Photoinduced Charge Transfer Mechanism Research Articles

Revealing Photoinduced Charge Transfer Mechanism of SnO2/BiOBr S-Scheme Heterostructure for CO2 Photoreduction

Revealing Photoinduced Charge Transfer Mechanism of SnO2/BiOBr S-Scheme Heterostructure for CO2 Photoreduction

Exploring the mechanism of photoinduced charge transfer based on a dspirobifluorene- decorated donor under an external electric field

Exploring the mechanism of photoinduced charge transfer based on a dspirobifluorene- decorated donor under an external electric field

Preparation of 1D/1D perylene diimide nano-rod modified Bi4O7 rod with highly active photocatalytic performance

Preparation of 1D/1D perylene diimide nano-rod modified Bi4O7 rod with highly active photocatalytic performance

Photoelectrochemical activity of visible light-responsive BiVO4@La1-xSrxFeO3-δ (x = 0, 0.2, 0.4) heterojunction architectures – Optimizing activity by tuning Fe[sbnd]O bond in perovskites

Photoelectrochemical activity of visible light-responsive BiVO4@La1-xSrxFeO3-δ (x = 0, 0.2, 0.4) heterojunction architectures – Optimizing activity by tuning Fe[sbnd]O bond in perovskites

Photophyical and photosensitizing properties of BODIPYs substantially changed by alkyl- and phenyl-amino groups on meso carbon

meso-RNH (R=C3H7, C4H9, PhCH2, H, and Ph) substituted BODIPY compounds have been prepared to examine their photophysical properties and photosensitizing abilities. We have measured the UV-vis absorption, steady state and time resolved fluorescence, excited triplet state formation using laser flash photolysis, singlet oxygen generation ability using chemical trapping method. The results show that the presence of meso-RNH leads to large blue shift of absorption and emission wavelength, remarkable decrease in fluorescence quantum yield and lifetime values, and significant increase in singlet oxygen formation quantum yield. Quantum chemical calculation also reveals the photoinduced charge transfer (PCT) mechanism. We conclude that property changes are due to: 1) S0 and S1 geometry, 2) ground state structural isomerization, and 3) intramolecular PCT. These results and mechanisms are helpful for designing new functional materials.

Vis–NIR Electrochromism and NIR–Green Electroluminochromism in Dual Functional Benzothiadiazole‐Arylamine Mixed‐Valence Compounds

AbstractElectrochromism/electrofluorochromism is the reversible tuning of the absorption/photoluminescence by redox processes. Dual functional electrochromic/electrofluorochromic materials can be exploited in, for example, smart windows, encryption/anticounterfeiting technologies, displays, and biomedical sensors. While electrofluorochromic materials showing tunable fluorescence intensity are relatively widespread, those with tunable color emission are not. Moreover, electrofluorochromic materials with tunable emission in the near‐infrared (NIR) range are seldom encountered. Here, this work shows a new molecular approach to afford both the above functionalities, in addition to red–NIR electrochromism, by combining the properties of highly stable arylamine radical cation mixed valence species, with those of donor–acceptor systems exhibiting the photoinduced twisted intramolecular charge transfer mechanism.

New insight into the mechanism of symmetry-breaking charge separation induced high-valent iron(Ⅳ) for highly efficient photodegradation of organic pollutants

Fe 3+ mediating photodegradation of organic pollutants has attracted extensive attention in the field of environment remediation. However, most works focused on low concentration ( C Fe <1 mM) system under UV light, in which hydroxyl radicals (•OH) is the main radical for pollutants degradation. In this work, we discover a new mechanism of visible light induced (VLI) symmetry-breaking charge separation for pollutants degradation in high-concentration Fe 3+ system (HC-Fe 3+ , C Fe >1 mM). The formed binuclear hydrolyzed Fe 3+ species ([(H 2 O) 4 Fe(μ-OH) 2 Fe(H 2 O) 4 ] 4+ ) in HC-Fe 3+ system significantly broadens the optical absorption range and induces to the generation of Fe(Ⅳ), thus leading to highly efficient degradation of organic pollutants. In addition, a logarithmic correlation between the adiabatic ionization potential (AIP) and the reaction rate constant ( k ) of organics is obtained. The new findings further broaden the knowledge on the generation of Fe(Ⅳ) and the photo-induced charge transfer mechanism of binuclear hydrolyzed Fe 3+ species in the VLIHC-Fe 3+ system. ● Fe(Ⅳ) was generated in visible light induced high-concentration Fe 3+ system ● Photo-induced symmetry-breaking charge separation of Fe 3+ dimer was revealed ● Red-shift of absorption edge of Fe 3+ solution due to the generation of Fe 3+ dimer ● Structure-activity relationship for organic degradation in Fe 3+ system was found

Defect-Mediated Electron Transfer in Pt-CuInS2/CdS Heterostructured Nanocrystals for Enhanced Photocatalytic H2 Evolution

The effective separation of photogenerated electrons and holes is the key to improve photocatalytic activity in hydrogen evolution reaction (HER). However, the mechanism of photoinduced charge transfer between the cocatalyst and the semiconducting heterojunction in a single nanocrystal is vague at present. Herein, the relationships between the crafted cocatalyst and the constructed semiconducting heterojunction in a single nanocrystal were verified. Manipulating these relationships will improve the performance of visible light-driven hydrogen evolution. As a model, we used CuInS2 (CIS) nanocrystals (NCs) modified by the cocatalyst platinum (Pt) NCs and the semiconductor cadmium sulfide (CdS), forming the ternary heterostructured NCs (HNCs). Under visible light irradiation, the photocatalytic activity in hydrogen evolution of Pt-CIS/CdS HNCs is 6.38 and 1.76 times higher than those of pristine CIS NCs and CIS/CdS HNCs, respectively. Transient absorption measurements certified that the high photocatalytic activity in the HER was attributed to the photoinduced electron transfer from the defect-mediated trap state in CIS to the cocatalyst Pt, which was superior to the direct Z-scheme heterojunction between CIS and CdS. This research paves a route for the design of a suitable cocatalyst and the formation of heterostructured semiconducting NCs for boosting the photocatalytic activity in solar energy conversion.

Synthesis of Co3O4 nanospheres for enhanced photo-assisted supercapacitor

The design of the novel photo-assisted supercapacitor electrodes is considered an effective way to store abundant solar energy and improve energy storage performance. However, the mechanism of photo-induced charge transfer undergoing semiconductor energy band levels is still unclear. Herein, we have synthesized Co3O4 nanospheres (p-type semiconductor) for photo-assisted supercapacitors, and proposed its mechanism of enhanced photo-assisted energy storage by supported experiments and density functional theory (DFT) investigations. Results show the photo-generated charge produced by Co3O4 with semiconductor characteristics will promote the charging reaction under continuous light. After the charging process, the semiconductor characteristics gradually disappear, and the generated Co2+−OH is not sensitive to light response. On the basis of this result, we further propose a new type of light-assisted strategy in tandem with a n-type semiconductor (TiO2) additional electrode, which can provide photo-generated electrons and holes in the charge/discharge processes. The specific capacitance (523 F g−1) under light with TiO2 assisting is increased by 16.7% when compared with that without TiO2-assisted under dark (450 F g−1) at 1 A g−1. This work may provide a theoretical basis and new strategy for improving the energy storage capacity of supercapacitors.

Physical Insight into the Mechanism of Photoinduced Charge-Transfer and its Effects on Gas Mixture Adsorption in the Metal-Organic Framework: A Study Combining Quantum Mechanics Calculations and Molecular Mechanics Simulations

Physical Insight into the Mechanism of Photoinduced Charge-Transfer and its Effects on Gas Mixture Adsorption in the Metal-Organic Framework: A Study Combining Quantum Mechanics Calculations and Molecular Mechanics Simulations

Facile synthesis of Super-paramagnetic Au @α-Fe2O3 hybrid nanoparticle and its assembly on graphene substrate for visible light Photo-catalysis

• Facile and scalable chemical synthesis of Au@α-Fe2O3 nanostructure. • Interface modified strategy to self-assemble the as-synthesized Au@Fe2O3 nanostructures on graphene substrate. • Au@α-Fe2O3/graphene exhibited excellent photocatalytic activity under visible-light. • Amphoteric catalytic activity in degradation of cationic as well as anionic dyes. • The Au@α-Fe2O3/graphene catalyst exhibited a highly stability and recyclability. We report a simple interface modified strategy to self-assemble the as-synthesized Au@Fe 2 O 3 nano structures by facile chemical synthesis route on graphene substrate (AFG) fo r substrate mediated photo-catalytic dye degradation. The substrate modification, film formation, photo induced charge transfer mechanism and the physico-chemical properties of the AFG has been systematically analysed using different analytical techniques. The alteration in light absorption capacity and band gap of the hybrid with respect to the individuals have been observed using diffuse reflectance spectroscopy. Moreover, the broad absorption in the visible range and squeeze in band gap of the hybrid from 2.3 to 1.97 eV confirms the ability of the hybrid and the intention of hybridization for visible light-responsive photo-catalysis. Additionally, interesting superparamagnetic behaviour of the hybrid and its magnetic separation ability has been explored. Further, the applicability, repeatability and versatility of this AFG hybrid material in catalytic degradation of different dyes in presence of visible light have been analysed. This AFG catalyst exhibits excellent photocatalytic activity against the decolouration of the both cationic and anionic dyes. A systematic study in the photo-catalytic degradation behaviour, kinetic of degradation and the postulated mechanism has been proposed.

Amorphous Ni(OH)2 nanocages as efficient SERS substrates for selective recognition in mixtures

Surface-enhanced Raman scattering (SERS) technology has become one of the most powerful tools for identifying trace analytes due to its outstanding merit of fingerprint spectrum. It has been found that noble metal (Ag, Au) materials can produce obvious surface plasmon resonance under visible light illumination, which can bring out a strong SERS effect. However, due to poor stability and non-selectivity, its practical applications are seriously hindered, especially for the detection of polluted water contaminating mixture organic pollutants. Herein, we designed an amorphous Ni(OH) 2 nanocages (a-Ni(OH) 2 NCs) substrate that exhibits an excellent SERS performance with good spectral stability and selectivity, which is attributed to the strong interfacial photo-induced charge transfer (PICT) mechanism between a-Ni(OH) 2 NCs and molecules. Due to the effective vibrational coupling of a-Ni(OH) 2 NCs and molecule under laser irradiation, the PICT transitions between a-Ni(OH) 2 NCs and molecules evidently increase the molecular polarizability tensor and magnify molecular Raman scattering cross-section, resulting in a remarkable SERS activity. Besides, in wastewater containing several nitrogen and phosphorus pollutants, we successfully identified methylene blue and crystal violet molecules by using a-Ni(OH) 2 NCs due to their selective recognition function. This research points out a new application direction for SERS technology in water pollution detection based on non-metal substrates, which widely broadens application prospects of SERS spectroscopy. • High-SERS-performance amorphous Ni(OH) 2 nanocages were successfully synthesized. • a-Ni(OH) 2 NCs possess large specific surface area and optical resonance cavities. • Amorphous nanomaterials favor photo-induced charge transfer (PICT) mechanism. • a-Ni(OH) 2 SERS substrates possess selective recognition function in mixed wastewater.

Physical Mechanism of Photoinduced Charge Transfer in One- and Two-Photon Absorption in D-D-π-A Systems.

The photoinduced charge transfer process of a D-π-A molecule (W1) and three D-D-π-A molecules (WS5–WS7) with triphenylamine as a donor was studied theoretically. D-D-π-A molecules are formed by inserting donors between the triphenylamine and π-linker (π-bridge) on the base of the W1 molecule. The results showed that donor insertion resulted in a red shift in the absorption spectrum, and the absorption intensity increased to a certain extent. A visualization method was used to observe the charge transfer of the four molecules in the process of one- and two-photon absorption (TPA). The local excitation enhanced charge transfer excitation in the TPA process was analyzed and discussed, and the insertion of the thiazolo[5,4-d]thiazole donor showed the largest TPA cross-section. This work contributed to the profound understanding of D-D-π-A molecules and the design of large cross-section TPA molecules.

Tuning the Fluorescence and the Intramolecular Charge Transfer of Phenothiazine Dipolar and Quadrupolar Derivatives by Oxygen Functionalization.

A series of new naphthalimide and phenothiazine-based push–pull systems (NPI-PTZ1–5), in which we structurally modulate the oxidation state of the sulfur atom in the thiazine ring, i.e., S(II), S(IV), and S(VI), was designed and synthesized by the Pd-catalyzed Sonogashira cross-coupling reaction. The effect of the sulfur oxidation state on the spectral, photophysical, and electrochemical properties was investigated. The steady-state absorption and emission results show that oxygen functionalization greatly improves the optical (absorption coefficient and fluorescence efficiency) and nonlinear optical (hyperpolarizability) features. The cyclic voltammetry experiments and the quantum mechanical calculations suggest that phenothiazine is a stronger electron donor unit relative to phenothiazine-5-oxide and phenothiazine-5,5-dioxide, while the naphthalimide is a strong electron acceptor in all cases. The advanced ultrafast spectroscopic measurements, transient absorption, and broadband fluorescence up conversion give insight into the mechanism of photoinduced intramolecular charge transfer. A planar intramolecular charge transfer (PICT) and highly fluorescent excited state are populated for the oxygen-functionalized molecules NPI-PTZ2,3 and NPI-PTZ5; on the other hand, a twisted intramolecular charge transfer (TICT) state is produced upon photoexcitation of the oxygen-free derivatives NPI-PTZ1 and NPI-PTZ4, with the fluorescence being thus significantly quenched. These results prove oxygen functionalization as a new effective synthetic strategy to tailor the photophysics of phenothiazine-based organic materials for different optoelectronic applications. While oxygen-functionalized compounds are highly fluorescent and promising active materials for current-to-light conversion in organic light-emitting diode devices, oxygen-free systems show very efficient photoinduced ICT and may be employed for light-to-current conversion in organic photovoltaics.

Study of photo induced charge transfer mechanism of PEDOT with nitro groups of RDX, HMX and TNT explosives using anti-stokes and stokes Raman lines ratios

The paper reports the charge transfer mechanism between poly (3,4-ethylenedioxythiophene) (PEDOT) and high energy materials such as RDX, HMX and TNT, respectively in terms of ratios of anti-stokes (AS) and stokes(S) Raman lines of NO2 bands. Generally it works as an effective sensing medium for the detection of explosives when mixed in an equal proportion and are subjected to 532nm wavelength without any chemical treatment [1]. The pristine PEDOT is less sensitive to 532nm wavelength (2.33eV) but influences the Raman S and AS lines of explosives in the mixture. The study also reveals that a small quantity (one milligram) of PEDOT is sufficient to initiate the positive charge transfer mechanism between its oxidized state to the lone pairs of electrons on the oxygen atoms of the nitro group of the explosive molecules. Consequently, the intensity of the Raman spectra of RDX, HMX and TNT is dropped by an order of 22.5, 11.45 and 17.2 times, respectively along with the shift of the NO2 vibrational modes. It is also attributed to Photon-electron-phonon interaction. Finally, we have estimated the reduced mass of the functional group to ascertain the force constant and the intensity ratios of AS /S lines to confirm the charge transfer mechanism. The effect of charge transfer mechanism is also reflected in drastic change in transmission /absorption characteristics of FTIR spectra of same PEDOT and explosive mixtures.

Mechanism of photoinduced charge transfer at MEH-PPV and titanium dioxide nanoparticle interface

In this study, we investigated mechanisms of photoinduced electron transfer from a conjugated polymer (poly(2-methoxy-5-(2-ethylhexyloxy) 1,4-phenylenevinylene (MEH-PPV) to titanium dioxide (TiO 2 ) nanoparticles (acceptor) through steady-state photoluminescence (PL) spectroscopy. Since mixed phase TiO 2 has better photocatalytic compared to single phase, it is an efficient charge separation process during photoexcitation of polymer nanocomposites by incorporating the mixed phase TiO 2 nanoparticles into the MEH-PPV polymer matrix through in situ polymerization. Structural characterization revealed only physical interaction between the polymer matrix and dispersed nanoparticles. The absorbance spectra of nanocomposites also indicated the absence of ground state complex formation. Luminescence quenching of polymer nanocomposites compared to pristine MEH-PVV signifies the charge transfer taking place at the MEH-PPV/TiO 2 interfaces. Thus, the MEH-PPV/ mixed phase TiO 2 nanocomposite serves as an active layer for photovoltaic application.

WO3-x/Si n-n homotype heterojunction with high performance photodetection characteristics

Abstract WO3 has a great potential in the field of optoelectronics. Herein, sub-stoichiometric WO3-x thin film is prepared and WO3-x/Si n-n homotype heterojunction with pronounced rectifying behavior is constructed. Moreover, the heterojunction exhibits excellent photodetection characteristics, including a large responsivity of 72.8 A/W, a high specific detectivity of 3.96 × 1011 Jones and fast response times of 5.8 μs/1.27 ms. The mechanism of photoinduced charge separation and transfer in the WO3-x/Si n-n homotype heterojunction is analyzed by Kelivn probe force microscopy. These results suggest that the WO3-x/Si n-n homotype heterojunction is of excellent performance in the field of optoelectronic application.

Physical mechanism of special type photoinduced charge transfer in one-photon and two-photon absorption of Mobius rings.

In this work, the monomers and dimers of the Mobius ring were studied using density functional theory (DFT), symmetric matching perturbation theory (SAPT) and various excited state wave function analysis methods. The one-photon and two-photon absorption and their charge transfer excitation characteristics of the Mobius ring were qualitatively and quantitatively analyzed. The exchange-related induced super-exchange charge transfer, charge sequence transfer and local excitation-enhanced charge transfer were analyzed and discussed. The relationship between the super-exchange action and the transition distance and the degree of electron hole density separation is obtained. A mechanism to enhance charge transfer excitation was discovered during the two-photon transition.

Wo &lt;sub&gt;3-X&lt;/sub&gt;/Si N-N Homotype Heterojunction with High Performance Photodetection Characteristics

WO3 has a great potential in the field of optoelectronics. Herein, sub-stoichiometric WO3-x thin film is prepared and WO3-x/Si n-n homotype heterojunction with pronounced rectifying behavior is constructed. Moreover, the heterojunction exhibits excellent photodetection characteristics, including a large responsivity of 72.8 A/W, a high specific detectivity of 3.96 ×1011 Jones and fast response times of 5.8 μs/1.27 ms. The mechanism of photoinduced charge separation and transfer in the WO3-x/Si n-n homotype heterojunction is analyzed by Kelivn probe force microscopy. These results suggest that the WO3-x/Si n-n homotype heterojunction is of excellent performance in the field of optoelectronic application.

Physical Insight on Mechanism of Photoinduced Charge Transfer in Multipolar Photoactive Molecules

Two series of novel dyes were designed based on the multipolar structures of the red dye D35 and blue dye DB, by introducing the furan (F), benzene ring (B) and benzo[c]thiophene (BT) groups into the conjugated bridge of D35 in proper order and adjusting the position of diketopyrrolopyrrole(DPP) unit and the incorporation of fluorine in the conjugated bridge of DB, respectively. We performed the quantum chemistry calculation to investigate the ground state and excited properties in a direct correlation with the spectra properties and abilities of losing or accepting electron for the original and designed molecules. Furthermore, the absorption spectra characteristics in consideration of the aggregation of dyes on the TiO2 layer and intermolecular charge transfer rate of the dimers were calculated. The obtained results indicate that the larger intermolecular charge transfer rate leads to the poor photoelectrical properties of the dyes, and the designed dyes D35-3 and DB-2 would exhibit the best photoelectrical properties among the investigated dyes due to their lower energy gaps, widened absorption spectra and prominent charge transfer properties.