Coordination effect enhanced visualization of latent fingerprint with Eu (TTA)3phen-SiO2 microspheres.

Latent fingerprint (LFP) powders are crucial in the detection of LFPs in forensic science. However, it is often plagued by poor image resolution and low contrast. Herein, enhanced LFP fluorescence (FL) visualizations are achieved by doping Eu(III) coordination compound Eu(TTA)3phen directly into SiO2 microspheres instead of Eu(III) ions. Using the synthesized Eu(TTA)3phen-SiO2 microspheres, the fine characteristic structure of LFP can be seen and recognized under 365 nm irradiation, up to Level 3. However, the Eu3+-SiO2 microspheres were difficult to recognize the Level 2,3 fingerprint structure. The difference between the ridge and furrow gray values of Eu(TTA)3phen-SiO2 microspheres is 2.1 times that of Eu3+-SiO2 microspheres. The coordination effect increased the asymmetry around Eu(III) ions, resulting in the ultrasensitive 5D0→7F2 transition, thus increasing the FL intensity, and the uniform doping of the Eu(III) coordination compound into SiO2 also reduced the surface FL quenching due to shielding from oxygen. Under this dual effect, the LFP performance of Eu(TTA)3phen-SiO2 microspheres has been significantly improved. We believe that this novel and easy LFP visualization method is a promising routine in specific target detection including criminal investigation, customhouse check-in, and drug control.

Photocatalytic Simultaneous Removal of Nitrite and Ammonia via a Zinc Ferrite/Activated Carbon Hybrid Catalyst under UV-Visible Irradiation.

Nitrite and ammonia often coexist in waters. Thus, it is very significant to develop a photocatalytic process for the simultaneous removal of nitrite and ammonia. Herein, zinc ferrite/activated carbon (ZnFe2O4/AC) was synthesized and characterized by X-ray diffraction spectroscopy, transmission electron microscopy, Raman spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The valence band level of ZnFe2O4 was measured by X-ray photoelectron spectroscopy-valence band spectroscopy, and first-principles calculation was performed to confirm the band structure of ZnFe2O4. The as-synthesized ZnFe2O4/AC species functioned as a photocatalyst to simultaneously remove nitrite and ammonia under anaerobic conditions upon UV-visible light irradiation at the first stage. The results indicated that an average removal ratio of 92.7% with ±0.2% error for nitrite degradation for three runs was achieved in 50.0 mg/L nitrite + 100.0 mg/L ammonia solution with pH 9.5 under anaerobic conditions for 3 h at this stage; simultaneously, the removal ratio of 64.0% with ±0.2% error for ammonia was also achieved. At the second stage, oxygen gas was bubbled in the reactor to photocatalytically eliminate residual ammonia under aerobic conditions upon continuous irradiation. The results demonstrated that the removal ratios for nitrite, ammonia, and total nitrogen reached to 92.0, 90.0, and 90.2% at 12th hour, respectively, and the product released during photocatalysis is N2 gas, detected by gas chromatography, fulfilling the simultaneous removal of nitrite and ammonia. The reaction mechanism was exploited.

Near-Infrared-Driven Selective Photocatalytic Removal of Ammonia Based on Valence Band Recognition of an α-MnO2/N-Doped Graphene Hybrid Catalyst.

Near-infrared (NIR)-response photocatalysts are desired to make use of 44% NIR solar irradiation. A flower-like α-MnO2/N-doped graphene (NG) hybrid catalyst was synthesized and characterized by X-ray diffraction spectroscopy, transmission electron microscopy, Raman spectroscopy, UV-vis-NIR diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. The flower-like material of α-MnO2/NG was oval-shaped with the semi major axis of 140 nm and semi minor axis of 95 nm and the petal thickness of 3.5-8.0 nm. The indirect band gap was measured to be 1.16 eV, which is very close to 0.909 eV estimated by the first-principles calculation. The band gap can harvest NIR irradiation to 1069 nm. The coupling of α-MnO2 with NG sheets to form α-MnO2/NG can significantly extend the spectrum response up to 1722 nm, improving dramatically the photocatalytic activity. The experimental results displayed that the α-MnO2/NG hybrid catalyst can recognize ammonia in methyl orange (MO)-ammonia, rhodamine B (RHB)-ammonia, and humic acid-ammonia mixed solutions and selectively degrade ammonia. The degradation ratio of ammonia reached over 93.0% upon NIR light irradiation in the mixed solutions, while those of MO, RHB, and humic acid were only 9.7, 9.4, and 15.7%, respectively. The products formed during the photocatalytic process were followed with ion chromatography, gas chromatography, and electrochemistry. The formed nitrogen gas has been identified during the photocatalytic process. A valence band recognition model was suggested based on the selective degradation of ammonia via α-MnO2/NG.

Photocatalytic reduction of CO2 based on a CeO2 photocatalyst loaded with imidazole fabricated N-doped graphene and Cu(ii) as cocatalysts.

Cocatalysts are vital for improving photocatalytic activity. Incorporating nitrogen atoms on a graphene frame using an imidazole cycle resulted in a new N-doped graphene (denoted as ING). Cerium(iv) oxide (CeO2) nanoparticles were dispersed on ING sheets, producing an ING/CeO2 hybrid material. The ING/CeO2 hybrid material was characterized using X-ray diffraction, transmission electron microscopy, Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy and surface photovoltage spectroscopy. Copper(ii) ions [Cu(ii)] were adsorbed on the ING/CeO2 hybrid material to directly form Cu(ii)/ING/CeO2, which could capture the photogenerated electrons to reduce carbon dioxide (CO2) to methanol (CH3OH) under incident light irradiation. The results showed that the yield from reducing CO2 to CH3OH during the photocatalytic process using Cu(ii)/ING/CeO2 as the photocatalyst approached 385.8 µmol g-1 cat. h-1, whereas the yield was only 3.57 µmol g-1 cat. h-1 using ING/CeO2 as the photocatalyst. This shows that the Cu(ii) ions play a vital role during photocatalytic reduction of CO2 by forming copper(i) ions [Cu(i)]. The percentage of ING in the ING/CeO2 hybrid material was investigated, and the results indicated that 3.6% of ING achieved an optimal yield of CH3OH during the photo-reduction process. The simultaneous roles of Cu(ii) ions and ING sheets demonstrate a synergistic strategy for improving the photocatalytic CO2 reduction.

Graphene sheet-starch platform based on the groove recognition for the sensitive and highly selective determination of iodide in seafood samples.

The functionalization of graphene nanosheets was realized using a simple starch mixture to achieve a highly selective recognition of iodide, thereby surmounting the complicated reactions possibly leading to low yield during functionalization. The groove recognition for starch to iodide, a novel recognition model, was established. The starch-to-graphene nanosheet mass ratio of 3:2 produced an optimal current signal. The recognition and measurement procedures were conducted in different cells, respectively. These procedures improved the selectivity and sensitivity, and overcame the possibility of interference from coexisting ions. Under optimal conditions, the graphene sheet-starch electrode was immersed in a recognition cell at pH 2.0 for 10min, afterward, in a measurement cell at pH 1.0 for quantitative analysis, resulting in the highest current signals obtained. The quantitative electrochemical measurements yielded a mean value of 214.6mg/kg in actual samples of commercially available seafood sample, whereas the spectrophotometric measurements produced a mean value of 226.7mg/kg. If the spectrophotometric value for the seafood sample is accurate, the percentage error for the electrochemical method is only 5.3%. Therefore, the electrochemical method is reliable for qualitative iodide measurements. The groove recognition was highlighted to elucidate the specific selectivity.

Effect of alkali cations on heterogeneous photo-Fenton process mediated by Prussian blue colloids.

This article evaluates Prussian blue (iron hexacyanoferrate) colloids as a heterogeneous photo-Fenton catalyst for the degradation of Rhodamine B. The emphasis is laid on the effects of alkali metal cations on the photo-Fenton process. The facts show that alkali cations strongly affect the degradation rate of organic species. The degradation rates of Rhodamine B, Malachite Green, and Methyl Orange in the presence of KCl, KNO(3), and K(2)SO(4), respectively, are faster than their degradation rates in the presence of the corresponding sodium salts. The average degradation rates of Rhodamine B in 0.2 M KCl, NaCl, RbCl, and CsCl solution, decline in sequence, and the rate in KCl solution is greater than that without any salt added deliberately. Thus, potassium ions accelerate the degradation rate, but sodium, rubidium, and cesium ions slow the rate. The order of the rates is R(K)>R>R(Na)>R(Rb)>R(Cs), which is consistent with that of the voltammetric oxidation currents of Prussian blue in the corresponding cation solutions. This phenomenon is attributed to the molecular recognition of the microstructure in Prussian blue nanoparticles to the alkali cations. The reaction mechanism of the photo-Fenton process has also been explored.

Electrochemical and ultraviolet-visible spectroscopic studies on the interaction of deoxyribonucleic acid with vitamin B6.

Studies on the interaction of DNA with vitamin B(6) were carried out with a DNA-modified electrode by electrochemistry and Ultraviolet-visible spectroscopy. The results showed that there exists the supra-molecule interaction between base groups on DNA and vitamin B(6) by forming hydrogen binding, the binding equilibrium constant of the interaction is equal to 115.3 M(-1), the binding ratio of nucleotide to vitamin B(6) is 5:1. Based on the electrochemical and Ultraviolet-visible spectrum studies the interaction mode of DNA with vitamin B(6) was explored.

A reversible adsorption-desorption interface of DNA based on nano-sized zirconia and its application.

It is essential for the information storage in DNA-based bio-chips to construct a reversible exchange interface of DNA. Here, a highly reproducible and reversible adsorption-desorption interface of DNA based on the nano-sized zirconia in different pH solution was successfully fabricated. The results showed that DNA can be adsorbed onto the nano-sized zirconia from its solution, and can desorb from the nanoparticles in 0.10 M KOH solution. When the matrix with nanoparticles returns to the DNA solution again, DNA can be re-adsorbed onto them as initial state. Moreover, the interaction of DNA with non-electroactive molecules, 2,2'-bipyridine, has been studied by electrochemistry method in the aid of probe Co(phen)(3)(3+). The experiments showed that when 2,2'-bipyridine was added into the test solution, the voltammetric peak currents of Co(phen)(3)(3+) decreased; and the decrease value of peak current against the concentration of 2,2'-bipyridine has a good Langmuir relationship, by which the equilibrium constant of interaction between 2,2'-bipyridine and DNA was estimated to be 1.57 x 10(4)M(-1).

ZrO(2) gel-derived DNA-modified electrode and the effect of lanthanide on its electron transfer behavior.

A new method of immobilizing deoxyribonucleic acid (DNA) was developed based on sol-gel technique, the resulting DNA-modified electrode was characterized with the cyclic voltammetry. The electrode was used to study the electron transfer of DNA in 1.0 mM potassium ferricyanide system in different concentrations of lanthanum(III), europium(III), and calcium(II). The heterogeneous rate constants of the reduction of Fe(CN)(6)(3-) with and without the above cations were calculated by Tafel equation. The results show that lanthanide ions can increase the electron transfer rate much more than calcium ion.