In this work, a photoelectrochemical (PEC) sensing system was developed for chemical detection without any tags. The system is based on methylammonium lead iodide chloride perovskite as the photoelectrochemical signal-generating molecule, tin oxide nanoparticles (SnO2) as the electron transport layer, and ionic liquid of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) as the stabilizer and electrolyte. The photosensitizer film is formed through spin-coating followed by low-temperature sintering. Upon irradiation with 473 nm light, an anodic photocurrent is generated in a blank electrolyte and changed significantly after addition of hemin into the electrolyte. The change of photocurrent after addition of hemin suggested that the chemicals participated in a photoelectrochemical process. Our work paves the way to developing analytical methods with perovskite.Topics: Electric transport processes and properties; Nanoparticles; Phase; Sensors; Sensors; Solid state electrochemistry;

Metal surfaces with a hydrophobic feature, which could prevent percolation of water droplets and improve their resistance against corrosion, have attracted extensive interest. In this work, we demonstrated a method to prepare a hydrophobic copper surface by coating polydopamine (PDA), and modifying with 1-dodecanethiol (1-DT). Surface hydrophobicity was evaluated by contact angle analysis. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), near infrared (NIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to understand the structure and composition of the resultant coating at the metal surface. The inhibition efficiency of the optimal hydrophobic surface in 3 wt% NaCl aqueous solution, explored by using electrochemical measurements, was 95.3%, which was due to synergy effects of PDA and 1-DT. The promising inhibition of copper corrosion was also validated by scanning electron microscopy observation.

Alumina is widely recognized as chemically inert, and resistant to oxidation and high temperature. In this study, Au/Al2O3 nanocomposites (NCs) were prepared by a facile method and were used as a surface enhanced Raman scattering (SERS) substrate for detection of adenosine triphosphate (ATP). This Au/Al2O3-based SERS substrate demonstrated good sensitivity with the lowest detectable concentration of 5 × 10−9 M for ATP and a good linear relationship ranging from 5 × 10−5 to 5 × 10−9 M. The strategy of improvement of SERS detection sensitivity for ATP was based on the consideration of ATP captured by such SERS substrate via chelation of aluminum and phosphates, which was validated by X-ray photoelectron spectroscopy. In addition, alumina as a supporting material could be expected to prolong the stability of such a SERS substrate.

•A new strategy was used to make Au nanoparticles dotted magnetic sheets (Au-MGS).•Au-MGS exhibited a long-shelf-time about 4 months at ambient condition.•The proposed SERS assay detects trace SCN− in milk and SCN− in saliva from smoker.Abuse of thiocyanate (SCN−) in food products results in the people’s health risks. Detection of SCN− residue in milk and infant formula calls for rapid and sensitive analytical protocols. In this work, Au nanoparticles dotted magnetic sheets (Au-MGS) with the help of inositol hexakisphosphate (IP6) were used as surface enhanced Raman scattering (SERS) substrate for sensitively detecting trace SCN− in milk. Since IP6 served as binding and stable agent to chelate with metal ions, the Au-MGS represented uniformity and stability as well as the well-dispersive Au nanoparticles. As a result, the limit of detection (LOD) reached 10−8 g/L. Additionally, with aiding by an external magnet inducing, Au-MGS substrate further presented improved SERS activity. By using a portable Raman spectrometer, such Au-MGS based SERS assay could be expected to be used for in situ detection of SCN− in milk on markets as well as for determination of SCN− in saliva from the smoker.Figure optionsDownload full-size imageDownload high-quality image (172 K)Download as PowerPoint slide

•Cu2O/Pd with network structure was synthesized using CuO nanorods as reaction beds.•Cu2O/Pd had the remarkably enhanced electrocatalytic activity for methanol oxidation.•Cu2O/Pd exhibited superior CO-tolerance and reasonable stability.The CuO nanorods (NRs) are prepared with the help of inositol hexakisphosphate which serves as a binding agent and stabilizer. We have successfully fabricated Cu2O-decorated palladium networks (Cu2O/Pd Networks) by using such CuO NRs as reaction beds. Transmission electron microscopy images show that Cu2O/Pd network is composed of small and irregular fused nanoparticles with an average size of about 10 nm. Electrochemical results depict that the as-synthesized catalyst exhibits 2-fold higher activity for methanol oxidation than the commercially available 20% Pd/C catalyst and Pd black catalyst. Furthermore, CO-tolerance is also remarkably enhanced due to the presence of Cu2O. Such highly active, low-cost, and superiorly CO-tolerant catalysts of Cu2O/Pd Networks will open up a new avenue for direct methanol fuel cells.

ssDNA was employed to readily disperse reduced graphene oxide (RGO) to form ssDNA–RGO composites, which could be used as a superior support to expediently electrodeposit Pt to synthesize ssDNA–RGO/cotton-flower-like-Pt nanocomposites (ssDNA–RGO/cf-Pt). The formation of cotton-flower-like-Pt clusters was due to the assistance of nitrogen atoms and phosphate groups in ssDNA. The catalytic activity of the ssDNA–RGO/cf-Pt nanocomposite for methanol oxidation was 2.5 fold of RGO/Pt and 3.8 fold of commercial Pt NPs. The outstanding catalytic activity of this novel catalyst was attributed to the very large surface of the highly conductive ssDNA–RGO and cotton-flower-like-Pt clusters with an open structure. The latter was beneficial for mass transfer. In addition, the excellent ability of the ssDNA–RGO/cf-Pt nanocomposite against CO poisoning was found and the anti-poisoning ratio (If/Ib) of ssDNA–RGO/cf-Pt was 1.75 fold larger than those of RGO/Pt and commercial Pt NPs. The elevated oxidation of CO in the adsorption state may be due to ssDNA providing abundant oxygen groups as well as the residual oxygen species in the RGO. A possible mechanism for the improved catalytic activity and CO tolerance was deduced according to UV-visible, Raman, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) results.

•Dandelion-like PtPd heterogeneous structure was fabricated by using HDPCl.•DPtPdNC with open structure provide abundant electrochemical active sites.•DPtPdNC show superior catalytic activity for ethanol oxidation and high stability.We successfully synthesized a dandelion-like PtPd heterogeneous structure via a facile one-pot hydrothermal route by reducing Na2PdCl4 and H2PtCl6 with ascorbic acid in the presence of hexadecylpyridinium chloride monohydrate. Hexadecylpyridinium chloride monohydrate acted as the shape-directing agent, which is critical to the reproducible formation of dandelion-like PtPd nanoclusters (DPtPdNC). The prepared DPtPdNC with an average diameter of 40 nm composed of dozens of branched arm assembled by Pt and Pd heterogeneous nanoseeds. DPtPdNC had a strong electron-electron interaction. What's more, there were numerous nanoscale steps, kinks and edges in DPtPdNC open channel structure. As a result, an optimized DPtPdNC made by fine-tuning ratio of the Pt (7%) and Pd (93%) showed hugely active surface sites and a superior electrocatalytic performance for ethanol oxidation was well as a long durability.

An intelligent PNIPAAm/AgNP composite film was fabricated by the simple assembly of silver nanoparticles on the surface of photo-polymerized PNIPAAm film via electrostatic interaction. Surface enhanced Raman scattering study and finite-difference time-domain simulation demonstrated that the local electric field intensity and the SERS intensity of this resultant composite film can be easily tuned by changing the interparticle distance triggered by temperature or solvent variations. The composite film showed a high stability in a polar organic solvent and concentrated saline solution. The smart composite film might find applications as a SERS sensor for temperature/solvent variation detection as well as a versatile SERS substrate for the detection of analyte in sea water and organic solvent.

Fabrication of cheap and disposable substrates with high surface enhanced Raman scattering (SERS) effects is essential for practical SERS application. In this study, versatile substrates (silica plate, polyethylene film and filter paper) were simply modified with polydopamine followed by in situ silver nanoparticle deposition to fabricate a two-dimensional SERS substrate. This kind of SERS substrate has good reproducibility (relative standard deviation (RSD) <8% (spot-to-spot) and <12% (batch-to-batch)) and stability (>89% after 2 months). Using 4-mercaptopyridine (4-Mpy) as the probe molecule, the enhancement factor could reach 107. This facile and general approach can be easily scaled up to fabricate cheap, easily portable, flexible and disposable SERS substrates, which can be applied for on-site SERS detection.

A simple acid-etching method was used to leach out silver from a bimetallic gold-silver based Digital Video Disc (DVD), which was further treated via a cyclic voltammetric scanning in 1 mmol/L HAuCl4 solution to create a porous gold nanostructure. The as-fabricated electrode was characterized by field-emission scanning electron microscopy, energy-dispersed X-ray spectroscopy and X-ray diffraction. The high electro-catalytic activity of the resulting electrode toward the reduction of hydrogen peroxide (H2O2) presented excellent linear relationship in the range of 8.0×10−5 to 1.26×10−2 mol/L with the detection limit of 2.0×10−5 mol/L (S/N=3). The as-developed non-enzyme-sensor showed good reproducibility, stability, and selectivity.

Surface enhanced Raman scattering (SERS) technique was used to observe the adsorption structure of serotonin (5-hydroxytryptamine, 5-HT) monolayers formed on silver electrode surface at pH 11 and also by the aid of density functional theory (DFT). The SERS spectrum implied that monolayers of 5-HT could be self-assembled on the silver surface through O10 and N6 atoms and the molecular plane should be tilted on the surface. In situ electrochemical SERS experiment was performed in 0.1 mol L−1 KCl solution to investigate the stability of the 5-HT monolayers on the silver electrode surface. It could be found that 5-HT monolayers on silver surface experienced the changes of adsorption fashions as the potential shifting to a more negative direction prior to complete detachment from the silver surface.Graphical abstractHighlights► Observation of the adsorption of 5-HT monolayers on the silver surface is conducted by SERS. ► Adsorption structure of 5-HT experienced a reorientation state with the applied potential. ► DFT method is used to elucidate the normal Raman and SERS data of 5-HT.

Surface enhanced Raman scattering (SERS) technique was used to observe the adsorption structure of serotonin (5-hydroxytryptamine, 5-HT) monolayers formed on silver electrode surface at pH 11 and also by the aid of density functional theory (DFT). The SERS spectrum implied that monolayers of 5-HT could be self-assembled on the silver surface through O10 and N6 atoms and the molecular plane should be tilted on the surface. In situ electrochemical SERS experiment was performed in 0.1 mol L−1 KCl solution to investigate the stability of the 5-HT monolayers on the silver electrode surface. It could be found that 5-HT monolayers on silver surface experienced the changes of adsorption fashions as the potential shifting to a more negative direction prior to complete detachment from the silver surface.Graphical abstractDownload full-size imageHighlights► Observation of the adsorption of 5-HT monolayers on the silver surface is conducted by SERS. ► Adsorption structure of 5-HT experienced a reorientation state with the applied potential. ► DFT method is used to elucidate the normal Raman and SERS data of 5-HT.

ssDNA was employed to readily disperse reduced graphene oxide (RGO) to form ssDNA–RGO composites, which could be used as a superior support to expediently electrodeposit Pt to synthesize ssDNA–RGO/cotton-flower-like-Pt nanocomposites (ssDNA–RGO/cf-Pt). The formation of cotton-flower-like-Pt clusters was due to the assistance of nitrogen atoms and phosphate groups in ssDNA. The catalytic activity of the ssDNA–RGO/cf-Pt nanocomposite for methanol oxidation was 2.5 fold of RGO/Pt and 3.8 fold of commercial Pt NPs. The outstanding catalytic activity of this novel catalyst was attributed to the very large surface of the highly conductive ssDNA–RGO and cotton-flower-like-Pt clusters with an open structure. The latter was beneficial for mass transfer. In addition, the excellent ability of the ssDNA–RGO/cf-Pt nanocomposite against CO poisoning was found and the anti-poisoning ratio (If/Ib) of ssDNA–RGO/cf-Pt was 1.75 fold larger than those of RGO/Pt and commercial Pt NPs. The elevated oxidation of CO in the adsorption state may be due to ssDNA providing abundant oxygen groups as well as the residual oxygen species in the RGO. A possible mechanism for the improved catalytic activity and CO tolerance was deduced according to UV-visible, Raman, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) results.