Fine control and direct monitoring of the spin crossover properties driven by pressure at room temperature are reported for the porous three-dimensional coordination polymer {Fe(pz)[Pt(CN) 4 ]} by using a homemade pressure cell that transforms a DC voltage into pressure. The pressure induced spin state switching is steadily driven through a piezoelectric ceramic element, which transforms the voltage 1−4 kV in pressures in the 0.001−0.035 GPa range. At the same time, the spin state is easily monitored through changes in the optical spectra of the title compound. The results demonstrate that {Fe(pz)[Pt(CN)4]} responds to as small pressure variations as 0.001 GPa (10 atm), thereby proving its efficacy to work as an effective pressure sensor.

Knowledge of the structure in amorphous dioxides is important in many fields of science and engineering. Here we report new experimental results of high-pressure polyamorphism in amorphous TiO 2 (a-TiO 2 ). Our data show that the Ti coordination number (CN) increases from 7.2 ± 0.3 at ∼16 GPa to 8.8 ± 0.3 at ∼70 GPa and finally reaches a plateau at 8.9 ± 0.3 at ≲86 GPa. The evolution of the structural changes under pressure is rationalized by the ratio (γ) of the ionic radius of Ti to that of O. It appears that the CN ≈ 9 plateau correlates with the two 9-fold coordinated polymorphs (cotunnite, Fe 2 P) with different γ values. This CN−γ relationship is compared with those of a-SiO 2 and a-GeO 2 , displaying remarkably consistent behavior between CN and γ. The unified CN−γ relationship may be generally used to predict the compression behavior of amorphous AO 2 compounds under extreme conditions.

Broadband self-trapped exciton (STE) emission in two-dimensional (2D) perovskites is attracting intense attention due to its promising solid-state lighting application. However, few studies have focused on the evolution of the...

Two types of experiments conducted to investigate the effect of pressure on the spin crossover (SCO) properties of the 2D Fe­(II) coordination polymer formulated {Fe­[bipy­(ttr)2]} n are reported, namely, (1) magnetic measurements performed at variable temperature and at fixed pressure and (2) visible spectroscopy at variable pressure and fixed temperature. The magnetic experiments carried out under a hydrostatic pressure constraint of 0.04, 0.08, and 0.8 GPa reveal a two-step spin transition behavior. The characteristic critical temperatures of the spin transition are shifted upward in temperature as pressure increases. The slope of the straight-line of the T c vs P plot, dT c/dP, is 775 K/GPa and 300 K/GPa, for the high temperature and the low temperature steps, respectively. These values are remarkably large and denote the extreme sensitivity of the material to the application of pressure. Indeed, the visible spectroscopic measurements performed at 293 K show that a complete spin transition is induced at pressures as low as 0.4 GPa. Moreover, the pressure-induced spin transition is reversible and shows an asymmetric hysteresis. An analysis of the cooperative interactions of the thermal- and pressure-induced spin transition in the framework of the model of elastic interactions reveals that the elastic energy of the lattice as well as the interaction parameter between the SCO centers change during the course of the spin transition. Consequently, the character of the spin transition varies from abrupt for the high temperature step to continuous for the low temperature step.

Silicon is a long-standing photosensitive material because of its unique photoelectronic properties and mature manufacturing technology. However, silicon photodetectors are generally limited by weak photoresponse in the near-infrared region. In this work, pressure is used as an effective means of tuning the photoresponse of silicon, specifically in the near-infrared region. Silicon has two different types of photoresponse under pressure. In the pressure range from 1 atm to 10 GPa, huge pressure-enhanced photocurrent is observed under illumination by a xenon lamp and near-infrared light (1064 nm). At 10 GPa, the photocurrent density ( Jph), responsivity ( R), and external quantum efficiency are increased 40-fold from those at 1.2 GPa. Interestingly, above 10 GPa, a unique pressure-induced positive–negative photoresponse switch is found along with the phase transformation from the semiconductive phase (Si I) to the metallic phase ( β-tin). Further experiments show that the photothermal effect is the main factor for negative photoresponse. All these pressure-induced properties give silicon more possibilities in the further design of visible and infrared photodetectors.

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Lead-free halide double perovskites (DPs) have been proposed as stable and promising alternatives to lead halide perovskites. Understanding the structural–optical properties of halide DPs is important for their applications. In this study, Cs2AgInCl6 DP nanocrystals, with a direct band gap, were synthesized and studied. Because of a strong electron–phonon coupling leading to exciton self-trapping, a broad emission with a large Stokes shift of Cs2AgInCl6 DP nanocrystals is observed. We observed an abnormal blue-shifted emission accompanied by a red-shifted direct absorption edge because of the reduced electron–phonon coupling under compression in the cubic phase Cs2AgInCl6 DP nanocrystals. Our study clarified the basic structural–optical correlation of halide DPs and may promote their application in related fields.

The past decade has seen enormous interest in emerging photodetectors owing to their diverse applications in daily life and military fields. Tremendous progress has been made in the exploration and optimization of photoelectric materials. In particular, high pressure has been successfully adopted as a significant means to tune photoelectric properties. The remarkable enhancement in photocurrent by several orders of magnitude, induces inverse photoconductivity, and even extends the spectral response range, which was achieved by using the pressure strategy in several functional materials. In this prospective article, recent advances in pressure-regulated photoelectric properties of various functional materials are briefly elaborated on. In addition, the current challenges and possible research directions are discussed. It is sincerely hoped to inspire more new endeavors to promote further investigation of the photoelectric properties of functional materials under high pressure and provide more insights into exploring and optimizing novel photoelectric materials.