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Laser ablation in liquid (LAL) has emerged over the past decade as a powerful technique for the synthesis of nanomaterials and the fabrication of functional nanostructures. Its ability to tackle diverse challenges in nanotechnology highlights its growing significance. This review systematically evaluates recent advancements in LAL, focusing on the synthesis of nanocrystals and nanostructures. We begin by outlining the fundamental principles of the LAL process, with particular attention to critical laser parameters such as pulse wavelength, duration, pulse width, repetition rate, energy density (fluence) and the characteristics of the ablation medium. The review then explores the mechanisms that govern nanoparticle formation, with an emphasis on the control of particle shape and size during synthesis. Recent studies on LAL-generated nanomaterials, including bismuth oxide (Bi2O3), silver nanoparticles (Ag NPs) and germanium nanoparticles (Ge NPs), are discussed, highlighting their applications in ultraviolet photodetection. Key advantages of LAL, along with its limitations, are critically assessed, and potential strategies for overcoming these challenges are proposed. We conclude by identifying future research directions that will help advance the application of LAL in nanotechnology, particularly in the field of UV photodetectors. [ABSTRACT FROM AUTHOR]

The synthesis of germanium nanoparticles (Ge NPs) through pulsed laser ablation in deionized water is investigated for Nanophotonics and optoelectronic applications. This study delves into the influence of laser pulse energy on Ge NP properties, specifically highlighting size control and optical characteristics. Our findings reveal a significant reduction in Ge NP size, from an initial 30 nm to 20 nm, as the laser pulse energy increases. Notably, we observed size-dependent blue luminescence from the synthesized Ge NPs. This controlled synthesis holds promise for optoelectronics and sensing applications. The study provides valuable insights into precise Ge NP synthesis and underscores their intriguing optical properties, paving the way for advanced Nanophotonic devices.

Using the methods of nanosecond laser ablation in isopropyl alcohol and dry grinding of germanium, germanium nanoparticles were obtained for their possible application in liquid high-index immersion. Structural, chemical, and optical characterization of colloidal nanoparticles was carried out using scanning electron microscopy, IR spectroscopy, and energy-dispersive X-ray spectroscopy. [ABSTRACT FROM AUTHOR]

Physicochemical properties of stable nanoscale Ge particles have been widely investigated by means of radiation-chemical and chemical-reduction reactions of germanium ions in inversely micellar solutions, as well as various methods for registering the resulting nanoparticles, such as UV–Vis spectrophotometry (measurement of optical absorption and luminescence spectra) and AFM measurements. Depending on the concentration of components, the size of a water pool of inverse micelles, the storage time of samples, and the dose of ionizing radiation, the conditions for the formation of Ge NPs have been determined. Significant differences in the initial events of ion-reduction reactions have been revealed. The obtained results have confirmed the unique properties of polarized water in inverse-micellar solutions and the important role of the reducing properties of polarized water in various methods of the formation of Ge nanoparticles, including the processes of self-assembly and "molecular assembly" of metal and bimetal nanoparticles in the postreaction periods. [ABSTRACT FROM AUTHOR]

In this paper, we report the amorphous Ge NPs film which is fabricated at room-temperature by PECVD method. The uniform, compact and smooth film is formed by orderly packing of the Ge NPs in the longitudinal direction, resulting in the formation of columnar structures in the Ge NPs film. The electrical, optical properties and energy levels of the Ge NPs film meet the requirements of the OSCs for ETL, and the PTB7:PC 70 BM OSCs with the Ge NPs ETL shows the PCE of 7.38%. [Display omitted] • The amorphous Ge NPs film is fabricated by using the PECVD method at room temperature. • The compact and orderly packing of the NPs in the longitudinal direction leads to the formation of columnar structures in the Ge NPs film. • The electrical, optical properties and energy levels of the Ge NPs film meet the requirements of the OSCs for ETL. • The PTB7:PC 70 BM OSCs with the Ge NPs ETL shows the PCE of 7.38%. The performances of the organic solar cells (OSCs) largely depends on the selection and preparation of the electron transport layer (ETL). In this paper, the uniform and compact Ge nanoparticles (NPs) film was fabricated by using the plasma enhanced chemical vapor deposition (PECVD) method at room temperature. The Ge NPs film is formed by close packing of amorphous Ge particles with an average diameter of 6.05 nm, and the film shows a fairly smooth surface with a root-mean-square (RMS) roughness of 0.6419 nm. The results shows that Ge NPs film exhibits n-type characteristics, and the longitudinal conductivity of the film is 1.90 × 10−5 S/cm, which is better than that of the ZnO NPs film. The excellent longitudinal charge transport characteristics is attributed to the existence of the columnar structures in the Ge NPs. In addition, the Ge NPs film shows a visible light transmittance comparable to that of the ZnO NPs film. More importantly, the energy levels of the Ge NPs film meets the requirements of the PTB7:PC 70 BM OSCs for the ETL, and the devices with the Ge NPs ETL shows the power conversion efficiency (PCE) of 7.38%. The characteristic of room temperature preparation make the Ge NPs ETL may become a reliable choice for the flexible devices in the near future. [ABSTRACT FROM AUTHOR]

Abstract In recent years, germanium nanoparticles (Ge NPs) have attracted considerable research attention because of its excellent electrical and optical properties. However, it is mainly applied in the field of solar cells, photodetectors and photothermal therapy. Actually, Ge NPs have the advantages of low toxicity and excellent biocompatibility, which means that they have great potential in biosensing applications. However, there are few related reports. In this paper, we discovered that Ge NPs have the intrinsic peroxidase-like catalytic activity and can significantly accelerate the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H 2 O 2 for the first time. Compared with natural enzyme (horseradish peroxidase, HRP), Ge NPs maintain higher catalytic stability after treatment at different pH, temperature and ionic strength. Furthermore, a Ge NPs-based colorimetric platform was established for the first time to detect biomolecules with favourable sensitivity and selectivity, such as uric acid, glucose and choline. This work finds the new property of Ge NPs and extends its application in biosensing. Graphical abstract fx1 Highlights • The intrinsic peroxidase-like catalytic activity of germanium nanoparticles (Ge NPs) was testified for the first time. • Ge NPs exhibited excellent activity in resisting pH and temperature change than natural enzymes. • A Ge NPs-based colorimetric platform was built for biomolecules detection with favourable sensitivity and selectivity. • This is also the discovery of the new property of Ge NPs and the extension of its applications. [ABSTRACT FROM AUTHOR]

In the present work, circular Metal-Oxide-Semiconductor capacitors with 200 μm of diameter and germanium (Ge) nanoparticles (NPs) embedded in the gate oxide are studied for memory applications. Optimal process parameters are investigated for Ge NPs growing by low pressure chemical vapor deposition at different deposition times. Photoluminescence measurements showed room-temperature size-dependent green-red region bands attributed to quantum confinement effects present in the NPs. High-frequency capacitance versus voltage measurements demonstrated the memory effects on the MOS structures due to the presence of Ge NPs in the gate oxide acting as discrete floating gates. Current versus voltage measurements confirmed the Fowler-Nordheim tunneling as the programming mechanism of the devices. [ABSTRACT FROM AUTHOR]

Germanium (Ge) nanoparticles (NPs) are synthesized by means of pulsed laser ablation of bulk germanium target immersed in acetone with ns laser pulses at different pulse energies. The fabricated NPs are characterized by employing different techniques such as UV-visible absorption spectroscopy, photoluminescence, micro-Raman spectroscopy, transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). The mean size of the Ge NPs is found to vary from few nm to 40 nm with the increase in laser pulse energy. Shift in the position of the absorption spectra is observed and also the photoluminescence peak shift is observed due to quantum confinement effects. High resolution TEM combined with micro-Raman spectroscopy confirms the crystalline nature of the generated germanium nanoparticles. The formation of various sizes of germanium NPs at different laser pulse energies is evident from the asymmetry in the Raman spectra and the shift in its peak position towards the lower wavenumber side. The FESEM micrographs confirm the formation of germanium micro/nanostructures at the laser ablated position of the bulk germanium. In particular, the measured NP sizes from the micro-Raman phonon quantum confinement model are found in good agreement with TEM measurements of Ge NPs.

Abstract: Controlled synthesis of carbon nanotubes (CNTs) is highly desirable for nanoelectronic applications. To date, metallic catalyst particles have been deemed unavoidable for the nucleation and growth of any kind of CNTs. Ordered arrays of nanotubes have been obtained by controlled deposition of the metallic catalyst particles. However, the presence of metal species mixed with the CNTs represents a shortcoming for most electronic applications, as metal particles are incompatible with silicon semiconductor technology. In the present paper we report on a metal-catalyst-free synthesis of CNTs, obtained through Ge nanoparticles on a Si(001) surface patterned by nanoindentation. By using acetylene as the carbon feed gas in a low-pressure Chemical Vapor Deposition (CVD) system, multi-walled carbon nanotubes (MWNT) have been observed to arise from the smallest Ge islands. The CNTs and the Ge three-dimensional structures have been analysed by SEM, EDX and AFM in order to assess their elemental features and properties. EDX and SEM results allow confirmation of the absence of any metallic contamination on the surface, indicating that the origin of the CNT growth is due to the Ge nanocrystals. [Copyright &y& Elsevier]

Germanium is a promising active material for high energy density anodes in Li-ion batteries thanks to its good Li-ion conduction and mechanical properties. However, a deep understanding of the (de)lithiation mechanism of Ge requires advanced characterizations to correlate structural and chemical evolution during charge and discharge. Here we report a combined operando X-ray diffraction (XRD) and ex situ Li solid-state NMR investigation performed on crystalline germanium nanoparticles (c-Ge Nps) based anodes during partial and complete cycling at C/10 7 Li solid-state NMR investigation performed on crystalline germanium nanoparticles (c-Ge Nps) based anodes during partial and complete cycling at C/10 versus Li metal. High-resolution XRD data, acquired along three successive partial cycles, revealed the formation process of crystalline core-amorphous shell particles and their associated strain behavior, demonstrating the reversibility of the c-Ge lattice strain, unlike what is observed in the crystalline silicon nanoparticles. Moreover, the crystalline and amorphous lithiated phases formed during a complete lithiation cycle are identified. Amorphous Li 7 Ge 3 and Li 7 Ge 2 are formed successively, followed by the appearance of crystalline Li 15 Ge 4 (c-Li 15 Ge 4 ) at the end of lithiation. These results highlight the enhanced mechanical properties of germanium compared to silicon, which can mitigate pulverization and increase structural stability, in the perspective for developing high-performance anodes.

• The GeGrNPs material shows a porous structure. • The anode architecture of GeGrNPs is unique and superior to conventional structure. • The GeGrNPs electrode exhibits outstanding electrochemical performance. First-principles calculations forecast that germanium incorporated graphite has potential to be used as high performance negative electrode for lithium-ion batteries due to large mobility of electrons at the heterointerface. Inspired by this first-principles calculations, a novel functional structure of thin graphite nanoplatelets embedding a finely dispersed germanium component is fabricated through a scalable ball milling technique for the first time. Nitrogen adsorption-desorption isotherms and electron microscopy investigation demonstrate that the obtained electrode materials exhibit mesoporous features where germanium nanoparticles are implanted into the graphitic matrix of thin flakes. Such a novel structure provides several advantages including large surface area, high accessibility of lithium ions and shortened lithium ion diffusion distances, which enable fast ion and electron transfer at the interface of electrolyte and electrode. As results, the obtained electrode demonstrates promising electrochemical performance with a charge capacity of 822 mAh g−1 after 200 cycles at 0.1 C, high rate capacity of 325 mAh g−1 at 10 C and good cyclic stability with a capacity retention of 97%. This work delivers a robust electrode design strategy as well as the most practical route for the improvement of germanium-based anodes for application in lithium-ion batteries. [ABSTRACT FROM AUTHOR]

We demonstrate solar steam generation with high evaporation rates and extraction of dry salts from solutions by using water-repellent germanium nanoparticles (GeNPs)-coated oxidized copper foams (CFs) as light absorbers and heat concentrators. The CF surface was first oxidized into black CuO, then dip-coated with colloidal GeNPs for enhancing infrared absorption, and lastly treated with perfluoroalkyl silane to render hydrophobicity. The CF can absorb more than 95% of the AM1.5G solar irradiance spectrum, for heating up a water-permeated cellulose paper underneath to generate steam which is then evacuated through the CF's interconnected pores. Furthermore, due to the CF's high thermal conductivity, the heat generated in the peripheral region can be efficiently concentrated to the center where the water evaporates. With the light-absorbing CF area about 7 times larger than the water-evaporating cellulose paper and the convective heat loss mitigated by an acrylic cover, under one sun solar irradiance, the CF temperature can reach 70 °C, resulting in an evaporation rate as high as 3.2 kg m−2 h−1. Moreover, when a NaCl solution is used for the heat-concentrating evaporation inside an enclosed system in which the water condensate is recycled, readily useful dry salts are formed and can be harvested from the hydrophobic CF surface, while the bulk solution is gradually desalinized. • While being clean and inexhaustible, one major issue of solar energy is its relatively low energy density. As a result, for solar steam generation, optical concentration is often employed to increase the evaporation rate. However, the optical concentrating systems are usually quite expensive. • We demonstrate heat-concentrating solar steam generation with high vapor temperature (70 °C) and high evaporation rate (3.2 kg m−2 h−1) by using water-repellent germanium nanoparticles (GeNPs)-coated oxidized copper foams (CFs) as light absorbers and heat concentrators. • The CF surface was first oxidized into black CuO, then dip-coated with colloidal GeNPs for enhancing infrared absorption, and lastly treated with perfluoroalkyl silane to render hydrophobicity. The CF can absorb more than 95% of the AM1.5G solar irradiance spectrum. • The major byproduct from coastal seawater desalination is the highly concentrated solution of salts. Traditionally, electrodialysis is used to extract salts from the brine, which however has high energy demands and requires the pre-treatment of feedwater. • As a green alternative to the electrodialysis method, we demonstrate the extraction of dry salts from NaCl solutions by using the water-repellent GeNPs-coated oxidized CFs. [ABSTRACT FROM AUTHOR]

The light reflection spectra of Ge disk nanoresonators on a Si substrate are studied, depending on their diameter (d) and height (h). The Ge disks, fabricated at temperatures close to room temperature using the bottom-up approach, exhibit a polycrystalline structure. The reflection at resonance wavelengths decreases more than 10 times, compared to surface areas without disks when the disk aspect ratio h/d increases to 1.0 and d > 100 nm. The strong dependence of the reflection minimum on h/d can be associated with the influence of the substrate. An effective refractive index, defined as n eff = λ m / d and determining the long-wavelength resonance mode position λ m , turns out to be larger for disks than for spheres. It is also significantly larger than the Ge refractive index. This allows the use of disks of smaller diameter than spheres to achieve the resonance effects at the same wavelength. • Arrays of germanium nanodisks were fabricated using bottom-up approach. • Sample reflectance was measured for disks with different height (h) and diameter (d). • Well-pronounced resonance effects are observed for disks with h > 100 nm. • Reflection at resonance wavelengths decreases more than 10 times when h / d ~ 1.0 • Refractive index of Ge is significantly smaller than that determined as n eff = λ m / d. [ABSTRACT FROM AUTHOR]

We report the spark discharge synthesis of aerosol germanium nanoparticles followed by sintering in a tube furnace at different temperatures varying from 25 to 800 °C. The size, structure, chemical composition and optical properties were studied. We have demonstrated a melting mechanism of nanoparticles agglomerates, the growth of the mean primary particle size from 7 to 51 nm and the reduction of the size of agglomerates with a temperature increase. According to transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) data, primary nanoparticles sintered at temperatures from 25 to 475 °C basically have a structure of Ge crystals embedded in a GeOx amorphous matrix, as well as visible photoluminescence (PL) with the maximum at 550 nm. Pure germanium nanoparticles are prepared at temperatures above 625 °C and distinguished by their absence of visible PL. The shape of the experimental UV-vis-NIR extinction spectra significantly depends on the size distribution of the germanium crystals. This fact was confirmed by simulations according to Mie theory for obtained ensembles of germanium nanoparticles. [ABSTRACT FROM AUTHOR]

Herein we report the electroless deposition of Ge onto sacrificial Ag nanoparticle (NP) templates to form hollow Ge NPs. The formation of AgI is a necessary component for this reaction. Through a systematic study of surface passivating ligands, we determined that tri-n-octylphosphine is necessary to facilitate the formation of hollow Ge NPs by acting as a transport agent for GeI2 and the oxidized Ag(+) cation (i.e., AgI product). Annular dark-field (ADF) scanning transmission electron microscopy (STEM) imaging of incomplete reactions revealed Ag/Ge core/shell NPs; in contrast, completed reactions displayed hollow Ge NPs with pinholes which is consistent with the known method for dissolution of the nanotemplate. Characterization of the hollow Ge NPs was performed by transmission electron microscopy, ADF-STEM, energy-dispersive X-ray spectroscopy, UV-vis spectrophotometry, and Raman spectroscopy. The galvanic replacement reaction of Ag with GeI2 offers a versatile method for controlling the structure of Ge nanomaterials.