Flexible surface-enhanced Raman scattering (SERS) sensors have attracted great attention as a portable and low-cost device for chemical and bio-detection. However, flexible SERS sensors tend to suffer low signal spatial homogeneity due to the uneven distribution of active plasmonic nanostructures (hot spots) and quick degradation of their sensitivity due to low adhesion of hot spots and flexible substrates during fast sampling. Herein, a large-area (20 × 20 cm 2 ) polyimide (PI)-based SERS sensor is exploited for trace detection with high signal homogeneity and stability. The SERS sensor is constructed from PI through in situ growth of silver and gold core−shell nanoparticles (Ag@Au NPs) based on chemical reduction and galvanic replacement processes. Benefiting from the abundant carboxyl groups on the surfacecleaved PI, densely and uniformly distributed Ag@Au NPs are successfully prepared on the film under ambient conditions. The high Raman enhancement factor (EF) (up to 1.07 × 10 7 ) and detection capability with low nanomolar (10 −9 M) detection limits are obtained for this flexible SERS sensor. The uniform Raman signals in the random region show good signal homogeneity with a low variation of 8.7%. Moreover, the flexible SERS sensor exhibited superior efficiency and durability after storage for 30 days even after 500 cycles of mechanical stimuli (bending or torsion). The residue of pesticide thiram (tetramethylthiuram disulfide, TMTD) has been rapidly traced by direct sampling from the apple surface, and a sensitivity of 10 ng/cm 2 for TMTD was achieved. These findings show that the PI-based SERS sensor is a very strong candidate for broad and simple utilization of flexible SERS for both laboratory and commercial applications in chemical and biomolecule detections.

Here we demonstrate a simple and effective method of fabricating polymeric scattering substrate for flexible organic light-emitting diodes (OLEDs) that require no costly patterning, etching, or molding processes, aspects that are desirable for the commercialization of large-scale lighting panels. Systematic study of the influences of relative index of refraction, particle size, and doping concentration on transmittance and haze of transparent colorless polyimide (cPI) films was carried out. It was found that the reduction of transmittance and haze of the doped films decreases along with the decrease of the difference of refractive index between the particles and polymer matrix, and it could be compensated by the increase of particle size or doping concentration.

Donor–acceptor alternating copolymers with chlorine atoms on the backbone are synthesized via a straightforward Stille polycondensation. Thiophene and chlorine‐substituted 2,3‐diphenylquinoxaline are chosen as the donor and acceptor moieties, respectively. Compared with the corresponding non‐substituted and fluorine‐substituted analogues, which are also synthesized for systematical studies, the chlorine‐bearing copolymer exhibits the deepest lowest unoccupied molecular orbital (LUMO). The highest occupied molecular orbital (HOMO) level of the chlorine‐bearing copolymer can be modified by applying different donor moieties. Additionally, these chlorine‐bearing copolymers show low self‐absorption and large Stokes Shift.