新型(4-HBA)SbX_(5)·H_(2)O类钙钛矿单晶及其卤素结构对发光特性的调控

发光材料因其在照明、显示、成像等方面的广泛应用而备受关注。作为新兴发光材料之一,钙钛矿类材料的研究及报道较多。其中,铅基钙钛矿的研究取得了巨大进展,光致发光量子产率(PLQY)几乎达到了100%。然而,基于铅基钙钛矿化学毒性和低稳定性,在实际应用过程中需要特殊的封装,因而提高了生产成本并限制了其实际应用领域。被广泛关注的锡基钙钛矿的荧光量子产率几乎能达到90%,但Sn^(2+)易氧化成Sn^(4+),在空气中极不稳定。相较于铅基钙钛矿和锡基钙钛矿,锑基钙钛矿的低化学毒性、高热稳定性等优点突出。此外,锑基钙钛矿的光学性能在过去几年中也取得了很大的进展,有望突破传统钙钛矿应用的局限。在此,我们报道了一系列新型单晶(4-HBA)SbX_(5)·H_(2)O(4-HBA为4-羟基苄胺缩写,X为Cl或Br)。利用溶剂热法可制备高质量的(4-HBA)SbBr_(5)·H_(2)O、(4-HBA)SbBr_(3)Cl_(2)·H_(2)O和(4-HBA)SbCl_(5)·H_(2)O单晶,以上三个材料均为P-1空间群,Sn^(5+)离子与卤素离子和4-羟基苄胺中的羟基离子形成畸变八面体结构。(4-HBA)SbX_(5)·H_(2)O单晶随着Cl^(-)离子浓度的提高,带隙逐渐增大,光致发光波长从618 nm蓝移到595 nm。随着Cl^(-)的引入,激发态电子由八面体中心的Sn^(5+)离子向羟基的复合路径逐渐被向卤素离子的复合路径取代。Sn^(5+)离子向卤素离子的复合大大提高了发光效率,将荧光寿命从12 ns延长到22 ns,光致发光量子产率(PLQY)提高了近40倍。

On-chip ultrasensitive and rapid hydrogen sensing based on plasmon-induced hot electron-molecule interaction

Hydrogen energy is a zero-carbon replacement for fossil fuels.However,hydrogen is highly flammable and explosive hence timely sensitive leak detection is crucial.Existing optical sensing techniques rely on complex instruments,while electrical sensing techniques usually operate at high temperatures and biasing condition.In this paper an on-chip plasmonic-catalytic hydrogen sensing concept with a concentration detection limit down to 1 ppm is presented that is based on a metal-insulator-semiconductor(MIS)nanojunction operating at room temperature and zero bias.The sensing signal of the device was enhanced by three orders of magnitude at a one-order of magnitude higher response speed compared to alternative non-plasmonic devices.The excellent performance is attributed to the hydrogen induced interfacial dipole charge layer and the associated plasmonic hot electron modulated photoelectric response.Excellent agreements were achieved between experiment and theoretical calculations based on a quantum tunneling model.Such an on-chip combination of plasmonic optics,photoelectric detection and photocatalysis offers promising strategies for next-generation optical gas sensors that require high sensitivity,low time delay,low cost,high portability and flexibility.

Interface charge separation in Cu_(2)CoSnS_(4)/ZnIn_(2)S_(4) heterojunction for boosting photocatalytic hydrogen production

The practical application of hexagonal ZnIn_(2)S_(4)(ZIS)as a visible-light photocatalyst for hydrogen(H_(2))production is hindered by rapid internal charge recombination.In this study,we successfully synthesized Cu_(2)CoSnS_(4)(CCTS)nanocrystals and loaded them onto the surface of ZIS nanosheets to create a p-n heterojunction photocatalyst.The optimized Cu_(2)CoSnS_(4)/ZnIn_(2)S_(4)(CCTS/ZIS)heterojunction exhibited a significantly higher visible-light photo-catalytic H_(2)evolution rate of 4.90 mmol·g^(-1)·h^(-1)compared to ZIS and CCTS alone.The enhanced photocatalytic efficiency was attributed to improved electron transfer and charge separation at the heterojunction interface.The formation of p-n heterojunction facilitated the accumulation of valence band electrons in ZIS and conduction band holes in CCTS,effectively suppressing the recombination of photogenerated electrons and holes.Theoretical calculations,spectroscopic,and photoelectrochemical characterizations supported the findings.This work pre-sents a promising approach for designing efficient p-n heterojunction semiconductor photocatalysts for practical applications in visible-light-driven hydrogen evolution.

Nanostructured materials with localized surface plasmon resonance for photocatalysis

Localized surface plasmon resonance (LSPR) enhanced photocatalysis has fascinated much interest and considerable efforts have been devoted toward the development of plasmonic photocatalysts. In the past decades, noble metal nanoparticles (Au and Ag) with LSPR feature have found wide applications in solar energy conversion. Numerous metal-based photocatalysts have been proposed including metal/semiconductor heterostructures and plasmonic bimetallic or multimetallic nanostructures. However, high cost and scarce reserve of noble metals largely limit their further practical use, which drives the focus gradually shift to low-cost and abundant nonmetallic nanostructures. Recently, various heavily doped semiconductors (such as WO_(3-x), MoO_(3-x), Cu_(2-x)S, TiN) have emerged as potential alternatives to costly noble metals for efficient photocatalysis due to their strong LSPR property in visible-near infrared region. This review starts with a brief introduction to LSPR property and LSPR-enhanced photocatalysis, the following highlights recent advances of plasmonic photocatalysts from noble metal to semiconductor-based plasmonic nanostructures. Their synthesis methods and promising applicability in plasmon-driven photocatalytic reactions such as water splitting, CO_(2) reduction and pollution decomposition are also summarized in details. This review is expected to give guidelines for exploring more efficient plasmonic systems and provide a perspective on development of plasmonic photocatalysis.

Light-induced thermal convection for collection and removal of carbon nanotubes

Carbon nanotubes(CNTs)have exhibited immense potential for applications in biology and medicine,and once their intended purpose is fulfilled,the elimination of residual CNTs is essential to avoid negative effects.In this study,we demonstrated the effective collection and simple removal of CNTs dispersed in a suspension via thermal convection.First,a tapered fiber tip with a cone angle and end diameter of 10°and 3μm,respectively,was fabricated via a heating and pulling method.Further,a laser beam with a power and wavelength of 100 mW and 1.55^m,respectively,was launched into the tapered fiber tip,which was placed in a CNT suspension,resulting in the formation of a microbubble on the fiber tip.The temperature gradient on the microbubble and suspension surface induced thermal convection in the suspension,which resulted in the accumulation of CNTs on the fiber tip.The experimentally formed CNT cluster possessed a circular top surface with a diameter of 87 nm and an arched cross-section with a height of 19μm.Furthermore,this CNT cluster was firmly attached to the fiber tip.Therefore,the removal of CNT clusters can be realized by simply removing the fiber tip from the suspension.Moreover,we simulated the thermal convection that caused CNT aggregation.The obtained results indicate that convection near the fiber tip flows toward it,which pushes the CNTs toward the fiber tip and enables their attachment to it.Further,the flow velocity is symmetrically distributed as a Gaussian function,which results in the formation of a circular top surface and arched cross-sectional profile for the CNT cluster.Our method may be applied in biomedicine for the collection and removal of nano-drug residues.