Optical Sensor Based on Nanomaterial for the Selective Detection of Toxic Metal Ions

A heterogeneous “naked‐eye” colorimetric and spectrophotometric cation sensor, SNT‐ 1 , was prepared by immobilization of the azo‐coupled macrocyclic receptor 1 on a silica nanotube (SNT) via sol–gel reaction. The optical sensing ability of SNT‐ 1 was studied by addition of metal ions such as Ag⁺, Co²⁺, Cd²⁺, Pb²⁺, Zn²⁺, Fe³⁺, Cu²⁺, and Hg²⁺ (all as nitrates) in water. Upon the addition of Hg²⁺ in suspension SNT‐ 1 resulted in a color change from yellow to violet. This is novel rare example for chromogenic sensing of a specific metal ion by inorganic nanotubes. On the other hand, no significant changes in color were observed in the parallel experiments with Co²⁺, Cd²⁺, Pb²⁺, Zn²⁺, Fe³⁺, Cu²⁺, and Ag⁺. These findings confirm that SNT‐ 1 can be useful as chemosensors for selective detection of Hg²⁺ over a range of metal ions. More interestingly, after addition of NO₃^– and ClO₄^– SNT‐ 1 was observed to change color from yellow to violet and pink, respectively. However, no color changes were observed upon addition of Cl^–, Br^–, I^–, SCN^–, or SO₄^2–. Furthermore, the extraction ability of SNT‐ 1 was also estimated by measuring the amount of Hg²⁺ adsorbed by ion chromatography, showing that 95 % of the Hg²⁺ ion is extracted by SNT‐ 1 . This suggests that SNT‐ 1 is potentially useful as a stationary phase for the separation of Hg²⁺ in liquid chromatography. In order to extend the above performance to a portable chemosensor kit, SNT‐ 1 was coated as a thin film of 50 μm thickness onto a glass substrate. The supported SNT‐ 1 also changed from yellow to violet when dipped into Hg²⁺ solution. On the other hand, no significant change in color was observed in other metal‐ion solutions. The results imply that the supported SNT‐ 1 is applicable as a portable colorimetric sensor for detection of Hg²⁺ in the field.     

Remarkable Acid Stability of Polypyrrole‐MoS4: A Highly Selective and Efficient Scavenger of Heavy Metals Over a Wide pH Range

The new material polypyrrole/MoS₄^2?(MoS₄‐Ppy), prepared by ion‐exchange of NO₃‐ of NO₃‐Ppy with MoS₄^2?, displays high acid stability and excellent uptake for heavy metal ions such as Hg²⁺, Ag⁺, Cu²⁺, and Pb²⁺. The different maximum adsorption capacities (q_m) for Cu²⁺, Pb²⁺, Hg²⁺, and Ag⁺ depend on the various binding modes arising from the different thiophilicity of these metal ions. The removals of Ag⁺ and Pb²⁺ reach >99.6% within 5 min, and for highly toxic Hg²⁺, >98% removal achieves at 1 min. At strong acid limit, the exceptional q_m(Ag⁺) of 725 mg g^?1 places the MoS₄‐Ppy at the top of materials for such removal. Uptake kinetics of Ag⁺, Hg²⁺, and Pb²⁺ is extremely fast: >99.9% removal rates at wide pH range (0.5–6) within 1–5 min. Also, at strongly acidic conditions (pH ≈ 1), for highly toxic Hg²⁺, <2 ppb concentration can be achieved, accepted as safe limit. The MoS₄‐Ppy demonstrates an outstanding ability to separate low‐concentrated Ag⁺ from high concentrated Cu²⁺ especially under strong acidic conditions (pH ≈ 1), showing a large separation factor SF_Ag/Cu (K_d^Ag/K_d^Cu) of 10⁵ (>100). MoS₄‐Ppy is a superior and novel sorbent material for water remediation applications as well as precious metals recovery.     

Tailoring Amino‐Functionalized Graphitic Carbon‐Encapsulated Gold Core/Shell Nanostructures for the Sensitive and Selective Detection of Copper Ions

The effective transfer of strong electromagnetic field from the gold core through the coating shell represents the most significant challenge for the applications of plasmonic nanoparticles. This study applies a one‐step arc discharge method to synthesize graphitic carbon‐encapsulated gold nanoparticles (Au@G NPs) functionalized with amino groups uniformly via adding NH₃ into He background gas. By tailoring the coating shell into few‐layered graphene, a strong localized surface plasmon resonance (LSPR) absorption band is achieved. The NH₃ introduces H radicals to strengthen the LSPR characteristic by etching the coating graphitic shell, as well as provides dissociated NH or NH₂ species to functionalize the surfaces with amino groups. With an LSPR‐based colorimetric method, it is demonstrated that trace Cu²⁺ ions can be detected rapidly with excellent sensitivity (as low as 10 × 10^‐9m linearly) and selectivity against other metal ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Co²⁺, Fe²⁺, Cd²⁺, Pb²⁺, and Hg²⁺ ions) by amino‐functionalized Au@G NPs in water samples.     

An Alternative Copolymer of Carbazole and Thieno[3,4b]‐Pyrazine: Synthesis and Mercury Detection

A donor‐π‐acceptor (D‐π‐A) alternative copolymer of carbazole and thieno[3,4b]‐pyrazine [P(CZ‐TPZ)] is synthesized through a Wittig–Horner reaction. In dilute THF solution, the absorption spectrum of P(CZ‐TPZ) shows two absorption peaks at 306 and 452 nm, respectively, and the PL spectrum of the polymer solution displays a PL peak maximum at 543 nm. The polymer possesses relatively high sensitivity and selectivity for Hg²⁺ detection. Upon addition of Hg²⁺ into its THF solution (containing 0.3% CH₃CN), P(CZ‐TPZ) exhibits a new absorption peak at 560～600 nm and its emission was quenched dramatically. The Hg²⁺ detection shows high selectivity in comparison with the other cations of Na⁺, K⁺, Mg²⁺, Ba²⁺, Al³⁺, Cu²⁺, Cd²⁺, Pb²⁺, Ni²⁺, Mn²⁺, and Co²⁺. The Hg²⁺ detection limit of the polymer solution by emission quenching is found to be 1 × 10^?7 mol L^?1. P(CZ‐TPZ) also shows a selective chromogenic behavior toward Hg²⁺ with color change of the solution from yellow to blue dark which can be detected with the naked eye, the detection limit reaches 1 × 10^?6 mol L^?1 with a 1 × 10^?4 mol L^?1 polymer solution. The absorption and PL spectral change can be resumed after adding thiourea, therefore the sensing ability of the polymer is re‐usable with the treatment of thiourea. The results indicate that P(CZ‐TPZ) is a promising chemosensor for the Hg²⁺ detection.     

Thermo‐Switchable Charge Transport and Electrocatalysis Using Metal‐Ion‐Modified pNIPAM‐Functionalized Electrodes

Metal ions (Ag⁺, Cu²⁺, Hg²⁺) are incorporated into an electropolymerized, poly(N‐isopropyl acrylamide), pNIPAM, thermosensitive polymer associated with an electrode using the “breathing‐in” method. The ion‐functionalized pNIPAM matrices reveal ion‐dependent gel‐to‐solid phase‐transition temperatures (28 ± 1 °C, 25 ± 1 °C, 40 ± 1 °C for the Ag⁺, Cu²⁺, and Hg²⁺‐modified pNIPAM, respectively). Furthermore, the ion‐functionalized polymers exhibit quasi‐reversible redox properties, and the ions are reduced to the respective Ag⁰, Cu⁰, and Hg⁰ nanocluster‐modified polymers. The metal‐nanocluster‐functionalized pNIPAM matrices enhance the electron transfer (they exhibit lower electron‐transfer resistances) in the compacted states. The electron‐transfer resistances of the metal‐nanocluster‐modified pNIPAM can be cycled between low and high values by temperature‐induced switching of the polymer between its contracted solid and expanded gel states, respectively. The enhanced electron‐transfer properties of the metal nanocluster‐functionalized polymer are attributed to the contacting of the metal nanoclusters in the contracted state of the polymers. This temperature‐switchable electron transfer across a Ag⁰‐modified pNIPAM was implemented to design a thermo‐switchable electrocatalytic process (the temperature‐switchable electrocatalyzed reduction of H₂O₂ by Ag⁰‐pNIPAM).     

Functionalized Cubic Mesoporous Silica as a Non‐Chemodosimetric Fluorescence Probe and Adsorbent for Selective Detection and Removal of Bisulfite Anions along with Toxic Metal Ions

Dual signaling and remediation systems for detection and adsorption of toxic analytes have gained more attention over sensory probes only. However, most of the sensors for bisulfites are chemodosimetric probes, which are irreversible and having drawbacks of absolute selectivity, recyclability, and solubility in a pure aqueous system. To address above drawbacks a new non‐chemodosimetric probe material with a strong hydrogen bonding pocket for bisulfites is developed. Synthesis of cubic mesoporous silica by a modified Stober process followed by functionalization with 2,2′‐(((((3‐(triethoxysilyl)propyl)azanediyl)bis(methylene))bis(2,1‐phenylene))bis(oxy))bis(N‐(4‐((E)‐phenyldiazenyl)phenyl)acetamide) (AZOL) has given a fluorogenic silica probe material SiO₂@AZOL. This material shows selectivity toward bisulfite anion (limit of detection (LOD): 64 ppb) and Hg²⁺, Cd²⁺, Cu²⁺, and Zn²⁺ cations (LOD: 126, 95, 14, and 27 ppb, respectively) among various analytes. The adsorption studies for these toxic analytes (HSO₃ ^?, Hg²⁺, Cd²⁺, Cu²⁺, and Zn²⁺) show an extraction efficiency of around 99% and adsorption capacities of 873, 630, 633, 260, and 412 mg g^?1, respectively. Spectroscopic studies along with adsorption, striping, and regeneration studies reveal that this material is a recyclable sensory cum adsorbent material for these toxic analytes. Moreover, this material can be used as a sensitive probe material for determination of HSO₃ ^? levels in various sugar samples.     

H2xMnxSn3‐xS6 (x = 0.11–0.25): A Novel Reusable Sorbent for Highly Specific Mercury Capture Under Extreme pH Conditions

The H_2xMn_xSn_3‐xS₆ (x = 0.11–0.25) is a new solid acid with a layered hydrogen metal sulfide (LHMS). It derives from K_2xMn_xSn_3–xS₆ (x = 0.5–0.95) (KMS‐1) upon treating it with highly acidic solutions. We demonstrate that LHMS‐1 has enormous affinity for the very soft metal ions such as Hg²⁺ and Ag⁺ which occurs via a rapid ion exchange process. The tremendous affinity of LHMS‐1 for Hg²⁺ is reflected in very high distribution coefficient K_d^Hg values (>10⁶ mL g^?1). The large affinity and selectivity of LHMS‐1 for Hg²⁺ persists in a very wide pH range (from less than zero to nine) and even in the presence of highly concentrated HCl and HNO₃ acids. LHMS‐1 is significantly more selective for Hg²⁺ and Ag⁺ than for the less soft cations Pb²⁺ and Cd²⁺. The Hg²⁺ ions are immobilized in octahedral sites between the sulfide layers of the materials via Hg–S bonds as suggested by pair distribution function (PDF) analysis. LHMS‐1 could decrease trace concentrations of Hg²⁺ (e.g. <100 ppb) to well below the acceptable limits for the drinking water in less than two min. Hg‐laden LHMS‐1 shows a remarkable hydrothermal stability and resistance in 6 M HCl solutions. LHMS‐1 could be regenerated by treating Hg‐loaded samples with 12 M HCl and re‐used without loss of its initial exchange capacity.     

Electrochemical investigations for copper electrodeposition of through-silicon via

This study uses electrochemical techniques with a rotating disk electrode (RDE) to investigate the effects of Cu²⁺ concentration and additives on electrodeposition of through-silicon vias (TSV). The plating bath with both PEG and SPS has an obvious suppression effect on Cu-RDE with a thin boundary layer from −350 to −634 mV (vs. Hg/Hg₂SO₄) and a wide potential range for the via-filling operation. The impedance and potentiodynamic scans show the adsorption of small molecule SPS is more stable than PEG, and the effect of PEG or SPS depends on the thickness of boundary layer obviously only in Tafel region. This study obtained high filling powers in both deep and shallow vias using the plating bath of 50 g/L Cu²⁺, and TSV filling in wafer-segment scale, with 20 μm via diameter and 100 μm via depth, verifies the performance predicted by the electrochemical techniques.     

Nanostructured TiO2 modified with acetohydrazide zinc porphyrin well-arrays for supramolecular solar cells

In this work, employing the metal-mediated assembling strategy for organizing acetohydrazide zinc porphyrin (ZnP) and different organic acid (Ai) ligands on the nanostructured TiO₂ electrode surfaces have been prepared, wherein the ZnP and Ai units are bound by a series of differently bivalent metal ions (M, M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Hg²⁺), resulting in a ZnP–M–Ai assembled approach. The photovoltaic performances of these assemblies-sensitized solar cells were performed under irradiance of 100 mW cm⁻² AM 1.5G sunlight. A significantly improved conversion efficiency of ZnP–Mn–A5 and ZnP–Cd–A5 devices occurs, indicating well-ordered arrangements of ZnP molecules on the TiO₂ electrode surfaces for ZnP–Mn–A5 and ZnP–Cd–A5, where A5 is a pyridine–monocarboxylic acid ligand bearing longer arm. The results were also verified by the HOMO–LUMO gaps, UV–vis and fluorescence spectra.     

Highly Fluorescent Conjugated Polyelectrolyte Nanostructures: Synthesis,Self‐Assembly,and Al3+ Ion Sensing

A highly fluorescent triazine‐bridged polymer, poly[(diphenylamino‐s‐triazine)‐co‐(2‐methoxy‐5‐propyloxysulfonate‐1,4‐phenylene vinylene)] (DTMSPV), is synthesized from Wittig polycondensation of a triazine monomer with a water‐soluble p‐phenylene vinylene monomer. The fluorescent amphiphilic polymer in aqueous solution self‐assembled into nanoassemblies of micelle‐like nanostructure (MS) and π stacking nanostructure (πS), which have average sizes of 93 to 270 nm, depending on the concentration of DTMSPV. The micelle‐like nanostructure of DTMSPV (MS) shows blue emission at 457 and 488 nm with a high emission quantum yield (Φ_E) of 31% in aqueous solution. On the other hand, the Φ_E of π stacking structures (πS), formed in a highly concentrated solution, is lower than the MS. The MS exhibits fluorescence quenching as well as color change from blue to green/yellow, depending on the kinds of metal ions. The metal ion sensitivity is larger in the order of the main group ions (Na⁺, K⁺) < dicationic transition metal ions (Zn²⁺, Cd²⁺, Pb²⁺, Cu²⁺, Pd²⁺) < trivalent transition metal ions (Fe³⁺, Ru³⁺), with an exception of Al³⁺. In particular, the fluorescence of MS is dramatically quenched with color change to yellow in response to Al³⁺ concentrations. The selectivity and sensitivity of MS to Al³⁺ are unusually high even in the presence of competitive metal ions, which can be attributed to the specific interaction of triazine units with Al³⁺.     

Intelligent Molecular Searcher from Logic Computing Network Based on Eu(III) Functionalized UMOFs for Environmental Monitoring

By taking advantage of facile preparation and sensitive recognition capacity, the first example of a fluorescence system based on Eu(III) functionalized UiO(bpdc) (UMOFs) has been constructed for effective combination of ions recognition and logic computing. All the ions, including Hg²⁺, Ag⁺, and S^2? in the system are water harmful, which can be recognized through affecting energy transfer or framework structure. By the self‐assembling, competing and connecting with each other, Eu(III)@UMOFs and the ions have achieved the implementation of Boolean logic network system connecting the elementary logic operations (NOR, INH, and IMP) and integrative logic operation (OR + INH), also obtaining computing keypad‐lock security system by sequential logic operation. To deal with uncertain information in the analog region of nonlinear response (fluorescence and concentration), soft computation through the formulation of fuzzy logic operation has been constructed. On the basis of Boolean logic and fuzzy logic, one intelligent molecular searcher can be realized by taking chemical events (Hg²⁺, Ag⁺, and S^2?) as programmable words and chemical interactions as syntax. Considering the particularity of all the input ions, the approach is helpful in developing the advanced logic program based on Eu(III)@UMOFs for application in environmental monitoring.     

Ion-selective langmuir blodgett films of a chromoionophore

Langmuir–Blodgett films built up from an amphiphilic derivative of benzothiazolium styryl dye containing a 1,10-dithia-18-crown-6 ether group have been found to complex with ‘soft’ polarisable ions such as Ag⁺ and Hg²⁺ in water. The films exhibited high sensitivity (stability constant of complex formation K ≈ 10⁵ M^?1) and high selectivity (e.g. K(Ag⁺)/K(Pb²⁺)> 10⁵) compared with aqueous solutions of similar ionophores. This was attributed to the predominant formation of complexes with ligand–cation stoichiometries of 2:1 in the films.     

Effect of successive implantation of Ag+(Cu+) and Xe+ ions on the recombination properties of CdxHg1−x Te crystals

The effect of successive double implantation of Ag⁺(Cu⁺) and Xe⁺ ions on the recombination properties of Cd_xHg_1−x Te (0.2<x<0.3) crystals has been investigated. It is shown that after implantation of ions of one chemical element, followed by diffusion thermal annealing at temperatures below 150–200 K, recombination through local levels lying 30±5 meV below the conduction band bottom dominates. Successive double implantation of Ag⁺(Cu⁺) and Xe⁺ ions followed by diffusion thermal annealing changes the course of the temperature dependence of the lifetime of the nonequilibrium charge carriers. It was determined that for Cd_xHg_1−x Te crystals with x⋍0.20–0.25 in the temperature interval 700–200 K the lifetime of the nonequilibrium charge carriers is low (τ<0.15 μs) and does not depend on the temperature. For Cd_xHg_1−x Te crystals with x⋍0.3 recombination of nonequilibrium charge carriers occurs through two types of levels: in the temperature range 140–200 K — deep levels E _t1⋍E _c −51 meV and at lower temperatures (77–140 K) — through shallower levels E _t2⋍E _c −(16±2) meV. Fiz. Tekh. Poluprovodn. 31, 786–789 (July 1997)     

Functionalized Mesoporous Photonic Crystal Film for Ultrasensitive Visual Detection and Effective Removal of Mercury (II) Ions in Water

Mercury ion (Hg²⁺) contamination is a worldwide serious environment problem; exploring smart sensing and adsorption materials are urgently demanded for Hg²⁺ monitoring and removal. Herein, a simple 1D photonic crystal to first ever feature capabilities of visually quantitative determination and effective adsorption toward Hg²⁺ is facilely constructed by integrating a specifically designed thiourea-functionalized nanocopolymer layer with a mesoporous TiO₂ layer. Based on strong chelation and porous structure, Hg²⁺ is easily adsorbed on the copolymer and triggers vertically volumetric shrinkage, resulting in highlighted wavelength blue-shifts and color changes in a broad Hg²⁺ level scope. Utilizing the adsorption characteristic, Hg²⁺ existing in aqueous media can be effectively removed by the photonic film with a remarkable uptake capacity of 739.6 mg g⁻¹. This portable nanolayered film exhibits full regeneration, facile recovery, desirable selectivity toward Hg²⁺, and shields interference from other metal ions, which enables future application for environmental determination and remediation. Furthermore, a novel nanopolymer-based two-regime Hg²⁺-capturing mechanism is first revealed by quartz crystal microbalance with dissipation monitoring, providing valuable references for future relevant adsorption researches.     

Nanoconfinement-Controlled Synthesis of Highly Active,Multinary Nanoplatelet Catalysts from Lamellar Magic-Sized Nanocluster Templates

Magic-sized semiconductor nanoclusters (MSCs) possessing intermediate stability are promising precursors for synthesizing low-dimensional nanostructures that cannot be achieved by direct methods. However, uncontrolled diffusion of MSCs in their colloidal-state poses challenges in utilizing them as precursors and/or templates for the controlled synthesis of nanomaterials. Herein, a nanoconfined diffusion-limited strategy to synthesize large CdSe nanoplatelets through the solid-state transformation of (CdSe)₁₃ MSCs is designed, wherein MSCs serve as both precursors and lamellar bilayer templates. In sharp contrast, in the colloidal-state, these MSCs are grown to CdSe nanoribbons or nanorods. Furthermore, the nanoconfined route is used not only to transform (CdSe)₁₃, Mn²⁺:(CdSe)₁₃, and Mn²⁺:(Cd_1−xZn_xSe)₁₃ MSCs but also to dope Cu⁺, producing Cu⁺:CdSe, Mn²⁺/Cu⁺:CdSe, Mn²⁺/Cu⁺:Cd_1−xZn_xSe nanoplatelets, respectively. The resulting multinary nanoplatelets with controlled compositions exhibit unique optical and magneto-optical properties through characteristic exciton transfer mechanisms. Furthermore, synergistic effects have made quinary Mn²⁺/Cu⁺:Cd_0.5Zn_0.5Se nanoplatelets efficient and reusable catalysts for chemical fixation of CO₂ with epoxide (turnover frequency: ≈200/h) under mild conditions. This nanoconfined synthetic strategy paves the way to synthesize diverse shape-controlled multi-component nanostructures for optoelectronic and other catalytic applications.     

Monovalent Charge Compensation Enables Efficient Lanthanide-Based Near-Infrared Perovskite LEDs

Lanthanide ions (Yb³⁺ or Er³⁺) alloying of CsPb(Cl_1-xBr_x)₃ quantum dots (QDs) to emit approaching 1000 nm show promise in near-infrared light-emitting diodes (NIR-LEDs). High Yb³⁺ alloying ratio increases the electroluminance efficiency of emission at 990 nm and enables high external quantum efficiency (EQE) of NIR-LEDs, however, the high alloying ratio also results in inferior material stability and PLQY drop because of Yb³⁺-induced nanocrystal precipitation. This study finds that the heavy alloying of Yb³⁺ ions causes lattice distortion and coherent energy reduction of Yb³⁺: CsPb(Cl_1-xBr_x)₃ QDs, induced by two Yb³⁺ ions replacing three Pb²⁺, which leads to the collapse of the octahedral structure in ambient conditions. It posits that spontaneous monovalent ion (Na⁺) alloying can address the trade-off between material stability and emission intensity. The Na⁺ occupies the vacancy of Pb²⁺ ions, relaxing the distortion in the lattice and improving the phase stability of octahedral structure, and this optimized structure in turn allows a higher Yb³⁺ alloying ratio. Stability measurements show that the Na⁺/Yb³⁺ co-alloyed films show ten-fold higher material stability and 2.0-fold emission efficiency related to controls. It reports that as a result Na⁺/Yb³⁺ co-alloyed NIR-LEDs have an EQE of 6.4% at 990 nm, which is among the highest perovskite NIR-LEDs beyond 950 nm.     

Status of MBE technology for the flexible manufacturing of HgCdTe focal plane arrays

A robust process has been developed for the reproducible growth of in-situ doped Hg_1−xCd_xTe:As alloys by molecular beam epitaxy. Net hole concentrations in excess of 5 x 10¹⁷ cm⁻³, with peak mobilities >200 cm2/Vs were measured in Hg_0.74Cd_0.26Te:As films. The p-type layers were twin-free and consistently exhibit narrow x-ray rocking curves (<40 arc sec). The reproducible growth of small lots of p-on-n LWIR detector structures has been established. For a typical lot consisting of 13 layers, the average x-value of the n-type base layer was 0.226 with a standard deviation of 0.003. The lateral compositional uniformity across a 2.5 cm × 2.5 cm wafer was × = +- 0.0006. High performance p-on-n LWIR diodes were fabricated that exhibited R_oA_o values (0-fov at 78K) as large as 350 Q cm2 at 10.4 μm.     

Molecular beam epitaxy of CdTe and Hg1-xCdxTe ON GaAs (100)

Using the molecular beam epitaxial (MBE) technique, CdTe and Hg_1-xCd_xTe have been grown on Cr-doped GaAs (100) sub-strates. A single effusion cell charged with polycrystal-line CdTe is used for the growth of CdTe films. The CdTe films grown at 200 °C with a growth rate of ~ 2 μm/hr show both streaked and “Kikuchi” patterns, indicating single crystalline CdTe films are smoothly grown on the GaAs sub-strates. A sharp emission peak is observed at near band-edge (7865 Å, 1.577 eV) in the photoluminescence spectrum at 77 K. For the growth of Hg_1-xCd_xTe films, separate sources of HgTe, Cd and Te are used. Hg_0.6Cd_0.4Te films are grown at 50 °C with a growth rate of 1.7 μm/hr. The surfaces are mirror-smooth and the interfaces between the films and the substrates are very flat and smooth. As-grown Hg_0.6Cd_0.4Te films are p-type and converted into n-type by annealing in Hg pressure. Carrier concentration and Hall mobility of an annealed Hg_0.6Cd_0.4Te film are 1 × 10¹⁷ cm^?3 and 1000 cm²/V-sec at 77 K, respectively.     

Preparation,Characterization, and Application of L‐Cysteine Functionalized Multiwalled Carbon Nanotubes as a Selective Sorbent for Separation and Preconcentration of Heavy Metals

L ‐cysteine functionalized multi‐walled carbon nanotubes (MWCNTs‐cysteine) are synthesized and characterized by XPS, FT‐IR, XRD, and TEM. The capability of MWCNTs‐cysteine for selective separation and preconcentration of heavy metal ions are statically and dynamically evaluated with Cd²⁺ as a model heavy metal ion. Unlike MWCNTs, the sorption of Cd²⁺ onto MWCNTs‐cysteine is not influenced by ionic strength in a wide range. The MWCNTs‐cysteine is demonstrated to be good column packings for on‐line microcolumn separation and preconcentration of Cd²⁺. Effective preconcentration of Cd²⁺ on the MWCNTs‐cysteine packed microcolumn is achieved in a pH range of 5.5 to 8.0. The retained Cd²⁺ is efficiently eluted with 0.5 mol L^?1 HCl for on‐line flame atomic absorption spectrometric determination. The MWCNTs‐cysteine exhibit fairly fast kinetics for the adsorption of Cd²⁺, and offer up to 1600‐fold improvement of the tolerable concentrations of co‐existing metal ions over the MWCNTs for on‐line solid‐phase extraction of Cd²⁺. With a preconcentration time of 60 s at a sample loading flow rate of 5.0 mL min^?1, an enhancement factor of 33 and a sample throughput of 36 h^?1 along with a detection limit (3s) of 0.28 µg L^?1 are obtained. The precision (RSD) for 11 replicate measurements is 1.6% at the 10 µg L^?1 level. The developed method using the MWCNTs‐cysteine as sorbent is successfully applied to determination of trace cadmium in a variety of biological and environmental materials.     

The structure and room temperature ferromagnetism property of the ZnS:Cu2+ nanoparticles

ZnS:Cu²⁺ nanoparticles were synthesized by the solvothermal method. The results showed that the nanoparticles with the diameters of 10–20 nm were of cubic zinc blende structure. The Cu²⁺ ions were substitutionally incorporated into the ZnS lattice and the maximum concentration of the Cu²⁺ ions in the ZnS nanoparticles can reach to 2.84%. The ferromagnetism property of the ZnS:Cu²⁺ nanoparticles was observed around room temperature, which was explained by the super-exchange mechanism.