Formamidinium Lead Bromide (FAPbBr_3) Perovskite Microcrystals for Sensitive and Fast Photodetectors

Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH_2)_2 PbX_3(FAPbX_3), it has been considered to be a better optoelectronic material than conventional CH_3NH_3-PbX_3(MAPbX_3). Herein, we fabricated a FAPbBr_3 microcrystal-based photodetector that exhibited a good responsivity of 4000 A W-1 and external quantum efficiency up to 106% under one-photon excitation, corresponding to the detectivity greater than 1014 Jones. The responsivity is two orders of magnitude higher than that of previously reported formamidinium perovskite photodetectors. Furthermore, the FAPbBr_3 photodetector's responsivity to two-photon absorption with an 800-nm excitation source can reach 0.07 A W^(-1), which is four orders of magnitude higher than that of its MAPbBr_3 counterparts. The response time of this photodetector is less than 1 ms.This study provides solid evidence that FAPbBr_3 can be an excellent candidate for highly sensitive and fast photodetectors.

Vibrationally Resolved Electronic Spectra of 7,8-Benzoquinoline: Franck-condon Simulation Including Herzberg-Teller and Duschinsky Effects

In harmonic approximation,the vibrationally resolved S1?S0 electronic absorption and emission spectra of 7,8-benzoquinoline were simulated using the Franck-Condon approximation including the Herzberg-Teller and Duschinsky effects,and the results reproduced the experimental spectra very well.Our calculations show that the Herzberg-Teller effect and the Duschinsky mixing play key role in simulating correctly the weak or forbidden transition like the S1?S0 bands of 7,8-benzoquinoline,especially the former.Based on the present theoretical results,we tentatively assigned a few bands which were not unambiguously marked in the experimental spectra.Comparing the vibrationally resolved electronic spectra of 7,8-benzoquinoline with that of phenanthrene simulated in the previous study,the increased vibronic activity of 7,8-benzoquinoline is due to the symmetry break,which is caused by the introduction of N-heteroatom into the aromatic ring of phenanthrene.

Research advancement of DNA-based intelligent hydrogels:Manufacture, characteristics, application of disease diagnosis and treatment

DNA-based hydrogels are exceptional materials for biological applications because of their numerous advantages such as biodegradability,biocompatibility,hydrophilicity,super absorbency,porosity,and swelling.Among these advantages,the ability of DNA-based hydrogels to respond to specific physical and chemical triggers and undergo reversible phase transitions has garnered significant attention in the fields of disease diagnosis(biosensors)and treatment(drug delivery).This article focuses on the recent advancements in the research of DNA-based hydrogels and discusses the different types of these hydrogels,the synthetic methods,their unique properties,and their applications in biosensors and drug delivery.The types of DNA hydrogels are categorized based on their building blocks,and the process of synthesis as well as the unique characteristics of DNA-based hydrogels are described.Then,DNA-based responsive hydrogels utilized as intelligent materials for the development of biosensors are reviewed.Furthermore,this article also presents the current status of DNA-based responsive hydrogels in drug delivery for cancer treatment,wound healing,and other therapeutic applications.Ultimately,this paper discusses the current challenges in expanding the practical application of DNA-based hydrogels.

Hierarchically spacing DNA probes on bio-based nanocrystal for spatial detection requirements

Sterically spacing and locating functional matters at the nanoscale exert critical effects on their application,especially for the fluorescence probes whose aggregation causes emission quenching.Here we achieved a hierarchical spacing strategy of DNA fluorescence probes for ion detection via locating them separately on rod-like cellulose nanocrystals(CNCs)and further isolating CNCs by pre-grafting long molecular chains.Controlling chemical structure of CNC and location degree could adjust the interspace of DNA probes(with a molecular length of ca.3.6 nm)in a range of 3.5-6.5 nm with a gradient about 0.2 nm.A length up to micrometer scale of the CNC nanorods was necessary to provide DNA probes with well-separated grafting locations and enough freedom,which brought a vast linear detection range from 10 nmol/L to 5 μmol/L of Hg^2+ concentration.The abundant reactive sites on CNC allowed a grafting pre-location of poly(tert-butyl acrylate)(PtBA)to promote the isolation of DNA probes.Controlled radical polymerization was employed to adj ust the length of PtBA molecular chains,which increased the linear sensitivity coefficient of Hg^2+ detection by ca.2.5 times.This hierarchical nanoscale spacing concept based on chemical design can hopefully cond uce to the development of biosensor and medical diagnosis.A hierarchical spacing strategy was applied to separate DNA fluorescent probes on CNCs and detect ion concentration linearly.The first-level spacing was to locate probes uniformly on CNCs,obtaining a wide linear range;and the second-level spacing was to isolate CNCs with polymer,obtaining an increased linear coefficient.

Sensitive semi-quantitative detection of respiratory syncytial virus by dark-field light scattering imaging of the infected host cells

A novel sensitive semi-quantitative virus detection technique was developed using the respiratory syncytial virus(RSV) as an example, through dark-field light scattering imaging of the surface state of the virusinvaded host cells. In this method, anti-RSV-antibody modified gold nanoparticles(Au NPs) could bind with the invading virus on the cell membrane of the infected host cells through the specific antibody-antigen binding. Then,the host cells could be imaged by the localized surface plasmon resonance light scattering properties of Au NPs under a dark-field light scattering microscopy, which could be further used to semi-quantify the invading virus.

Hybridization chain reaction triggered controllable one-dimensional assembly of gold nanoparticles

Assembling and ordering nanomaterials into desirable patterns are considerably significant,since the properties of nanomaterials depend not only on the size and shape,but also on the spatial arrangement among the collective building blocks.In this work,the DNA self-assembly technology of hybridization chain reaction(HCR) provided a convenient method to yield long double-strand DNA(dsDNA) to install gold nanoparticles(AuNPs) into one dimensional assembly along the skeleton of dsDNA.Interestingly,the tunable length of AuNPs assemblies along dsDNA chain could be achieved by adjusting the reaction time of HCR,which is based on the formation of covalent bond between Au and the-SH group of DNA.Compared with weak light scattering of single AuNP,these AuNPs assemblies could be clearly imaged under the dark field microscopy,indicating that the light scattering was greatly improved after assembling.

Drugging the undruggable molecules by a DNA nanorobot

Using synthetic nanorobots to efficiently and safely execute therapeutic functions in human bodies is a long-standing dream.In the recent issue of Nature Biotechnology,a paper describes the latest development in such an attempt to implement an autonomous DNA robot in cancer therapy[1].Upon being injected into animals,the DNA nanorobots can find and destroy life-threatening tumors.