Jinsheng Zhao

Preparation of sulfonic-functionalized graphene oxide as ion-exchange material and its application into electrochemiluminescence analysis

Graphene oxide (GO) obtained from chemical oxidation of flake graphite was derivatized with sulfonic groups to form sulfonic-functionalized GO (GO-SO(3)(-)) through four sulfonation routes: through amide formation between the carboxylic group of GO and amine of sulfanilic acid (AA-GO-SO(3)(-)), aryl diazonium reaction of sulfanilic acid (AD-GO-SO(3)(-)), amide formation between the carboxylic group of GO and amine of cysteamine and oxidation by H(2)O(2) (CA-GO-SO(3)(-)), and alkyl diazonium reaction of cysteamine and oxidation by H(2)O(2) (CD-GO-SO(3)(-)). Results of Fourier transform infrared spectroscopy and X-ray photoelectrospectrocopy showed that -SO(3)(-) groups were attached onto GO. Thermo gravimetric analysis showed that derivatization with sulfonic groups improved thermo stability of GO. X-ray diffraction results indicated that GO-SO(3)(-) had more ordered π-π stacking structure than the original GO. GO-SO(3)(-) and cationic polyelectrote, poly (diallyldimethylammoniumchloride) (PDDA) were adsorbed at indium tin oxide (ITO) glass surface through layer-by-layer assembling to form (GO-SO(3)(-)/PDDA)(n)/ITO multilayers. After tris-(2,2-bipyridyl) ruthenium (II) dichloride (Ru(bpy)(3)(2+)) was incorporated into the multilayers, the obtained Ru(bpy)(3)(2+)/(GO-SO(3)(-)/PDDA)(n)/ITO electrodes can be used as electrochemiluminescence sensors for detection of organic amine with high sensitivity (limit of detection of 1 nM) and stability.

Ethylene glycol stabilized NaBH4 reduction for preparation carbon-supported Pt–Co alloy nanoparticles used as oxygen reduction electrocatalysts for microbial fuel cells

Three carbon-supported Pt–Co alloys with varying Pt to Co atom ratio (Pt2–Co/C, Pt–Co/C, Pt–Co2/C) were prepared by NaBH4 reduction in ethylene glycol at room temperature. As supported by X-ray diffraction, all the prepared Pt–Co nanoparticles have a single-phase face-centered cubic structure. Transmission electron microscopy indicates that all nanoparticles have small particle-size range and are highly dispersed on carbon support. Catalytic properties of the synthesized Pt–Co alloy catalysts were analyzed using cyclic voltammetry and linear sweep voltammetry methods, and the results suggested that Pt–Co/C catalysts exhibit the best Pt mass activity and the highest stability for the oxygen reduction reaction (ORR) when compared with Pt/C catalyst and other Pt–Co alloy catalyst in both acidic and neutral media. Kinetic analysis reveals that the ORR on Pt–Co alloy follows the four-electron pathway leading to water. As the cathode catalyst, the single-chamber microbial fuel cell tests indicated the much better performance of Pt–Co alloy than that of commercial Pt/C.

Controlled synthesis of Pt nanoparticles array through electroreduction of cisplatin bound at nucleobases terminated surface and application into H2O2 sensing.

Fabrication of sub-monolayer array of Pt nanoparticles (PtNPs) assembled at nucleobases terminated layers and their application into H(2)O(2) and glucose sensing were reported. To prepare such a PtNPs assembly, 3-mercaptopropionic acid (MPA), Zr(4+), nucleotide-5-monophosphate (NTMP including guanosine, adenosine, cytidine, uridine-5-monophosphate, and abbreviations were GMP, AMP, CMP, UMP, respectively) were adsorbed onto Au substrate sequentially to form nucleobases terminated surface and Zr(4+) acted as binder to link carboxylic and phosphoric groups (NTMP/Zr(4+)/MPA/Au). Complexation of cisplatin, cis-Pt(NH(3))(2)Cl(2), with terminated nucleobases and following electrochemical reduction of surface-bound cisplatin gave PtNPs attached surface. Different PtNPs coverage or particle density was obtained depending on the NTMP used and decreased in the order: PtNPs/GMP/Zr(4+)/MPA/Au>PtNPs/AMP/Zr(4+)/MPA/Au>PtNPs/CMP/Zr(4+)/MPA/Au>PtNPs/UMP/Zr(4+)/MPA/Au. The surface loading of Pt was between 160 and 16 ng/cm(2). The as prepared PtNPs can be used as electrocatalysts for H(2)O(2) sensing (detection limit of H(2)O(2)<100 nM) and the sensitivity increased with decreasing PtNPs density. After adsorption of glucose oxidase, the modified electrode can be used as enzymatic electrode for glucose sensing and a detection limit of 38.5 μM was achieved. This study provided an example of fabricating PtNP arrays utilising surface complexation of cisplatin with nucleobases. The advantage of this method is that the NP density can be controlled through changing nucleobases or Pt complexes used to obtain suitable kinetics of the complexation reactions. Additionally, the PtNPs sub-monolayer as prepared has high sensitivity for H(2)O(2) sensing even at a very low loading of Pt.

Donor–acceptor type polymers containing the 2,3-bis(2-pyridyl)-5,8-dibromoquinoxaline acceptor and different thiophene donors: electrochemical, spectroelectrochemistry and electrochromic properties

Three donor–acceptor type π-conjugated polymers, poly[2,3-di(2-pyridyl)-5,8-bis(2-thienyl)quinoxaline] (PPTQ), poly[2,3-di(2-pyridyl)-5,8-bis(2-(3-butylthiophen))quinoxaline] (PPBTQ) and poly[2,3-di(2-pyridyl)-5,8-bis(2-(3,4-ethylenedioxythiophene))quinoxaline] (PETQ), containing the 2,3-di(2-pyridyl) quinoxaline moiety in the backbone as the acceptor unit and different thiophene derivatives as donor units were synthesized electrochemically. Characterization of the corresponding polymers was conducted by cyclic voltammetry (CV), UV-vis-NIR spectroscopy and scanning electron microscopy (SEM). Spectroelectrochemistry and electrochemical analyses demonstrated that all three polymers can undergo both p- and n-type doping processes. PPTQ exhibits purple red color in the reduced state, violet blue color in the neutral state, and gray blue color in the oxidation state. PPBTQ exhibits red color in the reduced state, light steel blue color in the neutral state, and dark slate blue color in the oxidation state. PPETQ exhibits green color in the reduced state, yellow color in the neutral state, and a colorless highly transmissive state in the oxidation state. PPETQ and PPBTQ revealed excellent optical contrasts of 80.3% and 78.2%, respectively, in the NIR region. The outstanding optical contrasts in the NIR region, high stability and fast switching times make these polymers excellent candidates for NIR device applications.

Layered and Pb-Free Organic–Inorganic Perovskite Materials for Ultraviolet Photoresponse: (010)-Oriented (CH3NH3)2MnCl4 Thin Film

Organic-inorganic lead perovskite materials show impressive performance in photovoltaics, photodetectors, light-emitting diodes, lasers, sensors, medical imaging devices, and other applications. Although organic-inorganic lead perovskites have shown good performance in numerous fields, they contain toxic Pb, which is expected to cause environmental pollution in future large-scale applications. Thus, the photoelectric properties of Pb-free organic-inorganic perovskite materials should be developed and studied. In this paper, we report on the photoresponse of Pb-free organic-inorganic hybrid manganese perovskite (CH3NH3)2MnCl4. To the best of our knowledge, this study demonstrates the first time that organic-inorganic hybrid manganese perovskites are used for this type of application. We found that the solution-processed MA2MnCl4 thin film tends to be oriented along the b-axis direction on the TiO2 surface. The evident photoresponse of the FTO/TiO2/MA2MnCl4/carbon electrode devices was observed under 10-30 Hz flashlight frequencies and a 330 nm light beam. This simple, green, and low-cost photoresponsive device is beneficial for the future industrial production of optical recorders and optical memory devices.

Two novel ambipolar donor–acceptor type electrochromic polymers with the realization of RGB (red-green-blue) display in one polymer

Two novel electrochromic monomers, 4,7-bis(4-methoxythiophen-2-yl)-[1,2,5]thiadiazolo[3,4-c]pyridine (MOTTP) and 4,7-bis(4-butoxythiophen-2-yl)-[1,2,5]thiadiazolo[3,4-c]pyridine (BOTTP), were synthesized and electropolymerized to give the corresponding polymers PMOTTP and PBOTTP, respectively. For the investigation of their electrochemical and electrochromic properties, the polymers were characterized using cyclic voltammetry (CV), UV-vis spectroscopy, step profiling, and scanning electron microscopy (SEM). The band gaps of the polymers were calculated based on spectroelectrochemical analysis, and were found to be 0.950 eV and 1.088 eV for PMOTTP and PBOTTP, respectively. Electrochromic investigations showed that PMOTTP and PBOTTP showed similar multichromic behaviors: saturated green color in the neutral state, highly transmissive blue in the oxidized state, and saturated red in the reduced state (red-green-blue, RGB). In addition, both polymers have excellent switching properties with more than 60% optical contrast in the NIR region and about a 0.5 s response time from neutral to oxide. Moreover, via electrochemical and spectral analyses both polymers were proven to be n-type dopable polymers. Hence, both polymers are promising materials to complete RGB electrochromic polymers for commercial applications.

The optimization of donor-to-acceptor feed ratios with the aim of obtaining black-to-transmissive switching polymers based on isoindigo as the electron-deficient moiety

Isoindigo (iI)-containing donor (D)–acceptor (A)-type polymers have rarely been used as electrochromic materials although their applications in the field of organic photoelectric devices have achieved significant progress in only a few years. Three conjugated polymers, namely, P1–P3, were synthesized via the random copolymerization of three units, including thiophene and 3,3-bis-decyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (ProDOT-decyl2) as the D units, and alkyl-substituted isoindigo as the A unit, and the reactions were conducted by the Stille polymerization method. The results showed that the feed ratio of the D units to the A unit had a substantial effect on the electrochemical properties, optical band gap, color presentation, and electrochromic parameters (changes in transmittance, response time, coloration efficiency and persistence of optical contrasts for a long period) of the conjugated polymers. Polymers were easily obtained with the feed ratios (thiophene:iI:ProDOT) of 2:1:1, 4:1:3, and 5:1:4 for P1, P2 and P3, respectively. P1 exhibits a cyan color in the neutral state and a transmissive grey color in the oxidized state. Both P2 and P3 display a change from black to transmissive on conversion from the neutral to the oxidized state. An increase in the ProDOT content was helpful for enabling the extension of the absorption peak of the polymers across the entire spectrum and also improving the switching property of the polymers. In general, the introduction of iI as the A unit for the construction of D–A-type polymers provides the field of electrochromic devices with verifiable performance and deserves further investigation to obtain more promising electrochromic materials.

From two-dimensional graphene oxide to three-dimensional honeycomb-like Ni3S2@graphene oxide composite: insight into structure and electrocatalytic properties

Three-dimensional (3D) graphene composites have drawn increasing attention in energy storage/conversion applications due to their unique structures and properties. Herein, we synthesized 3D honeycomb-like Ni3S2@graphene oxide composite (3D honeycomb-like Ni3S2@GO) by a one-pot hydrothermal method. We found that positive charges of Ni2+ and negative charges of NO3− in Ni(NO3)2 induced a transformation of graphene oxide with smooth surface into graphene oxide with wrinkled surface (w-GO). The w-GO in the mixing solution of Ni(NO3)2/thioacetamide/H2O evolved into 3D honeycomb-like Ni3S2@GO in solvothermal process. The GO effectively inhibited the aggregation of Ni3S2 nanoparticles. Photoelectrochemical cells based on 3D Ni3S2@GO synthesized at 60u2009mMu2009l−1 Ni(NO3)2 exhibited the best energy conversion efficiency. 3D Ni3S2@GO had smaller charge transfer resistance and larger exchange current density than pure Ni3S2 for iodine reduction reaction. The cyclic stability of 3D honeycomb-like Ni3S2@GO was good in the iodine electrolyte. Results are of great interest for fundamental research and practical applications of 3D GO and its composites in solar water-splitting, artificial photoelectrochemical cells, electrocatalysts and Li-S or Na-S batteries.

Low Band Gap Donor–Acceptor Type Polymers Containing 2,3-Bis(4-(decyloxy)phenyl)pyrido[4,3-b]pyrazine as Acceptor and Different Thiophene Derivatives as Donors

Four donor–acceptor type conducting polymers, namely poly(2,3-bis(4-decyloxy)phenyl)-5,8-bis(4-thiophen-2-yl)pyrido[4,3-b]pyrazine) (P1), poly(2,3-bis(4-decyloxy)phenyl)-5,8-bis(4-butylthiophen-2-yl)pyrido[4,3-b]pyrazine) (P2), poly(2,3-bis(4-(decyloxy)phenyl)-5,8-bis(4-hexyloxythiophen-2-yl)pyrido[4,3-b]pyrazine) (P3) and poly(2,3-bis(4-(decyloxy)phenyl)-5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)pyrido[4,3-b]pyrazine) (P4), containing thiophene or its derivative as the donor and pyrido[4,3-b]pyrazine as the acceptor were prepared and characterized by cyclic voltammetry, scanning electron microscopy, and UV-Vis spectroscopy to detect the influence of the donor units’ strength on the electrochromic performances. The results demonstrated that all of the polymers could be reversibly reduced and oxidized by p-type doping and n-type doping, and showed near-infrared activities and different color changes in p-type doping process. Especially, P3 and P4 showed lower optical band gap than P1 and P2 due to the strong electron-donating hexyloxythiophen group of P3 and ethylenedioxythiophene group of P4. Besides, P3 and P4 displayed the saturated green color at the neutral state and the desirable transparency at the oxidized state. All the polymers displayed desirable optical contrasts, satisfactory coloration efficiency, excellent stability and short switching time, which made the polymers fascinating candidates in the electrochromic device applications.

Effects of the acceptor pattern and substitution position on the properties of N-phenyl-carbazolyl based donor–acceptor–donor molecules

Four optoelectronic compounds based on the same donor (N-phenylcarbazole) and different acceptors of benzothiadiazole or benzoselenadiazole were designed and synthesized to investigate the effects of the substitution position and effects of the acceptor heteroatom on the properties of N-phenyl-carbazolyl based organic optoelectronic compounds. The results demonstrated that these four compounds have band gaps (2.25 to 2.59 eV) that are lower than that of carbazole (3.20 eV). For the acceptor moiety, the replacement of benzothiadiazole with benzoselenadiazole was beneficial for the polarization of the D–A compound. Different acceptors substituted at the 3-position of N-phenylcarbazole led to molecules with a higher degree of planar conjugation than molecules derived from acceptors substituted at the 2-position. The increase in polarity and conjugation degree of the D–A compounds gave rise to lower band gaps and redshifts in the UV-vis absorption spectra and fluorescence emission spectra compared to the corresponding compounds. Solvatochromism effects were observed for these four compounds in different polar solvents, accompanied by redshifts in the fluorescence emission spectra, which ranged from 509 nm to 596 nm. Using thermogravimetric analysis, the decomposition temperatures of all four materials were found to be above 400 °C.