scholarly journals Interfacial Charge Transfer Processes in 2D and 3D Semiconducting Hybrid Perovskites: Azobenzene as Photoswitchable Ligand

2019 ◽  
Author(s):  
Nicole Fillafer ◽  
Tobias Seewald ◽  
Lukas Schmidt-Mende ◽  
Sebastian Polarz
Keyword(s):  
Energy Transfer ◽  
Perovskite Phase ◽  
Molecular Switches ◽  
Head Group ◽  
Stimuli Responsive ◽  
Pi Conjugated ◽  
Hybrid Perovskite ◽  
Pi System ◽  
2D And 3D ◽  
Interfacial Charge

<p>In the vast majority of studies on semiconductor particles one uses ligands, respectively capping agents, which bind to the external surfaces of the particles and cover it with an electrically insulating shell. Since transport of charge carrier and/ or energy across interfaces is desirable for a large number of applications, the use of pi-conjugated ligands becomes more and more interesting. Among those, compounds which show stimuli-responsive properties, particularly molecular switches are fascinating, as one hopes to be able to adjust the properties of the interfaces by demand. However, how the properties of such special ligands get influenced by the presence of a semiconductor and vice-versa is under debate. Here, ammonium-modified azobenzene compounds were selected as prototypes for molecular switches and organic-inorganic hybrid perovskites on the semiconductor side. The class of ammonium-lead-halide phases as prototypes is special, because in addition to surface functionalization of 3D crystals, organic compounds can be truly incorporated into the crystal as 2D phases yielding, for example, layered Ruddelsden-Popper phases. We present photoswitchable azobenzene ligands with varying head group lengths for the synthesis of 2D and 3D hybrid perovskite phases. Energy transfer mechanisms are influenced by the length of the molecular spacer moiety, which determines the distance between the pi-system to the semiconductor surfaces. We find huge differences in the photoswitching behaviour between the free, surface coordinated versus ligands integrated inside perovskite layers. Photoswitching of azobenzene ligands incorporated to 2D phases is nearly quenched, while the same mechanism for coordinating ligands is greatly improved, compared to the free ligands. The improvement originates from an energy transfer from the perovskite to the azobenzene, which is strongly distance dependent. This study provides evidence for the photoswitching behaviour of azobenzene as ligand for hybrid perovskites and the dependence of the head group between a chromophore and the perovskite phase.</p>

scholarly journals Interfacial Charge Transfer Processes in 2D and 3D Semiconducting Hybrid Perovskites: Azobenzene as Photoswitchable Ligand

2019 ◽  
Author(s):  
Nicole Fillafer ◽  
Tobias Seewald ◽  
Lukas Schmidt-Mende ◽  
Sebastian Polarz
Keyword(s):  
Energy Transfer ◽  
Perovskite Phase ◽  
Molecular Switches ◽  
Head Group ◽  
Stimuli Responsive ◽  
Pi Conjugated ◽  
Hybrid Perovskite ◽  
Pi System ◽  
2D And 3D ◽  
Interfacial Charge

<p>In the vast majority of studies on semiconductor particles one uses ligands, respectively capping agents, which bind to the external surfaces of the particles and cover it with an electrically insulating shell. Since transport of charge carrier and/ or energy across interfaces is desirable for a large number of applications, the use of pi-conjugated ligands becomes more and more interesting. Among those, compounds which show stimuli-responsive properties, particularly molecular switches are fascinating, as one hopes to be able to adjust the properties of the interfaces by demand. However, how the properties of such special ligands get influenced by the presence of a semiconductor and vice-versa is under debate. Here, ammonium-modified azobenzene compounds were selected as prototypes for molecular switches and organic-inorganic hybrid perovskites on the semiconductor side. The class of ammonium-lead-halide phases as prototypes is special, because in addition to surface functionalization of 3D crystals, organic compounds can be truly incorporated into the crystal as 2D phases yielding, for example, layered Ruddelsden-Popper phases. We present photoswitchable azobenzene ligands with varying head group lengths for the synthesis of 2D and 3D hybrid perovskite phases. Energy transfer mechanisms are influenced by the length of the molecular spacer moiety, which determines the distance between the pi-system to the semiconductor surfaces. We find huge differences in the photoswitching behaviour between the free, surface coordinated versus ligands integrated inside perovskite layers. Photoswitching of azobenzene ligands incorporated to 2D phases is nearly quenched, while the same mechanism for coordinating ligands is greatly improved, compared to the free ligands. The improvement originates from an energy transfer from the perovskite to the azobenzene, which is strongly distance dependent. This study provides evidence for the photoswitching behaviour of azobenzene as ligand for hybrid perovskites and the dependence of the head group between a chromophore and the perovskite phase.</p>

scholarly journals Interfacial charge transfer processes in 2D and 3D semiconducting hybrid perovskites: azobenzene as photoswitchable ligand

2020 ◽  
Vol 11 ◽  
pp. 466-479
Author(s):  
Nicole Fillafer ◽  
Tobias Seewald ◽  
Lukas Schmidt-Mende ◽  
Sebastian Polarz
Keyword(s):  
Energy Transfer ◽  
Perovskite Phase ◽  
Molecular Switches ◽  
Head Group ◽  
Hybrid Perovskite ◽  
External Stimuli ◽  
2D And 3D ◽  
Interfacial Charge ◽  
Transfer Mechanisms ◽  
Lead Halide

In the vast majority of studies on semiconductor particles ligands or capping agents are used that bind to the surface of the particles covering them with an electrically insulating shell. Since the transport of charge carriers and/or energy across interfaces is desirable for a variety of applications, the use of π-conjugated ligands becomes increasingly interesting. Among them are compounds that react to external stimuli. Molecular switches in particular are fascinating because the properties of the interfaces can be potentially adjusted as required. However, there is debate about how the properties of such special ligands are influenced by the presence of a semiconductor and vice versa. Here ammonium-modified azobenzene compounds were selected as prototypes for molecular switches and organic–inorganic hybrid perovskites as semiconductor materials. The class of ammonium–lead–halide phases as prototypes is peculiar because, in addition to the surface functionalization of 3D crystals, organic compounds can actually be incorporated into the crystal as 2D phases. Thus, for example, layered Ruddlesden–Popper phases are obtained. We present photoswitchable azobenzene ligands with different head-group lengths for the synthesis of 2D and 3D hybrid perovskite phases. The energy transfer mechanisms are influenced by the length of the molecular spacer moiety, which determines the distance between the π system and the semiconductor surfaces. We find huge differences in the photoswitching behaviour between the free, surface-coordinated and integrated ligands between the perovskite layers. Photoswitching of azobenzene ligands incorporated in 2D phases is nearly quenched, while the same mechanism for surface-coordinating ligands is greatly improved, compared to the free ligands. The improvement originates from an energy transfer from perovskite to azobenzene, which is strongly distance-dependent. This study provides evidence for the photoswitching of azobenzenes as ligands of hybrid perovskites, which depends on the spacing between the chromophore and the perovskite phase.

scholarly journals Redox-triggered switching in three-dimensional covalent organic frameworks

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Chao Gao ◽  
Jian Li ◽  
Sheng Yin ◽  
Junliang Sun ◽  
Cheng Wang
Keyword(s):  
Solid State ◽  
Three Dimensional ◽  
Molecular Switches ◽  
Pore Channel ◽  
Pore Surface ◽  
Stimuli Responsive ◽  
Conversion Yield ◽  
Responsive Materials ◽  
Reversible Transformation ◽  
Internal Pore

Abstract The tuning of molecular switches in solid state toward stimuli-responsive materials has attracted more and more attention in recent years. Herein, we report a switchable three-dimensional covalent organic framework (3D COF), which can undergo a reversible transformation through a hydroquinone/quinone redox reaction while retaining the crystallinity and porosity. Our results clearly show that the switching process gradually happened through the COF framework, with an almost quantitative conversion yield. In addition, the redox-triggered transformation will form different functional groups on the pore surface and modify the shape of pore channel, which can result in tunable gas separation property. This study strongly demonstrates 3D COFs can provide robust platforms for efficient tuning of molecular switches in solid state. More importantly, switching of these moieties in 3D COFs can remarkably modify the internal pore environment, which will thus enable the resulting materials with interesting stimuli-responsive properties.

Synthesis and self-assembly of photoacid-containing block copolymers based on 1-naphthol

2019 ◽  
Vol 10 (41) ◽  
pp. 5602-5616 ◽  
Author(s):  
Felix Wendler ◽  
Jessica C. Tom ◽  
Felix H. Schacher
Keyword(s):  
Block Copolymers ◽  
Self Assembly ◽  
Molecular Switches ◽  
Amphiphilic Block Copolymers ◽  
Strong Increase ◽  
Stimuli Responsive ◽  
Responsive Materials

Photoacids experience a strong increase in acidity when absorbing light and, hence, can be considered as molecular switches. The incorporation into amphiphilic block copolymers leads to novel stimuli-responsive materials with great potential.

scholarly journals Hybrid Al2O3-CH3NH3PbI3 Perovskites towards Avoiding Toxic Solvents

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 243 ◽  
Author(s):  
Eurig Wyn Jones ◽  
Peter James Holliman ◽  
Leon Bowen ◽  
Arthur Connell ◽  
Christopher Kershaw ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Perovskite Phase ◽  
Three Dimensions ◽  
Thermal Mass ◽  
X Ray Diffraction ◽  
Hybrid Perovskite ◽  
Processed Material ◽  
Organic Capping ◽  
Perovskite Nanoparticles ◽  
Capping Ligands

We report the synthesis of organometal halide perovskites by milling CH3NH3I and PbI2 directly with an Al2O3 scaffold to create hybrid Al2O3-CH3NH3PbI3 perovskites, without the use of organic capping ligands that otherwise limit the growth of the material in the three dimensions. Not only does this improve the ambient stability of perovskites in air (100 min versus 5 min for dimethylformamide (DMF)-processed material), the method also uses much fewer toxic solvents (terpineol versus dimethylformamide). This has been achieved by solid-state reaction of the perovskite precursors to produce larger perovskite nanoparticles. The resulting hybrid perovskite–alumina particles effectively improve the hydrophobicity of the perovskite phase whilst the increased thermal mass of the Al2O3 increases the thermal stability of the organic cation. Raman data show the incorporation of Al2O3 shifts the perovskite spectrum, suggesting the formation of a hybrid 3D mesoporous stack. Laser-induced current mapping (LBIC) and superoxide generation measurements, coupled to thermogravimetric analysis, show that these hybrid perovskites demonstrate slightly improved oxygen and thermal stability, whilst ultra-fast X-ray diffraction studies using synchrotron radiation show substantial (20×) increase in humidity stability. Overall, these data show considerably improved ambient stability of the hybrid perovskites compared to the solution-processed material.

CHARGE AND ENERGY TRANSFER IN BINAPHTHALENE MOLECULE WITH TWO SPIROPYRAN UNITS USED FOR CHIRAL MOLECULAR SWITCHES AND LOGIC GATES

2006 ◽  
Vol 05 (02) ◽  
pp. 163-174 ◽  
Author(s):  
MENGTAO SUN ◽  
FENGCAI MA
Keyword(s):  
Energy Transfer ◽  
Charge Transfer ◽  
Absorption Spectra ◽  
Transition Density ◽  
Logic Gates ◽  
Molecular Switches ◽  
Transition Dipole Moment ◽  
Real Space ◽  
Transition Dipole ◽  
Contour Plots

A new binaphthalene molecule with two spiropyran units used for chiral molecular switches and logic gates was synthesized and characterized.12 In this paper, charge and energy transfer in binaphthalene molecule with two spiropyran units are theoretically investigated with quantum chemistry method, as well as 2D and 3D real space analysis methods, since molecule construction with photoinduced electron transfer or charge transfer is one of the most frequently used pathways for building useful sensors and molecular machines. The orientation and strength of transition dipole moment in absorption spectra are obtained by 3D transition density. The orientation and results of intramolecular charge transfer on the excitation are obtained with 3D charge difference densities. The electron-hole coherence and excitation delocalization in absorption spectra are investigated with 2D contour plots of transition density matrix. Overall, the computed results remain in good agreement with the relevant experimental data, and the theoretical results reveal the relationship between the function of sensor and the excited state properties of the structure and transformation of the compound, upon addition of acid and base in absorption spectra.

Solvatochromic, thermochromic and pH-sensory DCDHF-hydrazone molecular switch: response to alkaline analytes

RSC Advances ◽  
2016 ◽  
Vol 6 (104) ◽  
pp. 102296-102305 ◽  
Author(s):  
Tawfik A. Khattab ◽  
Brylee David B. Tiu ◽  
Sonya Adas ◽  
Scott D. Bunge ◽  
Rigoberto C. Advincula
Keyword(s):  
Molecular Switches ◽  
Molecular Switch ◽  
Stimuli Responsive

Nanostructures fabricated from multi-stimuli responsive DCDHF-hydrazone molecular switches to function as colorimetric reversible gas probes.

scholarly journals Temperature-Responsive Molecular Assemblies Using Oligo(Ethylene Glycol)-Attached Polyamidoamine Dendron Lipids and their Functions as Drug Carriers

2020 ◽  
Vol 11 (1) ◽  
pp. 16
Author(s):  
Takuya Hashimoto ◽  
Yuji Hirai ◽  
Eiji Yuba ◽  
Atsushi Harada ◽  
Kenji Kono
Keyword(s):  
Ethylene Glycol ◽  
Drug Carrier ◽  
Drug Carriers ◽  
Head Group ◽  
Stimuli Responsive ◽  
Alkyl Chains ◽  
Temperature Responsive ◽  
Poly Ethylene ◽  
External Stimuli

Temperature-responsive nanocarrier systems using external stimuli are one of the most widely investigated stimuli-responsive strategies because heat is easy and safe to use for hyperthermia and controlled drug delivery. Polyamidoamine dendron lipids (PAMAM-DLs) composed of PAMAM dendron as head group and two alkyl chains can exhibit temperature-responsive morphological change through the attachment of suitable moieties to terminal of PAMAM dendron. In this study, oligo(ethylene glycol)s including ethoxy- or methoxy-diethylene glycols were attached to the terminals of PAMAM-DL, and temperature-responsive properties of their self-assemblies were evaluated by calorimetric and turbidity measurements. In the evaluation of temperature-responsive properties, ethoxy diethylene glycol (EDEG)-attached PAMAM-DL composed of two saturated alkyl chains and PAMAM dendron with 1st generation had lipid bilayer structure and suitable cloud point for the application as drug carrier. In vitro performances of the assemblies combining EDEG-attached PAMAM-DLs with cholesteryl-oxy-poly(ethylene glycol) (PEG-Chol) was evaluated using doxorubicin (DOX) as an anticancer drug. Cellular uptake of DOX-loaded EDEG-attached PAMAM-DL/PEG-Chol assemblies was promoted at 42 °C rather than 37 °C, resulting in an effective decrease in cell viability.

Imidazole and triazole head group-containing polydiacetylenes for colorimetric monitoring of pH and detecting HCl gas

2018 ◽  
Vol 2 (2) ◽  
pp. 291-295 ◽  
Author(s):  
Woolin Lee ◽  
Dayoung Lee ◽  
Ji-Yeong Kim ◽  
Songyi Lee ◽  
Juyoung Yoon
Keyword(s):  
Conjugated Polymers ◽  
Head Group ◽  
Stimuli Responsive ◽  
The Family ◽  
Hcl Gas

The family of conjugated polymers known as polydiacetylenes (PDAs) has been extensively utilized in designing stimuli-responsive colorimetric and fluorometric sensors.

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