•Develop an in situ modification assisted electrochemical method to synthesize SeNPs.•The synthetic mechanism is an electrode reaction with a following chemical reaction.•The SeNPs modified by sucrose, PVP and SDS are highly dispersed and stable in water.•The sea urchin-like SeNPs-SDS/CTAB are prepared by electrostatic assembly.Electrochemical synthesis has been proved to be a versatile and simple approach for the preparation of nanoparticles. In this work, an electrochemical method was successfully applied to synthesize selenium nanoparticles (SeNPs) via using selenium powder doped carbon paste electrode. SeNPs were spherical with diameters of about 85, 43 and 60 nm and well dispersed in the presence of sucrose, polyvinylpyrrolidone and sodium dodecyl sulfonate (SDS), respectively. Surprisingly, when adding cetane trimethyl ammonium bromide (CTAB) into the spherical SeNPs modified with SDS, spherical SeNPs changed to sea urchin-like SeNPs by electrostatic assembly. The effects of SDS and CTAB on the morphology of SeNPs were investigated.Download high-res image (120KB)Download full-size image

•Developed a green and facile method for synthesizing NCDs from amino acids.•NCDs had good dispersibility and stability and the highest quantum yield reached 41.3%.•The emission of NCDs was highly dependent on excitation energy.•The relationship between luminescent properties and energy band was explained.A green and facile method was developed to synthesize nitrogen doped carbon dots (NCDs) with blue-luminescence by hydrothermal treatment of different amino acids (aspartic acid, glutamic, proline, threonine, valine, phenylalanine, arginine and serine). The NCDs were characterized by various methods and the highest quantum yield reached 41.3%. The formation and surface passivation of NCDs were accomplished simultaneously via dehydration, polymerization, carbonization, and passivation process. The passivation degree of NCDs was controlled by the hydrothermal time. NCDs had good aqueous dispersibility, high stability, and preeminent photoluminescent properties. The emission of NCDs was highly dependent on excitation energy, as the excitation wavelength increased from 300 to 470 nm, the emission peak position shifted from blue to green region with the intensity decreased. These features resulted from the fact that the surface passivation could form the additional interband and we explained the relationship between luminescent properties and energy band in detail.The PL of NCDs was contributed by two transition processes. Process 1 was band to band transition under higher excitation energy. Process 2 was interstate emission and excitation-dependent under the lower excitation energy.Download high-res image (121KB)Download full-size image

•Develop a AuNPs-based colorimetry for selective sensing of SeCys coexisting with Cys.•Cys is oxidized to cystine under Cu2+ catalysis and its interference is eliminated.•The aggregation of AuNPs is induced by Cu2+-SeCys complex via Au-Se bond.•The sensitivity and selectivity are improved by a second-derivative SPR spectrum.We present a highly selective and sensitive colorimetric method for the detection of selenocystine (SeCys) coexisting with other amino acids, especially cysteine (Cys) using the gold nanoparticles (AuNPs). Firstly, Cys was oxidized to cystine (Cys-Cys) by dissolved oxygen under Cu2+ catalysis in the pre-reaction, which eliminated the interference of Cys in the SeCys sensing process. Then SeCys induced the rapid aggregation of AuNPs through Au-Se bond and complex formation of Cu2+-SeCys in the colorimetric reaction, in which the color change of AuNPs from red to blue or purple with the naked eye detection or with a UV-vis spectrophotometric determination. The concentration of SeCys was quantified by the value at 670 nm from the second-derivative SPR absorbance spectrum. The linear range was from 2 μM to 14 μM with correlation coefficient of 0.999 and a detection limit (LOD) was 0.14 μM. Moreover, the colorimetric response of AuNPs exhibited remarkable specificity to SeCys coexisting with 18 amino acids in a simulation sample, in which the total concentration of Cys and Cys-Cys was less than 15 μM and the each concentration of other 16 common amino acids was 10 μM.Download high-res image (211KB)Download full-size image

The nanoSe0-polyphenol complexes with a 3:1 polyphenol/nanoSe0 molar ratio were prepared by colloidal selenium nanoparticles (nanoSe0) modified with gallic acid (GA), propyl gallate (PG), and pyrogallic acid (PA), which were spherical with average diameter about 38–77 nm. On this basis, we studied the effect of nanoSe0-polyphenol on the CaC2O4 crystallization and also elaborated the modulation mechanism, which were compared with those for each polyphenol individually. NanoSe0-GA and nanoSe0-PA were easy to induce the formation of calcium oxalate dihydrate (COD) crystals, while nanoSe0-PG induced the formation of quasi-rectangular calcium oxalate monohydrate (COM), multilayered calcium oxalate trihydrate (COT) crystals, and an amount of COD crystals in a dose-dependent fashion by nanoSe0-PG. The strong effect of nanoSe0-polyphenol on the formation of COD and COT crystals could be attributed to electrostatic interaction between nanoSe0-polyphenol and CaC2O4 crystals. The results obtained in the polyphenol system were similar to, as well as different from, nanoSe0-polyphenol because the effect of the polyphenol on the CaC2O4 crystallization could result from not only electrostatic interaction between polyphenols and Ca2+ ions, but also hydrogen bonding interaction between the polyphenols and C2O42– groups. All the obtained COD crystals were thermostable even at 70 °C, while COT crystals were temperature dependent.

In this study, α-TeO2:Ho3+/Yb3+, α-TeO2:Eu3+ and α-TeO2:Ho3+/Yb3+/Eu3+ nanoparticles were prepared via a simple hydrothermal process. The up- and down-conversion properties of the as-prepared nanoparticles were tested at room temperature under a near-infrared photo source (980 nm) and UV-vis photo source, respectively. The results indicated that α-TeO2 NPs were a kind of outstanding host material for both up- and down-conversion luminescence. The α-TeO2:Ho3+/Yb3+ nanoparticles showed sharp up-conversion emission at 545 and 660 nm under 980 nm excitation, ascribed to the 5S2→5I8 and 5F5→5I8 (Ho3+) transitions, and weaker down-conversion emission at 545 nm under 455 nm excitation, ascribed to the 5S2→5I8 (Ho3+) transitions. The α-TeO2:Eu3+ nanoparticles showed strong down-conversion emission at 592 and 615 nm under 395 nm excitation, attributed to the 5D0→7F1 and 5D0→7F2 (Eu3+) transitions. Possessing the advantages of these two luminescent materials, the as-prepared tri-doped samples of α-TeO2:0.5Ho3+/10Yb3+/3Eu3+ (mol.%) nanoparticles could successfully emit visible light via both up- and down-conversion modes.Emission spectra and emission intensity of α-TeO2:xHo3+/10Yb3+/yEu3+ NPs (mol.%) (The serial number (No.) of the vertical axis in (a) and (b) is corresponding to Table 1)(a) Up-conversion emission spectra; (b) Down-conversion emission spectra

This study investigated the effect of colloidal selenium nanoparticles modified with bovine serum albumin (nanoSe0–BSA) on the crystal phase and morphology of CaC2O4 and explained the cooperative inhibition mechanism of nanoSe0 and BSA on the crystallization of CaC2O4. The results were compared with those for nanoSe0 and BSA individually. NanoSe0 could induce the formation of oval or spherical calcium oxalate monohydrate (COM) crystals at high concentrations. BSA could induce the formation of hexagonal plate-shaped COM crystals at low concentrations and the formation of thin diamond-shaped COM crystals and mixed hydrates with cracks at high concentrations. NanoSe0–BSA showed additive effects on CaC2O4 crystal growth. NanoSe0–BSA could induce the formation of mixed hydrates with more surface cracks and obvious voids at relatively low BSA concentrations. These mixed hydrates were considered to be calcium oxalate trihydrate (COT) or calcium oxalate dihydrate (COD) crystals containing BSA or nanoSe0–BSA. These results were a consequence of the interaction of nanoSe0 with BSA. UV–vis, circular dichroism, and FT-IR spectra indicated that the binding of nanoSe0 to BSA induces a change in the secondary structure of BSA and forms the complex. The nanoSe0–BSA binding constant (2.257 × 104 L mol–1) and number of binding sites (1.13) were calculated from the data of fluorescence spectra.

A novel supported nanoadsorbent (nanoSe0-supported/cotton) was prepared by loading selenium nanoparticles with sucrose on absorbent cotton. The feasibility of using nanoSe0-supported/cotton to remove Cu from aqueous solution has been confirmed in batch and continuous systems. Effective experimental parameters such as adsorbent mass, contact time, temperature, initial (feed) Cu(II) concentration, flow rate, and bed height were investigated. The Langmuir adsorption isotherm model was found to accurately fit the batch experimental data (R2 > 0.988) indicating that the adsorption was a monolayer-mode and kinetic data were successfully described by a pseudo-second-order model (R2 > 0.999). For a mass of 0.18 g of nanoSe0-supported/cotton, the maximum Cu removal rate of 0.977 could be achieved with an initial Cu(II) concentration of 0.200 g·L–1 and a contact time of 360 min. After the Cu adsorption, the Se in the nanoSe0-supported/cotton would transform into Cu2Se, and the utilization rate of Se was about 0.817. Continuous systems were investigated in a column. The equilibrium Cu uptake of the column could be determined by the Thomas model at all experimental conditions (ε < 4.3 %). The bed-depth service-time model was applied to predict the service times at 20 %, 40 %, and 60 % breakthrough with a new flow rate and feed concentration.

In vitro antiproliferative effects of selenium nanoparticles (nanoSe0, 10–40 μmol/L) on HeLa (human cervical carcinoma) cells and MDA-MB-231 (human breast carcinoma) cells were examined by optical microscopic inspection and MTT assay in the present study. The nanoSe0 effectively inhibited the growth of MDA-MB-231cells and HeLa cells in a dose-dependent manner. The morphology analysis with atomic force microscope showed that the HeLa cells treated with 10 μmol/L nanoSe0 were rough and shrunken with truncated lamellipodia at terminal part of the cells. Flow cytometric analysis demonstrated that HeLa cells were arrested at S phase of the cell cycle after exposed to nanoSe0 (10 μmol/L). Taken together, our results suggested that nanoSe0 may be more helpful in cancer chemoprevention as a potential anticancer drug.Graphical abstractHighlights► Antiproliferative effects of Se nanoparticles on cancer cells were examined in vitro. ► Se nanoparticles were able to kill the HeLa and MDA-MB-231 cells. ► Se nanoparticles inhibited the growth of HeLa cells via induction of S phase arrest. ► Se nanoparticles may be as a cancer chemopreventive and chemotherapeutic agent.

The formation and characterization of Selenocysteine (SeCys) Self-assembly monolayers (SAMs) was studied. It was found that SeCys SAMs revealed ion-gate response for the electron-transfer of Fe(CN)64-/3- probe ion in the presence of Cu2+ or Pb2+. The ion-gate response of SeCys SAMs resulted from the fact that the interaction between SeCys SAMs and Cu2+ (Pb2+), including the coordination and the electrostatic interaction, changed the conformation of SeCys SAMs.Graphical abstractSelenocysteine Self-assembly monolayers (SeCys SAMs) revealed ion-gate response for the electron-transfer of Fe(CN)64-/3- probe ion in the presence of Cu2+ or Pb2+ ions. It resulted from the conformation change in SeCys SAMs caused by the coordination and the electrostatic interaction.Highlights► Selenocysteine self-assembly monolayers (SeCys SAMs) formed at Au electrode. ► SeCys SAMs revealed ion-gate response for Fe(CN)64-/3- in the presence of Cu2+ or Pb2+. ► The ion-gate response resulted from the conformational change in SeCys SAMs. ► Cu2+ (Pb2+) could interact with SeCys SAMs by electrostatic attraction and coordination.

Different crystal structure of TeO2 nanoparticles were used as the host materials to prepare the Er3+/Yb3+ ions co-doped upconversion luminescent materials. The TeO2 nanoparticles mainly kept the original morphology and phase after having been co-doped the Er3+/Yb3+ ions. All the as-prepared TeO2:Er3+/Yb3+ nanoparticles showed the green emissions (525 nm, 545 nm) and red emission (667 nm) under 980 nm excitation. The green emissions at 525 nm, 545 nm and red emission at 667 nm were attributed to the 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of the Er3+ ions, respectively. For the α-TeO2:Er3+/Yb3+ (3/10 mol%) nanoparticles, three-photon process involved in the green (2H11/2 → 4I15/2) emission, while two-photon process involved in the green (4S3/2→4I15/2) and red (4F9/2 → 4I15/2) emissions. For the β-TeO2:Er3+/Yb3+ (3/10 mol%) nanoparticles, two-photon process involved in the green (2H11/2 → 4I15/2), green (4S3/2 → 4I15/2) and red (4F9/2 → 4I15/2) emissions. It suggested that the crystal structure of TeO2 nanoparticles had an effect on transition processes of the Er3+/Yb3+ ions. The emission intensities of the α-TeO2:Er3+/Yb3+ (3/10 mol%) nanoparticles and β-TeO2:Er3+/Yb3+ (3/10 mol%) nanoparticles were much stronger than those of the (α + β)-TeO2:Er3+/Yb3+ (3/10 mol%) nanoparticles.Highlights► Different crystal structure of TeO2 nanoparticles were used as the host materials to prepare TeO2:Er3+/Yb3+ nanoparticles. ► Upconversion luminescence of TeO2:Er3+/Yb3+ nanoparticles was investigated. ► The emission intensities of α (or β)-TeO2:Er3+/Yb3+ nanoparticles were stronger than those of (α + β)-TeO2:Er3+/Yb3+ nanoparticles.

The removal of copper from aqueous solutions using elemental selenium nanoparticles (nanoSe0) was presented. The uptake of copper by nanoSe0 depended on reducing agents, such as ascorbic acid (Vc) which reduced Cu(II) to Cu(I). The results of scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) indicated that nanoSe0 adsorbed copper by interacting between nanoSe0 and cuprous ions to form copper selenide (Cu2Se) on the surface of nanoSe0. The effects of the mass of nanoSe0, contact time, pH, initial Cu(II) concentration, and temperature on the removal of copper were investigated. The adsorption kinetics was well-described by the pseudosecond-order equation which suggested that the model was indicative of a chemical adsorption mechanism. The adsorption isotherm was better fitted by the Langmuir equation. The maximum adsorption capacity of nanoSe0 for copper was found to be 0.89 g·g–1 at 298.15 K. The nanoSe0 coexisting with Vc was a promising adsorbent for the removal copper ions from aqueous solutions. Moreover, the semiconductor materials Cu2Se could be obtained.

The preparation of tellurium dioxide (TeO2) nanoparticles in a mild condition had been studied. The acid medium, such as gallic acid or acetum was used to prepare the TeO2 nanoparticles at room temperature. The functions of acids were investigated by Nano-ZS, TEM, SEM, FTIR, Raman spectra and XRD. The results showed that the modification and modulation of gallic acid on the TeO2 nanoparticles were stronger than that of acetum. The TeO2 nanoparticles prepared in gallic acid were the orthorhombic phase β-TeO2 spheres in the range of 30–200 nm. The TeO2 nanoparticles prepared in acetum were the tetragonal phase α-TeO2 irregular flakes in the range of 40–400 nm.

Chemical modulation of calcium oxalate (CaC2O4) crystals morphologies by elemental selenium nanoparticles (nanoSe0) was investigated with scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), Fourier transform infrared spectrometry (FTIR), and X-ray diffraction (XRD) analysis. The coordination between nanoSe0 and C2O42− had great effect on the formation of CaC2O4 crystals. NanoSe0 inhibited the growth of calcium oxalate monohydrate (COM) crystals, prevented the aggregation of COM crystals and induced the formation of the spherical calcium oxalate dihydrate (COD) crystals containing selenium, which are the thermodynamically less stable phase and has a weaker affinity to the cell membranes than COM crystals. The inhibition of the crystal growth and aggregation of CaC2O4 crystals by nanoSe0 displayed concentration effects.

Electrochemical oxidation of selenocystine (SeCys) and selenomethionine (SeMet), on a gold electrode was studied by cyclic voltammetry (CV), rotating disk electrode technique (RDE) and chronocoulometry (CC). In 0.2 mol/L HAc-NaAc (pH = 3.90) supporting electrolyte, anodic peak I potential of SeCys and SeMet was 810 mV and 638 mV, respectively, and this electrode process was diffused controlled. The electrochemical oxidation process of SeCys, in which six electron-transfers were involved, yielded selenocystine selenoxide. The electrochemical oxidation process of SeMet, in which two electron-transfers were involved, yielded selemethionine selenoxide.

Surface Ag+ ions forming complexes with the amino (selenoamino) acids compounds have been studied at a silver nitrate-modified carbon paste electrode (AgNO3/CPE). The carboxyl, amidogen and selenium of selenoamino acids could coordinate with Ag+. The coordinating sites of Ag+-SeCys and Ag+-SeMet on electrode surface have been studied in the range of pH value from 1.0 to 12.0. The coordinating sites of Ag+-SeCys and Ag+-SeMet are due to the different configuration and electronegative charge of amino acids in different acidity. Increase of the coordination number of adsorbed species increases the average lifetime of these species on the surface, and hence causes that stronger bonded molecules more effectively prevent the depletion of the surface layer from the Ag+ ions. The voltammetric signals of Ag+-selenoamino acid and Ag+-sulfur-containing amino acid are stronger than those of Ag+-alanine due to the coordinating sites of AgS and AgSe bonds. Moreover, the adsorption of Ag+-selenoamino acid on electrode surface relates to different acidity.