Cesium Cations Research Articles

Replacing cesium with formamidinium cation in colloidal perovskite nanoplatelets: Synthetic alloying and post-synthetic cation exchange towards efficient blue emission

Blue-emitting perovskite materials have attracted remarkable attention in recent years owing to their potential in full-color display and lighting applications. Two-dimensional (2D) perovskite nanoplatelets (NPls) are considered as competitive blue emitters due to high carrier recombination probability and good spectrum stability compared with their mixed-halide counterparts. However, the 2D nature and high defect density of perovskite NPls generally result in nonradiative carrier recombination, making it problematic for achieving efficient blue emission. Herein, we reported a novel way to enhance the blue emission efficiency of perovskite NPls. We found that by using formamidinium cation (FA+) to replace the cesium cation (Cs+) during NPls synthesis, the photoluminescence (PL) of the NPls can be significantly enhanced. The PL quantum yield (PLQY) of NPls exhibited a monoclinic rising tendency with increased FA+ content, and the FAPbBr3 NPls finally show efficient deep blue emission at 433 nm with PLQY up to 70% as well as narrow emission bandwidth of only 12 nm. We further demonstrated that efficient blue emission can be realized not only by FA+ alloying but also by post-synthetic treatment of the as-synthesized CsPbBr3 NPls using FA+, where the FA+ was capable to replace the Cs+ in perovskite NPls through cation exchange. Resultantly, PLQY as high as 90% was achieved at a pure blue wavelength of 457 nm. Our work provides a promising strategy for achieving efficient and color-pure blue-emitting perovskite materials, which could potentially further promote their light-emitting applications.

Synthesis and Structure of Iron(III) Malonates with Rubidium and Cesium Cations

Synthesis and Structure of Iron(III) Malonates with Rubidium and Cesium Cations

On water reorientation dynamics in cation hydration shells

The effects of ions on liquid water’s structural, dynamical, and thermodynamical properties have key implications for a wide range of biological and technological processes. Based on simulations and analytic modeling, we have recently developed a framework that rationalizes the effects of solutes and interfaces on water reorientation dynamics. However, this picture still misses some contributions of the cations to the experimentally measured slowdown or acceleration of water dynamics. All-atom classical simulations also face some limitations in quantitatively reproducing water structural and dynamical features in ionic aqueous solutions. Here, we show that a scaled-charge approach can successfully reproduce experimental trends and that ab initio descriptions are not required. We show that a picture where the cation would lock a water molecule dipole and lead to partial OH reorientation is both incorrect for some ions, and largely exaggerated for others. We demonstrate that a combination of two effects on the hydrogen-bond (H-bond) exchange dynamics explains the ambient temperature acceleration of water reorientation next to a cesium cation, and the retardation next to lithium and magnesium cations. First, ions create a local excluded volume, which hinders the approach of possible new H-bond partners, leading to a retarding contribution. However, they also perturb the local water structure, reducing the energetic cost of elongating the initial H-bond. For magnesium and lithium cations, the excluded volume effect dominates, which leads to an overall retardation of the H-bond exchange. For the cesium cation, at room temperature, this latter contribution overcomes the excluded volume effect, leading to an acceleration; moreover, the strong temperature dependence observed in the experiments, going from a large acceleration close to freezing to a retardation close to boiling, is understood by the key enthalpic effect of the elongation contribution. Overall, our framework now provides a comprehensive understanding of cations’ and anions’ effects on water reorientation dynamics.

Quasi‐2D Hybrid Perovskite Formation Using Benzothieno[3,2‐b]Benzothiophene (BTBT) Ammonium Cations: Substantial Cesium Lead(II) Iodide Black Phase Stabilization

Abstract3D hybrid perovskites (APbX3) have made a significant impact on the field of optoelectronic materials due to their excellent performance combined with facile solution deposition and up‐scalable device fabrication. Nonetheless, these materials suffer from environmental instability. To increase material stability, the organic cation (A) is substituted by the non‐volatile cesium cation. However, the desired photoactive cesium lead(II) iodide black phase is metastable in ambient conditions and spontaneously converts into the photo‐inactive yellow δ‐phase. In this work, the black phase is stabilized by the formation of a quasi‐2D perovskite containing a benzothieno[3,2‐b]benzothiophene (BTBT) large organic ammonium cation. Thermal analysis shows that degradation of the butylammonium (BA)‐based quasi‐2D perovskite (BA)2CsPb2I7 sets in at ≈130 °C, while (BTBT)2CsPb2I7 is phase‐stable until ≈230 °C. Additionally, the (BTBT)2CsPb2I7 film does not show any sign of degradation after exposure to 77% Relative Humidity in the dark for 152 days, while (BA)2CsPb2I7 degrades in a single day. Photoconductor‐type detectors based on (BTBT)2CsPb2I7 demonstrate an increased external quantum efficiency and a similar specific detectivity compared to the BA‐based reference detectors. The results demonstrate the utility of employing a BTBT cation within the organic layer of quasi‐2D perovskites to significantly enhance the stability while maintaining the optoelectronic performance.

Electrostatic Tuning of Ionic Charge in SiO2 Dielectric Thin Films

Dielectric thin films are a fundamental part of solid-state devices providing the means for advanced structures and enhanced operation. Charged dielectrics are a particular kind in which embedded charge is used to create a static electric field which can add functionality and improve the performance of adjacent electronic materials. To date, the charge concentration has been limited to intrinsic defects present after dielectric synthesis, unstable corona charging, or complex implantation processes. While such charging mechanisms have been exploited in silicon surface passivation and energy harvesters, an alternative is presented here. Solid-state cations are migrated into SiO2 thin films using a gateless and implantation-free ion injecting method, which can provide greater long-term durability and enable fine charge tailoring. We demonstrate the migration kinetics and the stability of potassium, rubidium, and caesium cations inside of SiO2 thin films, showing that the ion concentration within the film can be tuned, leading to charge densities between 0.1–10 × 1012 q cm−2. A comprehensive model of ion injection and transport is presented along a detailed investigation of the kinetics of alkali cations. Integrating ionic charge into dielectrics to produce controlled electric fields can enable new architectures where field effect is exploited for improved electron devices.

Front Cover: The Cesium Oxide Mercuride Cs18Hg8O6 (Z. Anorg. Allg. Chem. 10/2022)

The cover picture shows crystal structure and electronic structure of the compound Cs18Hg8O6. It contains the first isolated mercuride anions, cubic [Hg8]6− entities which are coordinated by Cesium cations. As further anions oxide anions O2− are present in the structure and form a 3D scaffolding network of [Cs6O] octahedra. The ′mercubanide′ anions are arranged in a cubic body-centered topology. The calculated electronic structure is shown as a spaghetti representation. The energy bands below the Fermi level can be attributed to either mercuride or oxide anions, emphasizing the picture of an ionic double salt. The mercuride Cs18Hg8O6 complements a series of compounds with anions from relativistic atoms, showing peculiar features of the chemical bonding. Below, a photograph shows a typical rod-shaped crystal with dark metallic luster.(DOI: 10.1002/zaac.202100389).

Cesium trifluoroacetate induced synergistic effects of grain growth and defect passivation on high-performance perovskite solar cells

The prejudicial defects accumulated at the grain boundaries and surface are one of the most important reasons that cause perovskite solar cells (PSCs) to deviate from the theoretical Shockley–Queisser efficiency limit and poor stability. Consequently, it is highly desirable to reduce defect densities of the polycrystalline perovskite film through manipulating perovskite crystallization and introducing passivation strategy. Herein, the synergistic effects of cesium trifluoroacetate (Cs-TFA) as a novel additive are demonstrated, where it not only provides cesium cations (stabilizer) for perovskite lattice, but also can simultaneously modulate crystal growth and passivate grain boundaries defects. The resultant perovskite films possess more regular morphology, larger grain sizes, and lower defect density. The enlarged crystal grains derive from the incorporation of Cs-TFA that slows down nucleation process, which is demonstrated by in-situ laser confocal photoluminescence imaging. As a result, the encouraging efficiency up to 22.82% is realized for the resulting optimized device. Additionally, the unencapsulated devices sustain around 91% of its initial efficiency after storing 850 h in the air with 40–45% relatively humidity (R.H.) under dark.

Stabilized High-Membered and Phase-Pure 2D All Inorganic Ruddlesden-Popper Halide Perovskites Nanocrystals as Photocatalysts for the CO2 Reduction Reaction.

In contrast to the 2D organic-inorganic hybrid Ruddlesden-Popper halide perovskites (RPP), a new class of 2D all inorganic RPP (IRPP) has been recently proposed by substituting the organic spacers with an optimal inorganic alternative of cesium cations (Cs+ ). Nevertheless, the synthesis of high-membered 2D IRPPs (n>1) has been a very challenging task because the Cs+ need to act as both spacers and A-site cations simultaneously. This work presents the successful synthesis of stable phase-pure high-membered 2D IRPPsof Csn+1 Pbn Br3n+1 nanosheets (NSs) with n= 3 and 4 by employing the strategy of using additional strong binding bidentate ligands. The structures of the 2D IRPPs (n= 3 and 4) NSs are confirmed by powder X-ray diffraction and high-resolution aberration-corrected scanning transmission electron microscope measurements. These 2D IRPPs NSs exhibit a strong quantum confinement effect with tunable absorption and emission in the visible light range by varying their n values, attributed to their inherent 2D quantum-well structure. The superior structural and optical stability of the phase-pure high-membered 2D IRPPs make them a promising candidate as photocatalysts in CO2 reduction reactions with outstanding photocatalytic performance and long-termstability.

Polyoxomolybdate Layered Crystals Constructed from a Heterocyclic Surfactant: Syntheses, Pseudopolymorphism and Introduction of Metal Cations.

Crystals with layered structures are crucial for the construction of functional materials exhibiting intercalation, ionic conductivity, or emission properties. Polyoxometalate crystals hybridized with surfactant cations have distinct layered packings due to the surfactants which can form lamellar structures. Introducing metal cations into such polyoxometalate-surfactant hybrid crystals is significant for the addition of specific functions. Here, polyoxomolybdate–surfactant hybrid crystals were synthesized as single crystals, and unambiguously characterized by X-ray structure analyses. Octamolybdate ([Mo8O26]4–, Mo8) and heterocyclic surfactant of 1-dodecylpyridinium (C12py) were employed. The hybrid crystals were composed of α-type and β-type Mo8 isomers. Two crystalline phases containing α-type Mo8 were obtained as pseudopolymorphs depending on the crystallization conditions. Crystallization with the presence of rubidium and cesium cations caused the formation of metal cation-introduced hybrid crystals comprising β-Mo8 (C12py-Rb-Mo8 and C12py-Cs-Mo8). The yield of the C12py-Rb-Mo8 hybrid crystal was almost constant within crystallization temperatures of 279–303 K, while that of C12py-Cs-Mo8 decreased over 288 K. This means that the C12py-Mo8 hybrid crystal can capture Rb+ and Cs+ from the solution phase into the solids as the C12py-Rb-Mo8 and C12py-Cs-Mo8 hybrid crystals. The C12py-Mo8 hybrid crystals could be applied to ion-capturing materials for heavy metal cation removal.

The Cesium Oxide Mercuride Cs18Hg8O6

AbstractBy reacting Cs with Cs2O and elemental mercury the new double salt Cs18Hg8O6 could be obtained. Its crystal structure (cubic, space group I23 with a=13.3920(10) Å, Z=2, R1=0.026/0.032 for I≥2σ(I)/all I, respectively) comprises isolated oxide anions in octahedral coordination by cesium cations next to the mercuride anion [Hg8]6−. This first isolated anion of mercury has cubic shape and is coordinated by cesium atoms capping the faces and the edges of the [Hg8]6− cube. The ionic character of the double salt is shown in DFT calculations of the electronic structure. Raman spectra show distinct features in the low energy region arising from the vibrations of the mercuride anion. Cs18Hg8O6 has very close structural analogies to the thallide oxide Cs18Tl8O6.

Impact of Cesium Concentration on Optoelectronic Properties of Metal Halide Perovskites.

Performance of a perovskite solar cell is largely influenced by the optoelectronic properties of metal halide perovskite films. Here we study the influence of cesium concentration on morphology, crystal structure, photoluminescence and optical properties of the triple cation perovskite film. Incorporation of small amount (x = 0.1) of cesium cations into Csx(MA0.17FA0.83)1−x Pb(I0.83Br0.17)3 leads to enhanced power conversion efficiency (PCE) of the solar cell resulting mainly from significant rise of the short-current density and the fill factor value. Further increase of Cs concentration (x > 0.1) decreases the film’s phase purity, carrier lifetime and correspondingly reduces PCE of the solar cell. Higher concentration of Cs (x ≥ 0.2) causes phase segregation of the perovskite alongside with formation of Cs-rich regions impeding light absorption.

High-efficiency perovskite photovoltaic modules achieved via cesium doping

By using the Cs-doped MAPbI 3 as the model perovskite materials, several effects arising from the doping of Cs + into hybrid perovskites have been summarized. Significantly, a suppression of ion migration effects and an improvement in the diffusion length were observed. The Cs + doped PSCs showed hysteresis-free behavior, device efficiency boosted from 19.73% to 21.72%, and the fabricated modules (6.5 cm × 7 cm) with a high PCE of 21.08% via “non-destructive replicate” of all photovoltaic parameters from small device. • Cs-doped MAPbI 3 acts as the model perovskite materials. • Doping of Cs + into hybrid perovskites significantly suppresses ion migration. • Cs + doping noticeably increases the carrier diffusion length of the perovskite film. • The Cs + doped PSCs showed hysteresis-free behavior. • Fabricated cell efficiency reached 21.72%, and module over 21.08% Perovskite solar modules have been attracting increasing attention due to their market potential, yet publications concerned with theintrinsic scale-up potential of different perovskite compositions remain relatively scarce. On the other hand, while great success is being made towards improving the power conversion efficiency ( PCE ) of perovskite solar cells (PSCs) by cesium cation (Cs + ) doping of the perovskite, more attention is being paid to the perovskite phase stabilization effect of Cs + doping, and less to other properties that are critical to understand and futher improve the PSC’s. In this work, moderately-Cs-doped MAPbI 3 was employed as a model perovskite material in order to exclude the phase stabilization effect. Our systematic study revealed the influence of Cs + in organic–inorganic hybrid perovskites on the crystal structure, crystallization process, trap state density, band structure and charge (i.e. , ions or photo-carriers) transport. Markedly, it has been observed that Cs + doping can greatly increase the carrier diffusion length in the perovskite films, thus improving the potential to scale-up PSC’s.The PCE of small area devices (0.09 cm 2 ) was increased to 21.72% from 19.73%, with decreased hysteresis behavior and increased operational stability (T 85 = 1000 h) after Cs + doped, where T 85 refers to the retention of 85% of the initial PCE . Moreover, a PCE of 21.08% was obtained for a Cs + -containing perovskite module with an active area > 30 cm 2 , which demonstrates a better “reproducibility” than the reference sample (MAPbI 3 -based perovskite modules, PCE = 18.26%).

Selective strontium adsorption using synthesized sodium titanate in aqueous solution

Amorphous sodium titanates were synthesized using a mid-temperature sol–gel method for evaluation as selective adsorbents of strontium in the presence of cesium or metal cations (Al3+, Mg2+, Ca2+, and Mn2+) from aqueous solution. Synthesized sodium titanate showed high adsorption capacity and selectivity for strontium. The maximum adsorption capacity of strontium by sodium titanate was 193.93 mg g−1 in aqueous solution containing an initial concentration of 5 mM (438.60 mg L−1) strontium and 5 mM (666.67 mg L−1) cesium, and this sodium titanate removed 99.9% of the strontium and 40.67% of cesium from an aqueous solution that had an initial concentration of 1.14 mM (100 mg L−1) strontium and 0.75 mM (100 mg L−1) cesium. Strontium adsorption by synthesized sodium titanate followed pseudo-second-order kinetics and a generalized Langmuir isotherm model, and reached an adsorption equilibrium within 1 h with high adsorption capacity at equilibrium. Adsorbed strontium onto synthesized sodium titanate showed the behavior of forming a strontium titanate structure with a titanate frame via surface precipitation.

Tuning the sumanene receptor structure towards the development of potentiometric sensors.

Herein, we report for the first time the application of a sumanene derivative in potentiometric recognition of caesium cations. The structure of the sumanene receptor was carefully tuned to obtain its compatibility with polyvinyl chloride plasticized membranes of potentiometric sensors. The developed ion-selective electrodes based on membranes doped with octyloxybenzene sumanene exhibited a near theoretical sensitivity towards caesium cations, with a detection limit of 4 μM Cs+.

3D Interaction of Zwitterions for Highly Stable and Efficient Inorganic CsPbI3 Solar Cells

AbstractAll‐inorganic cesium lead iodide (CsPbI3) perovskites, which replace volatile and hygroscopic organic components with stable inorganic cesium cations, have promising photoelectronic properties for potential application in solar cells. However, highly stable and efficient CsPbI3‐based perovskite solar cells are rarely reported because the optically active black phases of CsPbI3 tend to change into a photo‐inactive yellow δ‐phase. Herein, a highly stable CsPbI3 film that is formed by introducing a small quantity of zwitterions with different dimensions to the perovskite precursor solution is reported. The zwitterions effectively inhibit the formation of the yellow δ‐phase during perovskite crystallization and promote the development of a stable black α‐phase. In addition, a systematic analysis reveals strong interaction between 3D zwitterions and perovskites in both the solution and film states, which leads to a dense and pinhole‐free CsPbI3 film with suppressed trap states. The resulting perovskite solar cells with 3D zwitterions achieve a significantly improved power conversion efficiency of 18.4% with high reproducibility. The devices without encapsulation retain 98% of the initial efficiency after 25 days at 25 °C and relative humidity of 25% ± 5%. Importantly, the 3D zwitterion‐based devices demonstrate excellent phase stability when subjected to thermal aging at 100 °C.

A cost-effective water-in-salt electrolyte enables highly stable operation of a 2.15-V aqueous lithium-ion battery

Extensive efforts are currently underway to develop safe and cost-effective electrolytes for large-scale energy storage. In this regard, water-based electrolytes may be an attractive option, but their narrow electrochemical stability window hinders their realization. Although highly concentrated fluorinated electrolytes have been shown to be highly effective in suppression of water splitting, enabling significant widening of the applied potential range, they utilize expensive salts (e.g., lithium bis(trifluoromethane sulfonyl) imide [LiTFSI] or lithium trifluoromethane sulfonate [LiOTf]); hence, they cannot be considered for practical applications. Here, we demonstrate a cost-effective aqueous electrolyte solution combining 14 M LiCl and 4 M CsCl that allows stable operation of a 2.15-V battery comprising a TiO 2 anode and LiMn 2 O 4 cathode. Addition of CsCl to the electrolyte plays a double role in system stabilization: the added chloride anions interact with the free water molecules, whereas the chaotropic cesium cations adsorb at the electrified interface, preventing hydrogen formation. Mixed aqueous LiCl + CsCl electrolyte solution enables widely stable electrochemical window Cl − anions interact with the free H 2 O molecules and reduce their bulk activity The added chaotropic Cs + cations adsorb on the anode interface and prevent H 2 generation Long-term stable 2.15-V cell comprising TiO 2 anode and LiMn 2 O 4 cathode demonstrated The need for safe and cost-effective energy storage systems has advanced the development of aqueous batteries. Looking for a cost-effective electrolyte solution, Turgeman et al. propose saturated LiCl + 4 M CsCl. It is found that addition of CsCl significantly improves electrolyte stability and enables stable operation of a 2.15-V battery.

Deformation of polyiodides in Cs2I8 crystals at high pressure

Dicaesium octaiodide is composed of layers of zigzag polyiodide units (I8 2−) intercalated with caesium cations. Each I8 2− unit is built of two triiodides bridged with one diiodine molecules. This system was subjected to compression up to 5.9 GPa under hydrostatic conditions. Pressure alters the supramolecular architecture around I8 2−, leading to bending of the triiodide units away from their energetically preferred geometry (D ∞h). Short I2...I3 − contacts compress significantly, reaching lengths typical for the covalently bonded polyiodides. Unlike in reported structures at ambient conditions, pressure-induced catenation proceeds without symmetrization of the polyiodides, pointing to a different electron-transfer mechanism. The structure is shown to be half as compressible [B0 = 12.9 (4) GPa] than the similar CsI3 structure. The high bulk modulus is associated with higher I—I connectivity and a more compact cationic net, than in CsI3. The small discontinuity in the compressibility trend around 3 GPa suggests formation of more covalent I—I bonds. The potential sources of this discontinuity and its implication on the electronic properties of Cs2I8 are discussed.

Insight into the Role of Guanidinium and Cesium in Triple Cation Lead Halide Perovskites

The overall impact of the partial replacement (5–15%) of methylammonium (MA) in the MAPbI3 perovskite by cesium or guanidinium (Gua) cations to fabricate thin films of triple cation Cs x Gua y MA1–x–y PbI3 perovskites is studied. The structural changes are investigated by using X‐ray diffraction measurements revealing shrinkage or expansion of the unit cell upon Cs or Gua incorporation, respectively. The optoelectronic properties are characterized with photoluminescence (PL) time‐resolved spectroscopy and the space charge limited current (SCLC) method. Shorter PL time constants are obtained for the samples with only Cs, while longer PL decays are measured for the perovskites containing additional Gua cation. The SCLC measurements reveal a larger density of trap states in the Cs x MA1–x PbI3 perovskites compared to the MAPbI3 material. The PSCs fabricated with the different mixed cation Cs x Gua y MA1–x–y PbI3 perovskites reveal a good correlation with the measured optoelectronic properties. The power conversion efficiency (PCE) improves from an average value of 18.6% for the MAPbI3 to a value of 20.0% for the Cs0.05Gua0.05MA0.90PbI3 perovskite with a champion cell delivering 21.2%. On the opposite, the PCE decreases to a value of 17.3% for the double cation perovskite with Cs.

Polarizable cesium cations for energy storage from electrolyte characterization to-EDLC application

In the quest for new electrolytes on electrochemical energy storage devices, we present, characterize and test a simple organic electrolyte based on cesium bis (trifluoromethanesulfonyl) imide (CsTFSI) for supercapacitor (SC) application. The physicochemical properties of CsTFSI-based electrolytes in acetonitrile (ACN) and propylene carbonate (PC), alone and mixed with LiTFSI as a co-salt, were characterized under various concentrations and temperatures and revealed a different solution organization system, depending on the solvent and nature of the salt. The solvation radii based on the Jones-Dole-Kaminsky model indicated that ACN forms a single sphere of solvation around the cation Cs+, unlike PC, which does not solvate the large and polarizable Cs cation. The CsTFSI -ACN (1 mol L−1) electrolyte presents a suitable viscosity (<1 mPa•s) and density (36 mS cm−1) for SC application, ionic mobility within an extended temperature range (−40–60 °C), and its molecular level is compatible with the porosity of activated carbon (AC) electrodes. The nanopores of the ACs display good electronic conductivity and ion transport capability, characteristic of electrochemical double-layer capacitors EDLC within an electrochemical window of 3 V and a wide temperature span, i.e., −20–40 °C. In-situ measurements of accumulated gas pressure during typical galvanostatic charge-discharge protocols exposed a minimum pressure at 40 °C (2.6 × 108 Pa for CsTFSI-ACN, 1 mol L−1) compared to standard electrolytes (Et4BF4-ACN, 1 mol L−1) and yielded specific capacitances (Csp) of 115 F g−1 at a normalized current density of 2 A g−1. Standard accelerated aging floating tests confirmed the stability of the SCs (>100 h → 12% decrease on Csp). Finally, the suitability of CsTFSI as a co-salt (with lithium bis(trifluoromethanesulfonyl)imide, LiTFSI) was demonstrated for SC devices, aiming to boost Csp (i.e.,164 F g−1 for equimolar amounts of LiTFSI and CsTFSI). The above results attest to the functionality of CsTFSI as a promising salt for energy storage applications.

Electrochemical Sensing and Removal of Cesium from Water Using Prussian Blue Nanoparticle-Modified Screen-Printed Electrodes

Selective screening followed by the sensing of cesium radionuclides from contaminated water is a challenging technical issue. In this study, the adsorption functionality of Prussian blue (PB) nanoparticles was utilized for the detection and efficient removal of cesium cations. An efficient PB nanoparticle-modified screen-printed electrode (SPE) in the three-electrode configuration was developed for the electrochemical sensing and removal of Cs+. PB nanoparticles inks were obtained using a facile two-step process that was previously described as suitable for dispensing over freshly prepared screen-printed electrodes. The PB nanoparticle-modified SPE induced a cesium adsorption-dependent chronoamperometric signal based on ion exchange as a function of cesium concentration. This ion exchange, which is reversible and rapid, is associated with electron transfer in the PB nanoparticle-modified SPE. Using this electrochemical adsorption system (EAS) based on chronoamperometry, the maximum adsorption capacity (Qmax) of Cs+ ions in the PB nanoparticle-modified SPE reached up to 325 ± 1 mg·g−1 in a 50 ± 0.5 μM Cs+ solution, with a distribution coefficient (Kd) of 580 ± 5 L·g−1 for Cs+ removal. The cesium concentration-dependent adsorption of PB nanoparticles was also demonstrated by fluorescence spectroscopy based on fluorescence quenching of PB nanoparticles as a function of cesium concentration using a standard fluorophore like fluorescein in a manner analogous to that previously reported for As(III).