Small Donor Research Articles

Polymer Acceptors Containing B←N Units for Organic Photovoltaics.

ConspectusOrganic photovoltaics (OPVs), in which blend films of organic or polymer electron donor and electron acceptor are used as the active layer, are a promising photovoltaic technology with the great advantages of solution processing, low cost, and flexibility. The development of small molecular or polymer electron acceptors has boosted power conversion efficiency (PCE) of OPVs from 10% to 18%. Among them, polymer acceptors have the merits of superior morphology stability and excellent mechanical properties. However, owing to the key requirement of very low-lying LUMO/HOMO energy levels for polymer acceptors, very few conjugated polymers can work as polymer acceptors in OPVs. The majority of polymer electron acceptors are based on strong electron-withdrawing imide units or cyano substituents. Since 2015, conjugated polymers containing the boron-nitrogen coordination bond (B←N) have emerged as a new kind of polymer electron acceptor with excellent photovoltaic performance in various kinds of organic photovoltaic devices. In this Account, we summarize our research progress on polymer acceptors containing B←N units.At first, we introduce the principle of B←N to greatly down shift LUMO/HOMO energy levels, which enables B←N to be used to design polymer acceptors. Then we describe the two molecular design strategies for polymer acceptors containing B←N units. For high-efficiency OPVs, polymer acceptors should have wide absorption spectra, proper LUMO/HOMO energy levels, high electron mobility, and good donor/acceptor blend morphology. We discuss how to use molecular design to finely tune the absorption spectra, energy levels, and electron mobility of the B←N-containing polymer acceptors. We also discuss how to improve the phase separation morphology of the blends of these polymer acceptors with small molecular donors or polymer donors. These improvements lead to excellent performance of the polymer acceptors containing B←N units in three kinds of organic photovoltaic devices. The small molecular donor/polymer acceptor type organic solar cells show excellent thermal stability and PCE of 8.0%, which is the highest value reported so far. The all-polymer solar cells exhibit PCE of 10.1%. The all-polymer indoor photovoltaics show PCE as high as 27.4% under fluorescent lamp illumination at 2000 lx. This PCE is fairly comparable to those of the best organic or inorganic indoor photovoltaics. These results provide a solid foundation for future advances. Finally, we propose that great attention should be paid to further PCE enhancement of OPVs and indoor photovoltaic applications of this new emerging kind of polymer acceptor.

Transplantation of a single kidney from pediatric donors less than 10\u2009kg to children with poor access to transplantation: a two-year outcome analysis

BackgroundAccess to kidney transplantation by uremic children is very limited due to the lack of donors in many countries. We sought to explore small pediatric kidney donors as a strategy to provide transplant opportunities for uremic children.MethodsA total of 56 cases of single pediatric kidney transplantation and 26 cases of en bloc kidney transplantation from pediatric donors with body weight (BW) less than 10 kg were performed in two transplant centers in China and the transplant outcomes were retrospectively analyzed.ResultsThe 1-year and 2-year death-censored graft survival in the en bloc kidney transplantation (KTx) group was inferior to that in the single KTx group. Subgroup analysis of the single KTx group found that the 1-year and 2-year death-censored graft survival in the group where the donor BW was between 5 and 10 kg was 97.7 and 90.0%, respectively. However, graft survival was significantly decreased when donor BW was ≤5 kg (p < 0.01), mainly because of the higher rate of thrombosis (p = 0.035). In the single KTx group, the graft length was increased from 6.7 cm at day 7 to 10.5 cm at 36 months posttransplant. The estimated glomerular filtration rate increased up to 24 months posttransplant. Delayed graft function and urethral complications were more common in the group with BW was ≤5 kg.ConclusionsOur study suggests that single kidney transplantation from donors weighing over 5 kg to pediatric recipients is a feasible option for children with poor access to transplantation.

Synthesis and photovoltaic properties of organic molecules based on difluoroquinoxaline derivatives for OPVs

We designed and synthesized two novel low band gap small molecule donors (M1 and M2) that consist of benzo[1,2-b:4,5-b′]dithiophene as the electron-rich core and 6,7-difluoroquinoxaline as the electron-deficient end-group. M1 and M2 with A-D-A type structure were synthesized via Stille coupling reaction for use in OSCs. The absorption maximum of the M1 and M2 in solid thin films exhibited at 536 and 540 nm and absorption onset at 582 and 592 nm, corresponding to band gaps of 2.31 and 2.10 eV, respectively. Although the absorption of the M1 with branched alkyl chain was blue shifted as compared to M2, the branched alkyl chain in benzodithiophene core provide appropriate solubility to provide good OSC performance.

Design and synthesis of small molecules with difluoroquinoxaline units for OSCs

We designed and synthesized three novel small molecule donors (SM1, SM2 and SM3) that consist of thiophene as the electron-donating end group and 6,​7-​difluoroquinoxaline moiety as a novel electron-withdrawing core group. The organic low band gap molecules with 6,​7-​difluoroquinoxaline and thiophene units were synthesized using Stille coupling to generate SM1, SM2 and SM3. The absorption of SM2 and SM3 in solution was red shifted due to increased conjugation length of added thiophene units. In case of SM2 and SM3, introduction of hexyl chain in terminal thiophene units improve solubility in organic solvent. The maximum absorption peaks of SM1, SM2 and SM3 in solid thin films were at 482, 505 and 518 nm, respectively. SM3 was red shifted as compare to SM2 due to increased π-π stacking of electron donor materials.

Inverted versus direct structure bulk heterojunction organic solar cells involving a triphenylamine-based small molecular donor

Inverted versus direct structure bulk heterojunction organic solar cells involving a triphenylamine-based small molecular donor

Kidney transplantation from small pediatric donors may be feasible to those who developed chronic refractory dialysis hypotension: a single-center experience.

BackgroundChronic refractory dialysis hypotension (CRDH) is a serious issue in dialysis patients waiting for transplants. It leads to fatal clinical outcomes and disqualification from kidney transplantation. Kidney transplantation from pediatric donor to adult patient with lower blood pressure (BP) may be an option. No related study has been reported and we conducted this study to first evaluate the effect of pediatric donor kidney transplantation in CRDH recipients.MethodsTen single-kidney transplantations from small pediatric donors after cardiac death in our center between August 2016 and April 2018 were described. Half were CRDH recipients (group A) with intradialytic and interdialytic systolic blood pressure (SBP) below 100 mmHg. Each was paired with no-CRDH recipient (control, group B) from the same donor. The operation method of vascular anastomosis and ureterocystoneostomy was the same as that of adult donors. Clinical characteristics, post-operative treatment and outcomes of all recipients were retrieved. Postoperative BP, graft function and size were compared between two groups. The follow-up time was up to April 2019.ResultsThere was no acute rejection (AR), graft loss or death in all recipients after transplantation. Their renal function was recovered despite three transient delayed graft function (DGF). There was no significant difference in serum creatinine (SCr) or graft size (P=0.84, 0.94) after transplantation between two groups. For all CRDH recipients, the postoperative SBP was above 100 mmHg (except one, 90–130 mmHg). The BP one year after transplantation was maintained at 110–125/70–85 mmHg.Conclusionskidney transplantation from small pediatric donors may be feasible to CRDH recipients and their BP may return to normal after transplantation.

The new era for organic solar cells: small molecular donors

The new era for organic solar cells: small molecular donors

Small donor size does not negatively impact outcomes after deceased-donor renal transplantation.

Higher body mass index (BMI) of deceased-donors is associated with poorer outcomes in transplant recipients. The effect of low donor BMI on recipient graft function is not clear. Scientific Registry of Transplant Recipients data on recipients of deceased-donor kidneys from 2000 to 2019 were categorized by donor BMI (donor BMI<18, 18-27, and >27). Primary outcome was death-censored graft survival. The impact of multiple recipient and donor variables, including low donor BMI and the difference between donor and recipient BMI, was evaluated using a multivariate Cox proportional-hazards model. Low BMI donors (LBD) were more likely to be younger, female, and white (all P<.05). LBD were less likely to be Hispanic, diabetic, or have hypertension (all P<.001). LBD recipients were more likely to be younger and female (both P<.001). Low donor BMI was not significantly associated with recipient graft survival. Donor-recipient BMI difference did not correlate with an increased risk of graft failure. Similar results were obtained when donors were classified using body surface area (BSA). Small donor size in terms of BMI or BSA or a large discrepancy between donor and recipient size should not necessarily preclude transplantation of an otherwise acceptable kidney.

High efficiency ternary organic solar cells enabled by compatible dual-donor strategy with planar conjugated structures

Ternary organic solar cells (OSCs) have received extensive attention for improving the power conversion efficiency (PCE) of organic photovoltaics (OPVs). In this work, a novel donor material (ECTBD) consisting of benzodithiophene (BDT) central electron donor unit was developed and synthesized. The small molecular donor has the same central unit as PM6. The addition of ECTBD into PM6:Y6 system could improve the morphology of active blend layer. In addition, ECTBD showed good morphologically compatibility when blending with PM6:Y6 host, resulting in the improvement of fill factor and current density. As a result, the ternary devices based on PM6:ECTBD:Y6 ternary system achieved a highest PCE of 16.51% with fill factor of 76.24%, which was much higher than that of the binary devices (15.7%). Overall, this work provided an effective strategy to fabricate highly efficient ternary organic solar cells through design of the novel small molecular donor as the third component.

Principles of Aggregation-Induced Emission: Design of Deactivation Pathways for Advanced AIEgens and Applications.

Twenty years ago, the concept of aggregation‐induced emission (AIE) was proposed, and this unique luminescent property has attracted scientific interest ever since. However, AIE denominates only the phenomenon, while the details of its underlying guiding principles remain to be elucidated. This minireview discusses the basic principles of AIE based on our previous mechanistic study of the photophysical behavior of 9,10‐bis(N,N‐dialkylamino)anthracene (BDAA) and the corresponding mechanistic analysis by quantum chemical calculations. BDAA comprises an anthracene core and small electron donors, which allows the quantum chemical aspects of AIE to be discussed. The key factor for AIE is the control over the non‐radiative decay (deactivation) pathway, which can be visualized by considering the conical intersection (CI) on a potential energy surface. Controlling the conical intersection (CI) on the potential energy surface enables the separate formation of fluorescent (CI:high) and non‐fluorescent (CI:low) molecules [control of conical intersection accessibility (CCIA)]. The novelty and originality of AIE in the field of photochemistry lies in the creation of functionality by design and in the active control over deactivation pathways. Moreover, we provide a new design strategy for AIE luminogens (AIEgens) and discuss selected examples.

Principles of Aggregation‐Induced Emission: Design of Deactivation Pathways for Advanced AIEgens and Applications

AbstractTwenty years ago, the concept of aggregation‐induced emission (AIE) was proposed, and this unique luminescent property has attracted scientific interest ever since. However, AIE denominates only the phenomenon, while the details of its underlying guiding principles remain to be elucidated. This minireview discusses the basic principles of AIE based on our previous mechanistic study of the photophysical behavior of 9,10‐bis(N,N‐dialkylamino)anthracene (BDAA) and the corresponding mechanistic analysis by quantum chemical calculations. BDAA comprises an anthracene core and small electron donors, which allows the quantum chemical aspects of AIE to be discussed. The key factor for AIE is the control over the non‐radiative decay (deactivation) pathway, which can be visualized by considering the conical intersection (CI) on a potential energy surface. Controlling the conical intersection (CI) on the potential energy surface enables the separate formation of fluorescent (CI:high) and non‐fluorescent (CI:low) molecules [control of conical intersection accessibility (CCIA)]. The novelty and originality of AIE in the field of photochemistry lies in the creation of functionality by design and in the active control over deactivation pathways. Moreover, we provide a new design strategy for AIE luminogens (AIEgens) and discuss selected examples.

COVID-19 convalescent plasma: phase 2.

See editorial on page 1123–1127, in this issue

Hyperbranched conjugated polymers based on 4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole for ternary organic solar cells

A new class of end-modifiable hyperbranched conjugated polymer (HBCP–Br) was synthesized from an AB2 monomer, and the end-modification of HBCP-Br was carried out by substituting the end-Br with a donor group to give the end-modified HBCPs (HBCP-OR). Both polymers had relatively good thermal stability (Td > 350 °C) and deep HOMO energy levels (−5.40 eV for HBCP-OR, −5.45 eV for HBCP-Br). Besides, the other two similar small molecular acceptors (IDTOTZ and IDTCPT) were synthesized to construct ternary organic solar cells (OSCs) with HBCP-OR or HBCP-Br. Owing to the favorable spectral and energy levels matching and relatively regular morphology, the ternary OSCs based on HBCP-OR/IDTOTZ/IDTCPT obtained an optimized PCE of 4.86% (with an open-circuit voltage (VOC) of 0.893 V, a short-circuit current density (JSC) of 11.71 mA, and a fill factor (FF) of 45.18%), which performed better than the devices based on HBCP-Br/IDTOTZ/IDTCPT with a PCE of 2.33%. In addition, the HBCP-Br also exhibited photovoltaic activity when used as acceptors in the ternary OSCs based on small molecular donors, which demonstrated that HBCPs could play different roles in the OSCs.

Structural Control of the Molecular Packing and Dynamics of Mechanofluorochromic Materials Based on Small Donor–Acceptor Systems with Turn‐On Luminescence

AbstractA series of simple donor–acceptor molecules consisting of an oligo‐oxyethylene (OOE) N‐substituted diphenylamine connected to a dicyanovinyl (DCV) acceptor group by a thienyl π‐conjugating spacer are synthesized. Amorphous deep‐red freshly cast thin films rapidly evolve towards an almost colorless pale beige poly‐crystalline stable material from which a deep‐red photoluminescent state can be switched‐on by mechanical stimulation. The effects of the length of the OOE chain on the molecular packing of the material and on the dynamics of the recovery process and aggregation in solution are analyzed. Crystallographic results show that the length of the OOE chain directly controls the molecular packing from head‐to‐tail arrangement of the dipoles for short chain to co‐facial dimers leading to a non‐centrosymmetric material with nonlinear optics (NLO) activity for the longer ones. The analysis of the dynamics of the self‐recovery process of thin films and of molecular aggregation in solution shows that the dynamics of both processes is directly controlled by the length of the OOE chain. Since, as confirmed by optical and electrochemical results, the OOE substituents have strictly no influence on the electronic properties of the π‐conjugated system, the observed effects are unambiguously related to changes in intermolecular interactions.

All-Small-Molecule Organic Solar Cells Based on a Fluorinated Small Molecule Donor With High Open-Circuit Voltage of 1.07 V.

A new small molecule donor with an acceptor-donor-acceptor (A-D-A) structure, namely DRTB-FT, has been designed and synthesized for all-small-molecule organic solar cells (ASM-OSCs). By introducing fluorine atoms on the thienyl substituent of the central benzodithiophene unit, DRTB-FT shows a low-lying highest occupied molecular orbital (HOMO) energy level of −5.64 eV. Blending with an A-D-A type acceptor F-2Cl, DRTB-FT based ASM-OSCs gave a power conversion efficiency (PCE) of 7.66% with a high open-circuit voltage (Voc) of 1.070 V and a low energy loss of 0.47 eV. The results indicate that high Voc of ASM-OSC devices can be obtained through careful donor molecular optimization.

17β-Estradiol as a New Therapy to Preserve Microcirculatory Perfusion in Small Bowel Donors.

Intestine graft viability compromises retrieval in most brain-dead donors. Small bowel transplantation is a complex procedure with worse outcomes than transplantation of other abdominal organs. The hormone 17β-estradiol (E2) has shown vascular protective effects in lung tissue of brain death (BD) male rats. Thus, estradiol might be a treatment option to improve the quality of intestinal grafts. Male Wistar rats were divided into 3 groups (n = 10/group): rats that were trepanned only (sham-operated), rats subjected to rapid-onset BD, and brain-dead rats treated with E2 (280 µg/kg, intravenous) (BD-E2). Experiments performed for 180 minutes thereafter are included: (a) laser-Doppler flowmetry and intravital microscopy to evaluate mesenteric perfusion; (b) histopathological analysis; (c) real-time polymerase chain reaction of endothelial nitric oxide synthase (eNOS) and endothelin-1; (d) immunohistochemistry of eNOS, endothelin-1, P-selectin, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 expression; and (e) ELISA for cytokines and chemokines measurement. 17β-Estradiol improved microcirculatory perfusion and reduced intestinal edema and hemorrhage after BD. The proportions of perfused small vessels were (mean ± scanning electron microscope) BD rats (40% ± 6%), sham-operated rats (75% ± 8%), and BD-E2 rats (67% ± 5%) (P = 0.011). 17β-Estradiol treatment was associated with 2-fold increase in eNOS protein (P < 0.0001) and gene (P = 0.0009) expression, with no differences in endothelin-1 expression. BD-E2 rats exhibited a reduction in vascular cell adhesion molecule 1 expression and reduced cytokine-induced neutrophil chemoattractant 1 and interleukina-10 serum levels. 17β-Estradiol was effective in improving mesenteric perfusion and reducing intestinal edema and hemorrhage associated with BD. The suggestion is that E2 might be considered a therapy to mitigate, at least in part, the deleterious effects of BD in small bowel donors.

COVID-19: A global transplant perspective on successfully navigating a pandemic.

The COVID‐19 pandemic has rapidly evolved and changed our way of life in an unprecedented manner. The emergence of COVID‐19 has impacted transplantation worldwide. The impact has not been just restricted to issues pertaining to donors or recipients, but also health‐care resource utilization as the intensity of cases in certain jurisdictions exceeds available capacity. Here we provide a personal viewpoint representing different jurisdictions from around the world in order to outline the impact of the current COVID‐19 pandemic on organ transplantation. Based on our collective experience, we discuss mitigation strategies such as donor screening, resource planning, and a staged approach to transplant volume considerations as local resource issues demand. We also discuss issues related to transplant‐related research during the pandemic, the role of transplant infectious diseases, and the influence of transplant societies for education and disseminating current information.

Highly Efficient All-Small-Molecule Organic Solar Cells with Appropriate Active Layer Morphology by Side Chain Engineering of Donor Molecules and Thermal Annealing.

It is very important to fine-tune the nanoscale morphology of donor:acceptor blend active layers for improving the photovoltaic performance of all-small-molecule organic solar cells (SM-OSCs). In this work, two new small molecule donor materials are synthesized with different substituents on their thiophene conjugated side chains, including SM1-S with alkylthio and SM1-F with fluorine and alkyl substituents, and the previously reported donor molecule SM1 with an alkyl substituent, for investigating the effect of different conjugated side chains on the molecular aggregation and the photophysical, and photovoltaic properties of the donor molecules. As a result, an SM1-F-based SM-OSC with Y6 as the acceptor, and with thermal annealing (TA) at 120 °C for 10 min, demonstrates the highest power conversion efficiency value of 14.07%, which is one of the best values for SM-OSCs reported so far. Besides, these results also reveal that different side chains of the small molecules can distinctly influence the crystallinity characteristics and aggregation features, and TA treatment can effectively fine-tune the phase separation to form suitable donor-acceptor interpenetrating networks, which is beneficial for exciton dissociation and charge transportation, leading to highly efficient photovoltaic performance.

Polymeric persulfide prodrugs: Mitigating oxidative stress through controlled delivery of reactive sulfur species.

Related biologically to the known gasotransmitter hydrogen sulfide (H2S), persulfides (R-SSH) have recently been recognized as native signaling compounds and redox regulators in their own right. Reported here is the synthesis, characterization, and in vitro evaluation of a small molecule persulfide donor and its polymeric counterpart, both of which release N-acetyl cysteine persulfide (NAC-SSH) in response to esterases. The donors, termed EDP-NAC and poly(EDP-NAC), underwent controlled decomposition in response to porcine liver esterase, resulting in pseudo-first-order release half-lives of 1.6 h ± 0.3 h and 36.0 h ± 0.6 h, respectively. In cell experiments, slow-releasing poly(EDP-NAC) rescued H9C2 cardiomyocytes more effectively than EDP-NAC when cells were treated with 5-fluorouricil (5-FU), which induces sustained production of ROS. Neither EDP-NAC nor poly(EDP-NAC) rescued MCF-7 breast cancer cells from 5-FU-induced oxidative stress, suggesting that polymeric persulfide donors could be used as adjuvants to reduce the deleterious cardiotoxic effects of many chemotherapeutics.

Lanthanide doping of AIIIBV crystals

The state of rare earth impurities at concentrations of about 1018 cm−3 in volume-doped AIIIBV semiconductor crystals can be described in the framework of the model of quasi-molecular rare earth centers of Ln2O3 type and spontaneous polarization regions-coupled spin-polarons localized on small donors.