here is inexpensive, disposable, safe, and user-friendly. A simple, laboratory setup for generating small volumes of ppb-ppm of H2S gas is also reported.


Assuntos
Bismuto/química , Gases/análise , Sulfeto de Hidrogênio/análise , Papel , Monitoramento Ambiental , Humanos , Concentração de Íons de Hidrogênio , Tamanho da Partícula , Porosidade , Propriedades de Superfície
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