Preparation of 4-Amino-3-hydrazino-1,2,4-triazol-5-thiol-Modified Graphene Oxide and Its Greatly Enhanced Selective Adsorption of Gallium in Aqueous Solution.

Efficient recovery of gallium (Ga) from vanadium slag processing residue (VSPR) solution is of great significance for environmental protection and resource utilization, but improving its selective adsorption against the coexisting Sc3+ and In3+ is still challenging. Herein, a novel adsorbent consisting of 4-amino-3-hydrazino-1,2,4-triazol-5-thiol (AHTZT)-modified graphene oxide (GO-AHTZT) was successfully synthesized that exhibits a higher adsorption selectivity for Ga3+ in VSPR solution with coexisting Sc3+ and In3+. Under optimal conditions, the adsorption capacity of GO-AHTZT for Ga3+ can reach 23.92 mg g-1, which is 4.9 and 12.6 times higher than that for Sc3+ (4.87 mg g-1) and In3+ (1.90 mg g-1) adsorption, indicating the excellent anti-interference ability of GO-AHTZT against Sc3+ and In3+. The process and mechanism of Ga3+ adsorption onto GO-AHTZT was also studied and discussed in detail. By measuring the adsorption process and by characterizing the adsorbent before and after adsorption, we demonstrate that the selective interaction between the Ga3+- and N-containing groups in AHTZT is the main reason for the improved adsorption selectivity. This work opens up an avenue for the design and synthesis of highly selective adsorbents for Ga3+ in complex VSPR solutions.

Bismuth-Decorated Honeycomb-like Carbon Nanofibers: An Active Electrocatalyst for the Construction of a Sensitive Nitrite Sensor.

The existence of carcinogenic nitrites in food and the natural environment has attracted much attention. Therefore, it is still urgent and necessary to develop nitrite sensors with higher sensitivity and selectivity and expand their applications in daily life to protect human health and environmental safety. Herein, one-dimensional honeycomb-like carbon nanofibers (HCNFs) were synthesized with electrospun technology, and their specific structure enabled controlled growth and highly dispersed bismuth nanoparticles (Bi NPs) on their surface, which endowed the obtained Bi/HCNFs with excellent electrocatalytic activity towards nitrite oxidation. By modifying Bi/HCNFs on the screen-printed electrode, the constructed Bi/HCNFs electrode (Bi/HCNFs-SPE) can be used for nitrite detection in one drop of solution, and exhibits higher sensitivity (1269.9 µA mM-1 cm-2) in a wide range of 0.1~800 µM with a lower detection limit (19 nM). Impressively, the Bi/HCNFs-SPE has been successfully used for nitrite detection in food and environment samples, and the satisfactory properties and recovery indicate its feasibility for further practical applications.

In Situ Derived Bi Nanoparticles Confined in Carbon Rods as an Efficient Electrocatalyst for Ambient N2 Reduction to NH3.

Electrocatalytic N2 reduction is deemed as a prospective strategy toward low-carbon and environmentally friendly NH3 production under mild conditions, but its further application is still plagued by low NH3 yield and poor faradaic efficiency (FE). Thus, electrocatalysts endowing with high activity and satisfying selectivity are highly needed. Herein, Bi nanoparticles in situ confined in carbon rods (Bi NPs@CRs) are reported, which are fabricated via thermal annealing of a Bi-MOF precursor as a high-efficiency electrocatalyst for artificial NH3 synthesis with favorable selectivity. Such an electrocatalyst conducted in 0.1 M HCl achieves a high FE of 11.50% and a large NH3 yield of 20.80 µg h-1 mg-1cat. at -0.55 and -0.60 V versus reversible hydrogen electrode, respectively, which also possesses high electrochemical durability.

Nanostructured Bromide-Derived Ag Film: An Efficient Electrocatalyst for N2 Reduction to NH3 under Ambient Conditions.

Electrochemical reduction has been regarded as a sustainable strategy to tackle energy-intensive operations by the Haber-Bosch process achieving catalytic conversion of N2 to NH3 under mild conditions. However, the challenge of N2 electroconversion emphasizes the requirement of efficient electrocatalysts. In this paper, we report the development of porous bromide-derived Ag film (BD-Ag/AF) as an efficient electrocatalyst for N2 reduction reaction. During electrochemical test, Br- anions are released and adsorbed onto the surfaces of the electrode, suppressing hydrogen evolution reaction. Such BD-Ag/AF shows a high Faradaic efficiency of 7.36% at -0.6 V vs reversible hydrogen electrode in 0.1 M Na2SO4, which is higher than that (0.38%) of porous Ag film without Br- anions. Moreover, it exhibits excellent long-term electrochemical durability.

Facilitating Active Species Generation by Amorphous NiFe-Bi Layer Formation on NiFe-LDH Nanoarray for Efficient Electrocatalytic Oxygen Evolution at Alkaline pH.

Searching for a simple and fast strategy to effectively enhance the oxygen evolution reaction (OER) performance of non-noble-metal electrocatalysts in alkaline media remains a significant challenge. Herein, the OER activity of NiFe-LDH nanoarray on carbon cloth (NiFe-LDH/CC) in alkaline media is shown to be greatly boosted by an amorphous NiFe-Borate (NiFe-Bi ) layer formation on NiFe-layered double hydroxide (NiFe-LDH) surface. Such a NiFe-LDH@NiFe-Bi /CC catalyst electrode only needs an overpotential of 294 mV to drive 50 mA cm-2 in 1.0 m KOH; 116 mV less than that needed by NiFe-LDH/CC. Notably, this electrode also demonstrates strong long-term electrochemical durability. The superior activity is ascribed to the pre-formed amorphous NiFe-Bi layer effectively promoting active species generation on the NiFe-LDH surface. This work opens up exciting new avenues for developing high-performance water-oxidation catalyst materials for application.

Surface Modification of a NiS2 Nanoarray with Ni(OH)2 toward Superior Water Reduction Electrocatalysis in Alkaline Media.

Interface engineering has been demonstrated to be effective in promoting hydrogen evolution reaction (HER) in an alkaline solution. Herein, we report that the HER activity of a NiS2 nanoarray on a titanium mesh (NiS2/TM) in alkaline media is greatly boosted by the electrodeposition of Ni(OH)2 onto NiS2 [Ni(OH)2-NiS2/TM]. Ni(OH)2-NiS2/TM only needs an overpotential of 90 mV to deliver 10 mA cm-2 in 1.0 M KOH. Density functional theory calculations confirm that Ni(OH)2-NiS2 has a lower water dissociation free energy and a more optimal hydrogen adsorption free energy than NiS2.

Ultrastrong Chemiluminescence Activity of Nanocarbon Materials after Ozonation and Their Effects on Different Chemiluminescent Systems.

Ozonized nanocarbon materials with different dimensionalities, structures, and components exhibited significantly different chemiluminescence (CL) activities. The ozonation time and the weight ratio of hydroxyl carbon nanotubes (d≈8 nm, hyCNTs-8) and graphene oxide (GO) strongly affected the CL activity of ozonized hybrids. Among GO, hyCNTs-8, and GO/hyCNTs-8, the GO/hyCNTs-8 hybrids exhibited the strongest CL-enhancing properties toward the luminol/H2 O2 system, in contrast to previous reports. This study provides new understanding of the CL activity and CL-enhancing properties of nanocarbon materials in signal-enhanced analytical and biomedical fields.

Synthesis of "amphiphilic" carbon dots and their application for the analysis of iodine species (I2, I(-) and IO3(-)) in highly saline water.

"Amphiphilic" carbon dots (A-CDs) with a strong green fluorescence emission were synthesized by a simple and green method at room temperature. The characterization demonstrated that the synthesized A-CDs have both hydrophilic and hydrophobic properties and could be dispersed well in aqueous and organic solutions. As a fluorescent probe, the fluorescence of A-CDs could be obviously quenched in the presence of iodine (I2) and the quenching rate is proportional to the concentration of I2. Therefore, the A-CDs could be used as fluorophores for the detection of I2 with higher selectivity and sensitivity, and the linear working range for the I2 sensor is 80 nM-10 µM with a detection limit of 3.5 nM (S/N = 3). More interesting is that IO3(-) and I(-) could be transformed to I2 with different sample treatment processes, therefore, the I2 sensor based on A-CDs could also be used for the analysis of iodine species (I2, I(-) and IO3(-)) in samples. The possible mechanism has also been discussed in this work, and the high selectivity response to I2 can be attributed to the amphiphilic properties of A-CDs, which bring I2 closer to A-CDs and quench their fluorescence. The proposed I2 sensor has been successfully used for the analysis of iodine species in highly saline water, and the satisfactory results of detection and analysis of iodine species in samples demonstrate that the developed I2 sensor based on A-CDs has potential application in the fields of environment and clinical medicine.

A novel dual-switch fluorescent probe for Cr(III) ion based on PET-FRET processes.

Two different strategies for photoinduced electron transfer (PET) and fluorescence resonance energy transfer (FRET) have been designed and combined into one sensing system. The novel probe NNRhB was developed based on 1,8-naphthalimide and rhodamine moieties, in which two fluorophores are sensitive to the presence of Cr(3+) in different chromium ion concentration regimens. Therefore, the proposed sensing system represents dual-switch states and segmented detection behavior, with the fluorescence emission color spans from green to orange over an increasing Cr(3+) concentration gradient. When excited in the visible region, the initial emission band at 537 nm was enhanced. That was attributed to the suppression of the PET process, which arose from Cr(3+)-coordination with a 1,8-naphthalimide derivative. At a sufficiently high concentration of Cr(3+) (over 9 µM), the spirolactam rhodamine component in NNRhB converted to the opened form as a result of Cr(3+) coordination, which turned the emission color from green to orange via FRET. The fluorescence phenomena of the compound 1 and compound 2 split from compound NNRhB confirm our hypothesis of the spectral response mechanisms. Moreover, compared with a single fluorescent response in compound 1 or compound 2, the dual-switch fluorescent probe NNRhB shows a more sensitive and distinct visual detection ability for Cr(3+) ions. This probe affords a high selectivity and sensitivity to Cr(3+) from 30 nM to 80 µM; the detection limit was 0.14 nM. The results of practical application experiments suggest that the Cr(3+)-selective ligand prepared here may provide an effective strategy for detection of Cr(3+) in environmental and biological applications.

High-efficiency electrocatalytic nitrite-to-ammonia conversion on molybdenum doped cobalt oxide nanoarray at ambient conditions.

Electrochemical conversion of nitrite (NO2-) contaminant to green ammonia (NH3) is a promising approach to achieve the nitrogen cycle. The slow kinetics of the complex multi-reaction process remains a serious issue, and there is still a need to design highly effective and selective catalysts. Herein, we report that molybdenum doped cobalt oxide nanoarray on titanium mesh (Mo-Co3O4/TM) acts as a catalyst to facilitate electroreduction of NO2- to NH3. Such a catalyst delivers an extremely high Faradaic efficiency of 96.9 % and a corresponding NH3 yield of 651.5 µmol h-1 cm-2 at -0.5 V with strong stability. Density functional theory calculations reveal that the introduction of Mo can induce the redistribution of electrons around Co atoms and further strengthen the adsorption of NO2-, which is the key to facilitating the catalytic performance. Furthermore, the assembled battery based on Mo-Co3O4/TM suggests its practical application value.

Anodic electrogenerated chemiluminescence behavior of graphite-like carbon nitride and its sensing for rutin.

In this paper, the anodic electrogenerated chemiluminescence (ECL) behavior of graphite-like carbon nitride (g-C3N4) is studied using cyclic voltammetry with triethanolamine (TEA) as a coreactant. The possible anodic ECL response mechanism of the g-C3N4/TEA system is proposed. Furthermore, it is observed that the anodic ECL signal can be quenched efficiently in the presence of rutin, on the basis of which a facile anodic ECL senor for the determination of rutin is developed. This ECL sensor is found to have a linear response in the range of 0.20-45.0 µM and a low detection limit of 0.14 µM (at signal-to-noise of 3). These results suggest that semiconductor g-C3N4 has great potential in extending the application in the ECL field as an efficient luminophore.

Facile synthesis of functionalizated carbon nanospheres for determination of Cu2+.

In this research, quantities of carbon nanospheres (CNSs) were prepared with a convenient and low cost method at atmospheric pressure and functionalized with the xanthate group in a simple way. The materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectra (FT-IR), and X-ray photoelectron spectroscopy (XPS). In addition, the carbon nanospheres (CNSs) xanthate was applied to fabricate a modified carbon paste electrode (CPE) for the selective and sensitive determination of Cu(2+). Also, the xanthate with a -CS2 group was applied as a chelating agent to enrich Cu(2+) in the determination of Cu(2+) ions. In square wave stripping voltammetry (SWSV), the carbon nanospheres xanthate-modified CPE displayed linear response to Cu(2+) in the concentration range of 8.0 × 10(-8) M to 2.2 × 10(-6) M with a detection limit (S/N = 3) of 3.55 × 10(-8) M. The modified electrode exhibited excellent analytical performance in terms of high repeatability. Finally, it was applied to detect Cu(2+) in the wastewater samples with high accuracy and good recovery, indicating its promising application in the routine analysis of metal ions.

Large enhancement of oscillating chemiluminescence with [Ru(bpy)3 ](2+) -catalyzed Belousov-Zhabotinsky reaction in the presence of tri-n-propylamine.

Oscillating chemiluminescence enhanced by the addition of tri-n-propylamine (TPrA) to the typical Belousov-Zhabotinsky (BZ) reaction system catalyzed by ruthenium(II)tris(2.2'-bipyridine)(Ru(bpy)3 (2+) ) was investigated using a luminometry method. The [Ru(bpy)3 ](2+) /TPrA system was first used as the catalyst for a BZ oscillator in a closed system, which exhibited a shorter induction period, higher amplitude and much more stable chemiluminescence (CL) oscillation. The effects of various concentrations of TPrA, oxygen and nitrogen flow rate on the oscillating behavior of this system were examined. In addition, the CL intensity of the [Ru(bpy)3 ](2+) /TPrA-BZ system was found to be inhibited by phenol, thus providing a way for use of the BZ system in the determination of phenolic compounds. Moreover, the possible mechanism of the oscillating CL reaction catalyzed by [Ru(bpy)3 ](2+) /TPrA and the inhibition effects of oxygen and phenol on this oscillating CL system were considered.

3D cauliflower-like Ni foam: a high-efficiency electrocatalyst for ammonia production via nitrite reduction.

A 3D cauliflower-like Ni foam on titanium plate (Ni foam/TP) shows high electrocatalytic performance for ambient ammonia (NH3) synthesis via nitrite (NO2-) reduction. In 0.1 M phosphate-buffered saline solution with 0.1 M NO2-, such Ni foam/TP attains a high NH3 Faradaic efficiency (FE) of 95.9% and a large NH3 yield of 742.7 µmol h-1 cm-2 at -0.8 V. Its Zn-NO2- battery offers a high power density of 6.2 mW cm-2 and an NH3 FE of 90.1%.

Electrogenerated chemiluminescence behavior of graphite-like carbon nitride and its application in selective sensing Cu2+.

This paper reports for the first time the electrogenerated chemiluminescence (ECL) behavior of graphite-like carbon nitride (g-C(3)N(4)) with K(2)S(2)O(8) as the coreactant. The possible ECL reaction mechanisms are proposed. The spectral features of the ECL emission and photoluminescence (PL) of g-C(3)N(4) are compared, and their resemblance demonstrates that the excited states of g-C(3)N(4) from both ECL and photoexcitation are the same. The effects of K(2)S(2)O(8) concentration, pH, g-C(3)N(4)/carbon powder ratio, and scan rate on the ECL intensity have been studied in detail. Furthermore, it is observed that the ECL intensity is efficiently quenched by trace amounts of Cu(2+). g-C(3)N(4) is thus employed to fabricate an ECL sensor which shows high selectivity to Cu(2+) determination. The limit of detection is determined as 0.9 nM. It is anticipated that g-C(3)N(4) could be a new class of promising material for fabricating ECL sensors.

High-Efficiency Electrochemical Nitrate Reduction to Ammonia on a Co3O4 Nanoarray Catalyst with Cobalt Vacancies.

Electrocatalytic nitrate reduction reaction (NO3RR) affords a bifunctional character in the carbon-free ammonia synthesis and remission of nitrate pollution in water. Here, we fabricated the Co3O4 nanosheet array with cobalt vacancies on carbon cloth (vCo-Co3O4/CC) by in situ etching aluminum-doped Co3O4/CC, which exhibits an excellent Faradaic efficiency of 97.2% and a large NH3 yield as high as 517.5 µmol h-1 cm-2, better than the pristine Co3O4/CC. Theoretical calculative results imply that the cobalt vacancies can tune the local electronic environment around Co sites of Co3O4, increasing the charge and reducing the electron cloud density of Co sites, which is thus conducive to adsorption of NO3- on Co sites for greatly enhanced nitrate reduction. Furthermore, the vCo-Co3O4 (311) facet presents excellent NO3RR activity with a low energy barrier of about 0.63 eV on a potential-determining step, which is much smaller than pristine Co3O4 (1.3 eV).

In situ synthesis of gold nanoparticles on porous polyacrylonitrile nanofibers for sensing applications.

A simple and cost-effective method was reported to synthesize small size (6 nm) gold nanoparticles (AuNPs) on polyacrylonitrile (PAN) electrospun nanofibers (AuNPs/PAN). The formation of AuNPs is attributed to the in situ reduction of Au(III) to Au(0) by 4-(dimethylamino)benzaldehyde doped in the PAN nanofibers. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) confirmed that the AuNPs/PAN nanofibers showed good conductivity. The AuNPs/PAN nanofibers were used to immobilize tris(2,2'-bipyridyl)ruthenium(II) ions (Ru(bpy)(3)(2+)) to form an electrochemiluminescence (ECL) sensor. The AuNPs on the PAN nanofibers exhibited an excellent catalytic effect on the ECL of Ru(bpy)(3)(2+) which could be employed to detect low concentrations of phenolic compounds. The linear response range of the ECL sensor to hydroquinone is 0.55-37 µM with limit of detection of 80 nM (S/N = 3). This sensor has been successfully applied to determine the hydroquinone content in photographic developer samples. Our work provides a very simple and cost-effective method to synthesize AuNPs on polymer nanofibers which shows great potential in the field of electrocatalysis and chemo/biosensors.

Organic carbon dot coating for superhydrophobic aluminum alloy surfaces.

A novel fluorine-free and silicon-free superhydrophobic aluminum alloy (treated-Al) is fabricated by chemical etching using hydrochloric acid and hydrogen peroxide and modified with an organic carbon dot (OCD) coating. The water contact angle (CA) of the treated-Al surface increases with the OCD concentration. When etched aluminum (etched-Al) is modified with 0.5 mg/ml OCDs, a CA of 161.4° is achieved, which indicates good nonwettability. SEM results verify that porous microstructures with cavities are uniformly distributed on the surface of etched-Al, in contrast to the bare aluminum alloy, which forms a primary rough structure. After treatment with 0.5 mg/ml OCDs, a nanoparticle coating is dispersed on the rough structures of treated-Al-0.5, which can trap air and make a water droplet essentially rest on a layer of air. The treated-Al-0.5 material has good self-cleaning properties and can sweep away contaminants at both 20 and 0°C. The Ecorr and Icorr of treated-Al-0.5 are - 0.56 V and 2.82 × 10-6 A/cm2, respectively, which shows good anticorrosion performance.

Dual-readout performance of Eu3+-doped nanoceria as a phosphatase mimic for degradation and detection of organophosphate.

Eu3+-Doped nanoceria (Eu:CeO2) with self-integrated catalytic and luminescence sensing functions was synthesized by a simple and gentle one-pot method to build a dual-readout nanozyme platform for organophosphate compound (OPC) sensing in this work. The catalytic degradation of the model substrate of OPC, p-nitrophenyl phosphate (p-NPP), by as-prepared Eu:CeO2 can be completed in 2 min with little influence of temperature and pH values, highlighting the advantages of Eu:CeO2 as an artificial enzyme for dephosphorylation. Most importantly, the characteristic red emission of Eu3+ (592 nm) from Eu:CeO2 can be quenched by p-NPP, accompanied by a color change from colorless to yellow. Based on this, linear ranges of 4-50 µM with a detection limit of 3.3 µM and 1-20 µM with a detection limit of 0.6 µM for p-NPP were obtained by colorimetric and fluorescence methods, respectively. Furthermore, the fluorescence strategy was effectively applied to the determination of ethyl para-nitrophenyl (EPN), one of the most commonly used pesticides, with a detection limit of 5.86 µM. The proposed strategy was also successfully applied to the assay of p-NPP and EPN in real water samples, showing great application prospects in detecting OPC in the environment.

Silicon nanoparticles-based ratiometric fluorescence platform: Real-time visual sensing to ciprofloxacin and Cu2.

In this work, a silicon nanoparticles (Si NPs)-based ratiometric fluorescence sensing platform was conveniently fabricated by simply mixing fluorescent Si NPs as co-ligands and reference signal with lanthanide metal ion Eu3+ as response signal. The introduction of ciprofloxacin (CIP) remarkably turned on the characteristic fluorescence of Eu3+ at 590 nm and 619 nm through the "antenna effect". At the same time, the blue emission of Si NPs at 445 nm kept comparatively stable. A good linear relationship between the ratio fluorescence intensity and CIP concentration in the range of 0.211-132.4 µM with a limit of detection (LOD) of 89 nM was obtained. In the presence of Cu2+, the fluorescence emission of Eu3+ was sharply turned off because of the stronger coordination ability of Cu2+ with CIP, which guaranteed the sequential detection of Cu2+. Meanwhile, the distinct fluorescent color change from bright blue to red, then back to blue, enabled naked-eye visual detection of CIP and Cu2+ in the solution phase and on paper-based test strip, and was successfully applied to determine the levels of CIP in complicated food samples with high sensitivity.