RESUMO
This paper describes the mechanisms of charge recombination on both the nanosecond and microsecond time scales in a donor-acceptor system comprising thiol-modified bis(diarylamino)4,4'-biphenyl (TPD) molecules attached to a CdS quantum dot (QD) via the thiolate linker. Transient absorption measurements, in conjunction with EPR and magnetic field effect studies, demonstrate that recombination on the nanosecond time scale is mediated by radical pair intersystem crossing (RP-ISC), as evidenced by the observation of a spin correlated radical ion pair, the formation of the localized (3)*TPD state upon charge recombination, and the sensitivity of the yield of (3)*TPD to an applied magnetic field. These experiments show that the radical spins of the donor-acceptor system have weak magnetic exchange coupling (|2J| < 10 mT) and that the electron donated to the QD is trapped in a surface state rather than delocalized within the QD lattice. The microsecond-time scale recombination is probably gated by diffusion of the trapped electron among QD surface states. This study demonstrates that magneto-optical studies are useful for characterizing the charge-separated states of molecule-QD hybrid systems, despite the heterogeneity in the donor-acceptor geometry and the chemical environment of the radical spins that is inherent to these systems.
RESUMO
A 62-year-old woman with a history of moderate myopia, long-standing open-angle glaucoma (OAG), and Fuchs dystrophy in both eyes was referred for consultative care. She had prior trabeculectomy in 1984 and 1992 in the left and right eyes, respectively. She is 3 months post-Descemet-stripping endothelial keratoplasty (DSEK) in the left eye, now referred with uncontrolled intraocular pressure (IOP) despite maximum tolerated medical therapy. Current medical therapy for IOP consists of acetazolamide 250 mg by mouth 2 times a day, brimonidine 2 times a day in the left eye, dorzolamide 2 times a day in the left eye, and timolol 2 times a day in the left eye. The patient has a history of presumed steroid response; however, her corneal surgeon has requested that the steroid be continued for the next several months because of the recent DSEK. The IOP in the left eye has ranged from the mid-20s to mid-30s since DSEK. The right eye has consistently had pressure in the low teens and below for many years without topical antihypertensive medications. Examination revealed stable visual acuity at 20/30 and 20/40 in the right and left eyes, respectively, IOP was 12 mm Hg in the right eye and 25 mm Hg in the left eye by Goldman applanation, irregular but reactive pupils without afferent defect, and full confrontational visual fields. Slitlamp examination showed superior low avascular bleb, moderate-to-severe guttae, and posterior chamber IOL in the right eye. The left eye showed superior low diffuse bleb, clear DSEK graft, quiet chamber, superonasal iridectomy, and posterior chamber IOL with an open posterior capsule. The conjunctiva was moderately scarred but a repeat trabeculectomy or Xen Gel stent (Abbvie) appeared possible. The angles were wide open in each eye. Fundus examination was normal aside from myopic, anomalous-appearing nerves with an approximate cup-to-disc ratio of 0.90 in both eyes. Humphrey visual field showed nonspecific changes on the right and moderate nasal defect on the left eye, stable to previous examinations dating back to 2018 (Figure 1JOURNAL/jcrs/04.03/02158034-202407000-00018/figure1/v/2024-07-10T174240Z/r/image-tiff and Figure 2JOURNAL/jcrs/04.03/02158034-202407000-00018/figure2/v/2024-07-10T174240Z/r/image-tiff). Optical coherence tomography (OCT) of the retinal nerve fiber layer (RNFL) revealed moderated thinning in both eyes that was also stable to prior examinations (Figure 3JOURNAL/jcrs/04.03/02158034-202407000-00018/figure3/v/2024-07-10T174240Z/r/image-tiff). Her axial length measured 25.23 and 26.34 mm in the right and left eyes, respectively. Central corneal thickness was 553 µm in the right eye and 563 µm in the left eye before her DSEK procedure. What would be your approach to management of this patient's left eye, addressing the following: Rationale for your procedure of choice? Would you over-rule the corneal surgeon and stop the steroid in an attempt to obviate the need for glaucoma surgery? Does the age of onset of glaucoma affect your surgical decision making? Note that patient age at the time of trabeculectomy was 22 years. Are some procedures better suited for patients after DSEK surgery?