Academic literature on the topic 'Stimuli-responsive emission'

Recently, tunable photonic crystals (PhCs) have received great research interest, thanks to the wide range of applications in which they can be employed, such as light emission and sensing, among others. In addition, the versatility and ease of fabrication of PhCs allow for the integration of a large range of responsive elements that, in turn, can permit active tuning of PhC optical properties upon application of external stimuli, e.g., physical, chemical or even biological triggers. In this work, we summarize the most employed theoretical tools used for the design of optical properties of responsive PhCs and the most used fabrication techniques. Furthermore, we collect the most relevant results related to this field, with particular emphasis on electrochromic devices.

Poly(2-isopropyl-2-oxazoline) (POx), a typical thermo-responsive polymer, was conjugated with a tetraphenylethene derivative, having aggregation induced emission behavior, towards the thermal control of their fluorescence emission.

Crystallization of a luminogen normally red-shifts and weakens its emission. During investigation of some luminogens exhibiting aggregation-induced emission (AIE), we first noticed that some AIE active luminogens display higher photoluminescence (PL) intensity and bluer emission in the crystalline state than in their amorphous phase, which is termed as crystallization induced emission enhancement (CIEE). The twisted conformations of CIEE active molecules afford loose packing patterns and rule out any detrimental strong interaction. Molecular conformations are locked more tightly in crystals than those in amorphous solid due to the regular weak interactions in crystals, which affords the CIEE effect. The loose packing patterns facilitate emission switching through morphology modulation. Many AIE active molecules have been developed based on restriction of intramolecular rotation (RIR) mechanism, and we obtained many CIEE compounds from those AIE active luminogens and investigated their utilities as stimuli responsive functional materials, especially as chemosensors, thermosensor, mechanosensors and solid-state emitters. Thus, we provide a possible design strategy for the stimuli responsive solid luminescent materials.

A new cyano-distyrylbenzene derivative with mechano-induced high contrast change in color and emission was demonstrated. Under mechanical stimuli, the emission peak can redshift from 440 nm to 650 nm, while the appearance can switch from white to pink.

The main thrust of this thesis is the development of facile synthetic routes for simple boryl anilines and study their structure-property correlations in both solid and solution states and to utilize this information to design functional materials with desired properties such as aggregation induced emission, mechanofluorochromism, and thiol sensors. This thesis contains eight chapters and the contents of each chapter are described below. Chapter 1 The first chapter is an introduction to the theme of the thesis and presents a general review on the present work with emphasis on photophysics of triarylboron based donor-acceptor systems and their applications in various fields. In addition, advances in boron chemistry in the new frontier areas such as aggregation induced emission and mechanochromism are discussed in brief. Chapter 2 The second chapter deals with the general experimental techniques and synthetic procedures utilized in this work. Chapter 3 This chapter describes the rational design and synthesis of triarylborane bearing Unsubstituted amines, namely borylanilines (3.1-3.5). Compounds 3.1-3.4have similar donor and acceptor centres but differ their molecular conformations and also differ in the relative positions of amine moiety (para and meta). Compounds 3.1-3.4 contain one amine group while 3.5 contains two amine moieties. These compounds exhibit fascinating electrostatic intermolecular interactions, N −H- - -π in the crystal structure of 3.1, 3.2 and 3.4 and N −H--N interactions in crystal structure of 3.5. The solution state optical properties of 3.1-3.5 are typical of donor-acceptor (D-A) systems. Interestingly, compounds 3.3 and 3.5 showed unprecedented mechanochromic luminescent properties. Upon grinding, compound 3.3 showed color changes from blue to cyan blue and 3.5 showed intriguing color changes from blue to green and these color changes were found to be reversible. Single crystal X-ray diffraction analysis of 3.5BP (blue emission color crystal) and 3.5GP (green emission color crystal) clearly show that the color changes are due to the difference in their solid state packing. Chapter 4 In chapter 4, the design and facile synthesis of boron based donor-acceptor (D-A) systems such as borylanilines 4.4-4.9 (D= -NH2 for 4.4-4.6 and -NMe2 for compounds 4.7-4.9) are reported. Compounds 4.4, 4.5 and 4.6 contain one, two or three -NH2 moiety(ies), respectively. Compounds 4.7, 4.8 and 4.9 contain one, two or three –NMe2 moiety(ies), respectively. A systematic investigation has been carried out to rationalize the effect of donor-acceptor ratio on the ICT process in borylanilines 4.4-4.9. The aryl spacer between donor amine and acceptor boron is kept the same in all the compounds to avoid the electronic effect of spacer on the ICT characteristics of these compounds. In the case of compounds 4.4-4.6, the increase in the number of donor -NH2 moieties does not affect their absorption profile, while in the case of compounds 4.7-4.9, the absorption spectra are shifted bathochromically with an increase in the number of donor-NMe2 moieties. Photoluminescence (PL) of 4.4-4.6 is significantly blue shifted with an increase in number of –NH2 moieties, while the PL of 4.7-4.9 was slightly blue shifted. The absorption and PL features of 4.4-4.6 are sensitive to the polarity of the solvent medium. In contrast, absorption profiles of 4.7-4.9 are not sensitive to the polarity of the solvent medium. The PL of these compounds is affected by the polarity of the solvent medium. Chapter 5 This chapter deals with triarylboron based fluorescent probes (5.1-5.4) for the selective detection of thiophenols over aliphatic thiols. The probes were constructed by conjugating luminescent borylanilinies with luminescent quencher 2,4-dinitrobenzene sulfonyl (DNBS) moiety. In compound 5.1 and 5.2 the DNBS moiety is positioned at the para position with respect to the triarylborane moiety, while in 5.3 and 5.4 the DNBS moiety(ies) is(are) at the meta position(s). Probes 5.1-5.4 showed selective turn-on fluorescence response towards thiophenol. The fluorescence “off-on” switching mechanism of 5.1-5.4 against thiophenols was fully elucidated by theoretical calculations. Probes 5.1-5.4 are also capable of detecting thiophenols in the intra cellular environments. Chapter 6 Design, facile synthesis and aggregation induced emission properties of a new series of novel triarylboron tethered N-aryl-1,8-naphthalimides (TAB-NPIs) 6.1-6.7 are described in this chapter. Systematic structural perturbation has been used for fine-tuning the optical and morphological properties of TAB- NPIs in both solid as well as in aggregated state. Compounds 6.1-6.7 are weekly luminescent in solutions. In contrast, all compounds (except compound 6.4) are strongly luminescent in the solid state and aggregated state in THF-H2O mixtures. The presence of sterically hindered boryl unit in 6.1-6.7 has endowed these molecules with unique AIE characteristics by preventing co-facial arrangements of NPI moieties. The propeller shape arrangement of TAB moiety in 6.1, 6.2, 6.5, 6.6 and 6.7 effectively prevents the aggregation induced emission quenching (AIEQ) and induce strong emission in the condensed state. In the solid state, compounds 6.1, 6.4, 6.5, and 6.6 generate an interesting supramolecular structure via intermolecular C-H--- and C-H---O interactions. No face to face intermolecular π---π interactions were found in the crystal structures of 6.1, 6.4, 6.5, and 6.6. This precludes the excimer formation which can be detrimental to the radiative process in these molecules. The scanning electron microscopy (SEM) images of as prepared samples of 6.1-6.7 clearly indicate that the morphology of these compounds strongly depends on the molecular conformations and number of naphthalimide moieties in the TAB-NPI conjugates. Chapter 7 This chapter deals with design, synthesis and optical properties of novel dimesitylboryl appended perylenediimides. A simple synthetic strategy has been developed for the construction of novel TAB-PDIs conjugates. These conjugates can be conveniently synthesised by condensation of boryl anilines with perylene tetracarboxylic acid anhydride. The incorporation of TAB moiety enhanced the solubility of perylen bisimides in common organic solvents. The PL quantum yield of both 7.1 and 7.2 strongly depends on the excitation wavelength. Lower Pl efficiency observed for 7.1 and 7.2 upon excitation in the boryl dominated absorption region may be due to the photon induced electron transfer form mesityl units of boryl to perylene bisimide moiety. The morphology as well as emission colours of supramolecular architectures of both 7.1 and 7.2 can be modulated by controlling the concentrations of DCM solutions of these compounds. Both the compounds showed selective fluorogenic response for F-1 and CN-1 anions. The simple synthetic strategy reported in this chapter can be conveniently exploited for the construction of TAB conjugates of semiconducting organic anhydrides. Chapter 8 Novel planar chiral Lewis acids 8.3(SP, SS), 1-phosphino-2-borylferrocenes 8.4(SP) and 2-phosphino-1-borylferrocenes 8.4(RP) have been synthesized from a readily accessible ferrocene sulphinate precursor. Adopting a simple synthetic approach and a single precursor, enantiomerically pure SP and RP isomers have been prepared. It would be worthwhile to investigate the catalytic properties of compounds 8.3(SS), 8.4(SP) and 8.4(RP). It would also be interesting to replace the mesityl groups on boron with other electron deficient groups like pentafluorophenyl and 1,3,5-trifluoromethylphenyl to fine tune the Lewis acidity of boron center and to set-up a general route to enantiomerically pure Planar Chiral Frustrated Lewis Pairs (PCFLP’s).

博士
國立交通大學
材料科學與工程學系所
105
The pivotal objective of this dissertation is to design and construct novel fluorescent switchable mechanically interlocked molecular architectures with symmetric stopper and to study their molecular shuttling process under acid-base stimuli control along with their controllable high contrast fluorescence and impressively selective detection of anionic guest species. In the introduction of this doctoral thesis we have described brief early synthetic attempts to create mechanically interlocked molecules (MIMs) such as rotaxanes and catenanes as well as several chemosensing mechanism and aggregation induced emission (AIE). Moreover novel templating methodologies to build MIMs and some latest examples of fluorescence MIMs based molecular shuttles under different control stimuli were also introduced. Indeed, acid-based stimuli can drive the molecular shuttling between the two stations accompanied by changing the AIE behavior of AIE-active mechanically interlocked molecule investigated. Fairly, underplayed chemo sensing mechanisms in these systems were presented. Meanwhile, we have developed facile ratiometric sequential detection of copper and pyrophosphate based on rhodamine appended derivatives in this doctoral thesis as well. In chapter two, a novel multifunctional mechanically interlocked switchable [2]rotaxane R4 containing two molecular stations and rotaxane arms terminated with boron-dipyrromethene (BODIPY) fluorophores and its derivatives were synthesized for the first time by CuAAC click reaction. The shuttling motion of macrocycle between the dibenzylammonium and triazolium recognition sites and the distance dependent photoinduced electron transfer process of R4 is demonstrated by utilizing external chemical stimuli (acid/base). Interestingly, the reversible self-assembly process of R4 was recognized by the acid–base molecular switch strategy. Notably, two symmetrical triazolium groups acted as molecular stations, H2PO4– receptors, and H-bonded donors. Both [2]rotaxane R4 and thread R2 demonstrated excellent optical responses and high selectivity toward H2PO4– ion. The specific motion and guest–host interactions of mechanically interlocked machines (MIMs) were also further explored by quantum mechanical calculations. The thread R2 also demonstrated to enable the detection of H2PO4– in RAW 264.7 cells successfully. In chapter three, a novel near IR fluorescent switchable [2]rotaxane NIR4 composed of two different molecular stations and rotaxane arms terminated with near IR boron-dipyrromethene (BODIPY) fluorophores and its derivatives were synthesized for the first time by CuAAC click chemistry. The molecular shuttling motion could be addressed by the fluorescence signal transduction via distance dependent photo-induced electron transfer process of [2]rotaxane NIR4 triggered by external chemical stimuli (acid/base). The construction and efficient synthesis of [2]rotaxane NIR4 with high level of structural complexity designed always more challenging task of selective anion sensing. Conspicuously, the key to design involved encoding the flexible arms of [2]rotaxane NIR4 triazolium moiety acted as molecular stations and H-bonded donors, which exhibits impressive selectivity and sensitivity toward complementary anionic gust species. The specific mechanical molecular motion of [2]rotaxane NIR4, host-guest interactions of NIR2 and mechanically interlocked molecules (MIMs) were also further explored by quantum mechanical calculations. Importantly, the host of NIR2 and [2]rotaxane NIR4 could be applied for the vivo imaging and clarify the distribution of H2PO4- at subcellular levels. In chapter four, a novel AIE-active switchable [2]rotaxane TR2 incorporating two different molecular stations and rotaxane arms terminated with AIE-active TPE fluorophores and its derivatives were synthesized for the first time by click chemistry. The shuttling behavior of macrocycle component between the two molecular stations can be driven by external acid-base stimuli in solution, accompanied by NMR spectral changes. Investigation of their AIE fluorescence behavior changes showed that these analogous rotaxane are controlled by the molecular motion of the macrocycle component in the presence of external acid-base stimuli. The anion-templated construction of [2]rotaxane TR2 with high level of structural complexity designed always more challenging task. Evidently, the key to design involved encoding the flexible arms of both triazolium motif, is described which exhibit impressive selectivity and sensitivity toward complementary anionic gust species. The specific mechanical molecular motion and host-guest interactions of mechanically interlocked machines (MIMs) were also further explored by quantum mechanical calculations. Importantly, the AIE- active behaviors of [2]rotaxanes TR1, TR2 and TR3 were further investigated to study their potential bio-imaging application and specifically [2]rotaxane TR2 could be applied in vivo imaging with H2PO4- at subcellular levels. In chapter five, two rhodamine hydrazine derivatives Rh1 and Rh2 with catechol and ether functionalities have been synthesized and utilized towards sequential colorimetric detections of Cu(II) and pyrophosphate (PPi) ions in CH3CN–H2O (v/v = 9 : 1, 5 mM Tris–HCl, pH 7.4) semi-aqueous medium. Notably, Rh1 and Rh2 are the first example of colorimetric rhodamine-based probes for the sequential detections of Cu2+ ion and PPi anion. Based on the significant colorimetric responses (from colorless to pink) of Rh1 and Rh2 to Cu2+ ions, the detection limits were estimated as low as 1.22 × 10−8 M and 8.0 × 10−7 M, respectively, which signified the utilities of designed probes towards facile detections of Cu2+ ions. Furthermore, upon the successive addition of PPi ion to Rh1–Cu2+ and Rh2–Cu2+complexes, it has been altered and restored to its origin of Rh1 and Rh2 via re-coordination of PPi to Cu2+ ion, which was confirmed by color changes from pink to colorless. Moreover, computational DFT calculations provided more insights into HOMO–LUMO structures of rhodamine derivatives and their copper complexes. Additionally, the solid state strip-based colorimetric detections of Cu2+ ion were supplemented as a real time application. Thus in conclusion, novel fluorescence mechanically interlocked molecules designed to act as molecular switches have proceeded apace. Delightfully, the molecular shuttling to achieve by the addition of acid-base and studied on AIE behavior indicate that the molecular motion of macrocycle component could induce change the aggregation state of the AIE-active mechanically interlocked molecule. The remarkable stimulated responses towards dihydrogen phosphate (H2PO4-) were discussed. Furthermore, sequential detection of copper and pyrophosphate via ratiometric sensor based on rhodamine derivatives were presented in detail.

Abstract The integration of additive manufacturing technologies with stimuli-responsive shape memory materials allows the dynamic self-adaptation of fabricated parts upon exposure to external stimulations. The additional dimension of time inspires the concept of four-dimensional printing technology. However, the emerging feedstock materials and the employment of external stimuli in 4D printing are also associated with new workplace hazards and occupational health concerns. Current evaluation studies on additive manufacturing are mainly focused on the safety and health effects that originated from the part production phase and cannot be directly applied in 4D printing processes. In this study, the emissions of volatile organic compounds from stereolithography-based 4D printing process with thermo-responsive materials are targeted as the potential safety concern. Real-time total volatile organic compound monitoring is conducted during various production phases to align the emission sources with critical operating activities, including both operator interventions and machine operations. Comparative experiments are performed to evaluate the effectiveness of proposed emission control strategies. In particular, alterations in operation procedures such as stirring speed in material mixing and post-printing stimulation method can contribute positively to air emission control during manual operations. In addition, the installation of activated carbon fiber filters inside the machine build chamber can lead to a significant reduction of air emissions during part fabrication with an overall total volatile organic compound concentration reduction of 58.91%.