11 research outputs found
Porphyrin Nanocrystal Synthesized via Chemical Reaction Route: pH-Sensitive Reversible Transformation between Nanocrystals and Bulk Single Crystal
Crystalline
nanostructures with octahedral morphology have been
prepared by self-assembling of cationic porphyrin (H<sub>6</sub>TPyP)<sup>4+</sup>·4Cl<sup>–</sup> produced through chemical reaction
route in aqueous solution
depending on the synergistic interactions among hydrogen-bonding,
π–π
stacking, and ion pairing. Unexpectedly, the gradual decrease in
pH by the slow evaporation of solvent in the nano-octahedron aqueous
suspension obtained in situ led to the selective etching of the original
nanocrystal and the isolation of (H<sub>6</sub>TPyP)<sup>4+</sup>·4Cl<sup>–</sup> bulk single crystals in the last stage. More interestingly,
the increase in pH by adding water again into this bulk single-crystal-containing
system led to the regeneration of nano-octahedrons, indicating the
reversible transformation between porphyrin nano-octahedrons and bulk
single crystals triggered by pH. Mechanistic investigations through
powder and single-crystal X-ray diffraction analyses together with
the electron microscopic, in particular, HRTEM, clearly reveal that
the unique surface effect and anisotropic character of the nanomaterials
differing from the bulk organic materials are responsible for such
pH-sensitive reversible transformation of the two crystalline materials
by controlling the dissolution or aggregation of (H<sub>6</sub>TPyP)<sup>4+</sup>·4Cl<sup>–</sup>, which actually induces the
reversible formation and breaking
of the (pyridine)N<sup>+</sup>–H···Cl<sup>–</sup>···H–O(H<sub>2</sub>O)···H–N<sup>+</sup>(pyridine) hydrogen bonds among cationic porphyrin building
blocks at different pH. This result, to control the crystallinity
and the unprecedented reversible transformation between nanocrystal
and bulk single crystals just by tuning the pH of the synthesis process,
as well as the use of the peculiar nanoeffect such as surface effect
to adjust the self-assembling process, provides
useful a tool for the controllable synthesis of crystalline materials
and is expected to be helpful for further research and application
of organic nanomaterials
Porphyrin Nanocrystal Synthesized via Chemical Reaction Route: pH-Sensitive Reversible Transformation between Nanocrystals and Bulk Single Crystal
Crystalline
nanostructures with octahedral morphology have been
prepared by self-assembling of cationic porphyrin (H<sub>6</sub>TPyP)<sup>4+</sup>·4Cl<sup>–</sup> produced through chemical reaction
route in aqueous solution
depending on the synergistic interactions among hydrogen-bonding,
π–π
stacking, and ion pairing. Unexpectedly, the gradual decrease in
pH by the slow evaporation of solvent in the nano-octahedron aqueous
suspension obtained in situ led to the selective etching of the original
nanocrystal and the isolation of (H<sub>6</sub>TPyP)<sup>4+</sup>·4Cl<sup>–</sup> bulk single crystals in the last stage. More interestingly,
the increase in pH by adding water again into this bulk single-crystal-containing
system led to the regeneration of nano-octahedrons, indicating the
reversible transformation between porphyrin nano-octahedrons and bulk
single crystals triggered by pH. Mechanistic investigations through
powder and single-crystal X-ray diffraction analyses together with
the electron microscopic, in particular, HRTEM, clearly reveal that
the unique surface effect and anisotropic character of the nanomaterials
differing from the bulk organic materials are responsible for such
pH-sensitive reversible transformation of the two crystalline materials
by controlling the dissolution or aggregation of (H<sub>6</sub>TPyP)<sup>4+</sup>·4Cl<sup>–</sup>, which actually induces the
reversible formation and breaking
of the (pyridine)N<sup>+</sup>–H···Cl<sup>–</sup>···H–O(H<sub>2</sub>O)···H–N<sup>+</sup>(pyridine) hydrogen bonds among cationic porphyrin building
blocks at different pH. This result, to control the crystallinity
and the unprecedented reversible transformation between nanocrystal
and bulk single crystals just by tuning the pH of the synthesis process,
as well as the use of the peculiar nanoeffect such as surface effect
to adjust the self-assembling process, provides
useful a tool for the controllable synthesis of crystalline materials
and is expected to be helpful for further research and application
of organic nanomaterials
(Pc)Eu(Pc)Eu[<i>trans</i>-T(COOCH<sub>3</sub>)<sub>2</sub>PP]/GO Hybrid Film-Based Nonenzymatic H<sub>2</sub>O<sub>2</sub> Electrochemical Sensor with Excellent Performance
A facile
approach was developed for preparing the multilayer hybrid films of
mixed (phthalocyaninato) (porphyrinato) europium(III) triple-decker
compound (Pc)Eu(Pc)Eu[<i>trans</i>-T(COOCH<sub>3</sub>)<sub>2</sub>PP] (<b>1</b>) and graphene oxide (GO) using the solution-processing
QLS method. The combination of the nature of relatively high conductivity
and great surface area for GO with the electroactive and semiconductive
triple-decker compound in ITO electrode renders the hybrid film excellent
sensing property for H<sub>2</sub>O<sub>2</sub>, due to the optimized
triple-decker molecular packing in the uniform-sized nanoparticles
(ca. 70 nm) formed on the GO surface. The amperometric responses are
linearly proportional to the concentration of H<sub>2</sub>O<sub>2</sub> in the range of 0.05–1800 μM with a fast response time
of 0.03 s μM<sup>–1</sup>, a low detection limit of 0.017
μM, and good sensitivity of 7.4 μA mM<sup>–1</sup>. The present work represents the best result of tetrapyrrole-based
nonenzymatic electrochemical sensor for H<sub>2</sub>O<sub>2</sub>. Nevertheless, the triple-decker/GO/ITO also shows excellent stability,
reproducibility, and selectivity, indicating the great potential of
electroactive tetrapyrrole rare earth sandwich compounds in combination
with GO in the field of nonenzymatic electrochemical sensors
(TFPP)Eu[Pc(OPh)<sub>8</sub>]Eu[Pc(OPh)<sub>8</sub>]/CuPc Two-Component Bilayer Heterojunction-Based Organic Transistors with High Ambipolar Performance
Organic thin film transistor (OTFT)
devices fabricated by the solution-based QLS technique from a mixed
(phthalocyaninato)(porphyrinato) europium complex (TFPP)Eu[Pc(OPh)<sub>8</sub>]Eu[Pc(OPh)<sub>8</sub>] exhibit air-stable ambipolar performance
with mobilities of 6.0 × 10<sup>–5</sup> cm<sup>2</sup> V<sup>−1</sup> s<sup>−</sup>1 for holes and 1.4 ×
10<sup>–4</sup> cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> for electrons, respectively. In good contrast, the
two-component bilayer heterojunction thin film devices constructed
by directly growing (TFPP)Eu[Pc(OPh)<sub>8</sub>]Eu[Pc(OPh)<sub>8</sub>] on vacuum deposited (VCD) CuPc film using solution based QLS method
were revealed to show unprecedented ambipolar performance with carrier
mobilities of 0.16 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> for holes and 0.30 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> for electrons. In addition to the intrinsic role of p-type organic
semiconductor, the VCD CuPc film on the substrate also acts as a good
template that induces significant improvement over the molecular ordering
of triple-decker compound in the film. In particular, it results in
the change in the aggregation mode of (TFPP)Eu[Pc(OPh)<sub>8</sub>]Eu[Pc(OPh)<sub>8</sub>] from J-type in the single-layer film to
H-type in the bilayer film according to the UV–vis, XRD, and
AFM observations
Amphiphilic (Phthalocyaninato) (Porphyrinato) Europium Triple-Decker Nanoribbons with Air-Stable Ambipolar OFET Performance
An amphiphilic mixed (phthalocyaninato)
(porphyrinato) europium(III)
triple-decker complex [Pc(OPh)<sub>8</sub>]Eu[Pc(OPh)<sub>8</sub>]Eu[TP(CCCOOH)PP]
(<b>1</b>) with potential ambipolar semiconducting HOMO and
LUMO energy levels has been designed, synthesized, and characterized.
The OFET devices fabricated by quasi-Langmuir-Shäfer (QLS)
technique at the air/water interface with nanoparticle morphology
display hole mobility of 7.0 × 10<sup>–7</sup> cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> and electron
mobility of 7.5 × 10<sup>–7</sup> cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>, which reflects its ambipolar
semiconducting nature. However, the performance of the devices fabricated
via a “phase-transfer” method from <i>n</i>-hexane with one-dimensional nanoribbon morphology was significantly
improved by 3–6 orders of magnitude in terms of hole and electron
mobilities, 0.11 and 4 × 10<sup>–4</sup> cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>, due to the enhanced
π–π interaction in the direction perpendicular
to the tetrapyrrole rings associated with the formation of a dimeric
supramolecular structure building block depending on the intermolecular
hydrogen bonding between the neighboring triple-decker molecules in
the one-dimensional nanoribbons
Hierarchically Structured Porous Nitrogen-Doped Carbon for Highly Selective CO<sub>2</sub> Capture
Nitrogen-doping has proven to be
an effective strategy for enhancing
the CO<sub>2</sub> adsorption capacity of carbon-based adsorbents.
However, it remains challenging to achieve a high doping level of
nitrogen (N) and a significant porosity in a carbon material simultaneously.
Here we report a facile method that enables the fabrication of ordered
macroporous nitrogen-doped carbon with the content of N as high as
31.06 wt %. Specifically, we used poly(EGDMA-<i>co</i>-MAA)
microspheres as a template to fabricate the structure which can strongly
interact with melamine (the precursor of nitrogen-doped carbon framework),
self-assemble into three-dimensionally ordered structure, and be easily
removed afterward. Upon chemical activation, significant microporosity
is generated in this material without degrading its ordered macroporous
structure, giving rise to a hierarchically structured porous nitrogen-doped
carbon in which a remarkable N content (14.45 wt %) is retained. This
material exhibits a moderate CO<sub>2</sub> adsorption capacity (2.69
mmol g<sup>–1</sup> at 25 °C and 3.82 mmol g<sup>–1</sup> at 0 °C under 1 bar) and an extraordinarily high CO<sub>2</sub>/N<sub>2</sub> selectivity (134), which is determined from the single-component
adsorption isotherms based on the ideal adsorption solution theory
(IAST) method. This value far exceeds the CO<sub>2</sub>/N<sub>2</sub> selectivity of thus-far reported carbon-based adsorbents including
various nitrogen-doped ones. We believe that such an unprecedented
CO<sub>2</sub>/N<sub>2</sub> selectivity is largely associated with
the unusually high N content as well as the partially graphitic framework
of this material
Controlled Synthesis of Carbon Nanofibers Anchored with Zn<sub><i>x</i></sub>Co<sub>3–<i>x</i></sub>O<sub>4</sub> Nanocubes as Binder-Free Anode Materials for Lithium-Ion Batteries
The
direct growth of complex ternary metal oxides on three-dimensional
conductive substrates is highly desirable for improving the electrochemical
performance of lithium-ion batteries (LIBs). We herein report a facile
and scalable strategy for the preparation of carbon nanofibers (CNFs)
anchored with Zn<sub><i>x</i></sub>Co<sub>3–<i>x</i></sub>O<sub>4</sub> (ZCO) nanocubes, involving a hydrothermal
process and thermal treatment. Moreover, the size of the ZCO nanocubes
was adjusted by the quantity of urea used in the hydrothermal process.
Serving as a binder-free anode material for LIBs, the ZnCo<sub>2</sub>O<sub>4</sub>/CNFs composite prepared using 1.0 mmol of urea (ZCO/CNFs-10)
exhibited excellent electrochemical performance with high reversible
capacity, excellent cycling stability, and good rate capability. More
specifically, a high reversible capacity of ∼600 mAh g<sup>–1</sup> was obtained at a current density of 0.5 C following
300 charge–discharge cycles. The excellent electrochemical
performance could be associated with the controllable size of the
ZCO nanocubes and synergistic effects between ZCO and the CNFs
Surface Modification of Methylamine Lead Halide Perovskite with Aliphatic Amine Hydroiodide
By spin-coating method,
a thin layer of dodecylamine hydroiodide
(DAHI) is introduced to the surface of perovskite CH<sub>3</sub>NH<sub>3</sub>PbI<i><sub>x</sub></i>Cl<sub>3–<i>x</i></sub>. This layer of DAHI successfully changes the surface of perovskite
from hydrophilic to hydrophobic as revealed by the water contact angle
measurement. Significantly enhanced fluorescence intensity and prolonged
fluorescence lifetime are found for these modified films in comparison
to those of unmodified perovskite films, suggesting that the number
of structure defects is reduced dramatically. The compatibility between
the perovskite and hole transfer layer (HTL) is also improved, which
leads to more efficient hole collection from the perovskite layer
by HTL as revealed by the fluorescence spectra, fluorescence decay
dynamics, as well as the transient photocurrent measurements. Moreover,
the perovskite solar cells (PSCs) fabricated from these modified perovskite
films exhibit significantly improved humidity stability as well as
promoted photoelectron conversion efficiency (PCE). The result of
this research reveals for the first time that the layer of aliphatic
amino hydroiodide is a multiple functions layer, which can not only
improve the humidity stability but also promote the performance of
PSCs by reducing the defect number and improve the compatibility between
perovskite and HTL. Because the structure of aliphatic amines can
be functionalized with myriad of other groups, this perovskite modification
method should be very promising in promoting the performance of PSCs
Employing Singlet Fission into Boosting the Generation of Singlet Oxygen and Superoxide Radicals for Photooxidation Reactions
Developing highly efficient heavy-metal-free photosensitizers
(PSs)
for the production of reactive oxygen species (ROS) is urgent to achieve
wide applications of ROS, yet it remains a great challenge. As a proof
of concept, singlet fission (SF), possessing the exciton multiplication
ability with a maximum 200% triplet yield, is employed to generate
ROS. Herein, a metal-free tetracene dimer with a high yield (∼164%)
of long-lived triplets (>300 μs) is prepared and used to
generate
singlet oxygen (1O2) and superoxide radicals
(O2·–). Remarkably, 1O2 and O2·– yields are
boosted compared to the existing traditional PSs based on intersystem
crossing (ISC). The 1O2 yield reaches an unprecedented
∼148%, representing the highest value ever reported so far.
Thus, this SF PS shows an improved photooxidation activity over ISC
PSs. Additionally, the 1O2 and O2·– generation mechanisms are described clearly
by combining TA spectra and controlled experiments. This represents
the first example of utilizing the two triplet states produced by
SF to generate ROS and catalyze related reactions. The work not only
presents a strategy for generating and enhancing the 1O2/O2·– yield but also opens
up a new field for the application of SF
Exploring Hardness and the Distorted sp<sup>2</sup> Hybridization of B–B Bonds in WB<sub>3</sub>
In
this work, tungsten triboride (WB<sub>3</sub>) was successfully
synthesized at high pressure and high temperature. The structure was
reconfirmed to be WB<sub>3</sub> (<i>P</i>6<sub>3</sub><i>mmc</i>), and some part has a tungsten atomic defect according
to the measurement results of X-ray diffraction, high-resolution transmission
electron microscopy, and Rietveld refinement. The asymptotic Vickers
hardness that had eliminated influence of excess boron is 25.5 GPa
for WB<sub>3</sub>. This value is in good agreement with the previous
theoretic results. Proof of novel electron transfer between the tungsten
atom and the boron atom was found. A deficient amount of transfer
electron induces distorted sp<sup>2</sup> hybridization of B–B
bonds in WB<sub>3</sub>. The weakly directional sp<sup>2</sup> hybridization
of B–B bonds is an essential factor that can influence the
hardness of WB<sub>3</sub>. Our results are helpful to design new
hard and superhard materials of transition metal borides