Blue‐Light Emissive Type II ZnO@5‐Amino‐2‐Naphthalene Sulfonic Acid Core–Shell Quantum Dots

Blue-light emissive type II [email protected] sulfonic acid (ANSA) core–shell quantum dots (QDs) is first fabricated. Green luminescence (GL) of 2.25 eV ZnO QDs disappears at the threshold excitation wavelengths (λex) > 400 nm due to electronic transition from conduction band (CB) or shallow donor centers VZn2− ≈0.9 above valence (VB). Blue emissions are well elucidated by charge transfer CB lowest unoccupied molecular orbital (LUMO) ANSA and Zn interstitial (Zni) extended Zni states CO, CN, CS (π*)-states, then transitions nonbonding (π) ANSA. Spectral-dependent electron paramagnetic resonance (SDEPR) peak g = 1.96 emerges only with illumination light shorter than in wavelength completely QDs. Electrons trapped Zni's unveiled participate GL defect derive (EPR) ZnO. The estimated spin–spin relaxation time (T2) was about 32.5 ns, which two orders magnitude longer known values for bulk thin-film