Fabrication of an anionic polythiophene/layered double hydroxide ultrathin film showing red luminescence and reversible pH photoresponse

Abstract

Luminescent ordered ultrathin films (UTFs) based on a sulfonated polythiophene (SPT) and Mg-Al-layered double hydroxide (LDH) nanosheets have been fabricated by the layer-by-layer assembly method. UV-visible absorption and fluorescence spectroscopy showed that there was a stepwise and regular growth of the films with increasing number of deposition cycles. XRD, AFM, and SEM showed that the films had a periodic layered structure with a period of ca. 3.0 nm, and that the thickness can be finely controlled within the range ca. 26-100 nm. The SPT/LDH UTFs show well-defined polarized photoemission with an anisotropy of ca. 0.3, and they show a reversible luminescence response to changes in pH. Periodic density functional theoretical calculations gave a band energy of 1.85 eV for the SPT/LDH system and showed that the valence electrons of SPT can be confined in the energy wells formed by the LDH monolayers, which effectively inhibits both the nonradiative relaxation and the p-p stacking interaction of the polymer chromophores. V

Reflection-mode micro-spherical fiber-optic probes for in vitro real-time and single-cell level pH sensing

“…Ultra-thin layer sol-gel can be directly dip-coated onto the end face of either as-synthesized or surface modified optical fiber probes. Sub-micron thickness pH sensing films have been developed on platforms like microfluidic device [33–35] as well as fiber-optics based pH sensor [36–38]. However, most of the reported devices were operated in relatively large scale (hundred micrometers to centimeter level), and cannot provide sufficient detection sensitivity, pH resolution, and/or real-time monitoring ability.…”

Recent Advances in Stimuli‐Responsive Photofunctional Materials Based on Accommodation of Chromophore into Layered Double Hydroxide Nanogallery

“…LDHs with a stable interlayer structure have highly enhanced the optical/thermal stability and environmental compatibility of the interlayer chromophore molecules and can be used as a new host matrix in more potential applications. Yan et al [51] have fabricated a luminescent ordered UTF based on a anionic polythiophene (APT) and Mg-Al-LDH nanosheets by the LBL assembly method. The dependence of the maximum emission wavelength ( max ) on the pH value is divided into three main zones: the max decreases sharply from 591 to 578 nm as the pH value is decreased from 14 to 12; it decreases very slightly from 578 to 574 nm when the pH value decreases from 12 to 8; finally, when the pH value is decreased from 8 to 4, the max undergoes a decrease from 574 to 562 nm, which shows a nearly linear relationship with the pH.…”

Layered Double Hydroxide Materials: Assembly and Photofunctionality

“…The red-emissive (SPT/LDH) 32 UTF described above exhibited reversible responses toward pH in alternative dipping in aqueous at pH ¼ 4 and pH ¼ 13 [79].…”

“…Yan et al [77] have introduced LDH nanosheet as building block to combine different chromophores; in this case, materials with a rigid and ordered microenvironment, finely tuning emission color, and polarized multicolor luminescence can be achieved. Figure 42 shows the assembly process of multicolor emission materials employing APPP (blue) [76], APPV (orange) [78], SPT (red) [79], and BNMA (green) [95] as primary chromophores. The combination of these individual chromophores can obtain organic/inorganic UTFs with emission color throughout the whole visible region, even the white color emission.…”

“…Yan et al have presented a potential solution to these problems by assembling the polymers with rigid LDH nanosheets which can serve as a new inorganic/organic quantum well structure. Several anionic polymers, such as the derivates of poly (p-phenylene) [76], poly(phenylenevinylene) [78], and polythiophene [79], have been studied, and investigation on a sulfonated poly(p-phenylene) anionic derivate (APPP) will be particularly introduced below. …”