A review of synthetic methods for the production of upconverting lanthanide nanoparticles

Abstract

Upconverting lanthanide nanoparticles overcome many of the problems associated with more traditionally used luminescent contrast agents, such as photobleaching, auto°uorescence, cytotoxicity and phototoxicity. For this reason, they are an attractive choice for biomedical imaging applications, particularly for imaging in living tissues. The last decade has seen numerous improvements to these nanocrystals, but a comprehensive guide to the synthesis of upconverting lanthanide nanoparticles has not yet been written. Methods vary from paper to paper and from group to group, and results vary between research groups for each method. For this reason, development of these nanoparticles remains a signi¯cant endeavor for any research group interested in joining the¯eld. In this review, we look at the varying synthetic methods employed over the last decade and detail methodology for a select few that have been favored in the¯eld.

Labeling of HeLa cells using ZrO 2 : Yb 3 + - Er 3 + nanoparticles with upconversion emission

“…[3][4][5][6] Other advantages of the UPC emission are the reduction of photobleaching and scattering in tissues, which avoid the use of complicated and high-cost femtosecond lasers and photomultiplier tubes. [7][8][9][10] For biomedical applications, such as cancer detection, biolabeling, and bioimaging, luminescent nanoparticles preferably have to form a stable colloidal solution under physiological conditions. However, common nanomaterials with strong UPC emission, such as Yb 3þ -Er 3þ co-doped Y 2 O 2 S, Yb 3þ -Ho 3þ codoped Y 2 O 3 , and Yb 3þ -Er 3þ -Tm 3þ doped NaYF 4 , are hydrophobic.…”

Recent Advancements in Ln‐Ion‐Based Upconverting Nanomaterials and Their Biological Applications

“…Recently, tremendous attention has been paid on the synthesis and spectroscopic analysis of RE ion‐doped UCNPs with controlled shapes, sizes, and crystalline phases . A variety of synthetic methods have been identified that include coprecipitation, hydrothermal/solvothermal process, seed‐mediated heat‐up approach, decomposition of mixed trifluoroacetates, template method, sol–gel method, and Ostwald‐ripening epitaxial shell growth, which have been reviewed in many papers as well . These methods are the most widely used methods for the synthesis of UCNPs because they offer precise control over phases, sizes, and morphologies of UCNPs.…”

“…[56][57][58][59][60][61] A variety of synthetic methods have been identified that include coprecipitation, [62] hydrothermal/solvothermal process, [63] seedmediated heat-up approach, [64] decomposition of mixed trifluoroacetates, [51,56,[65][66][67][68][69] template method, [70] sol-gel method, [71] and Ostwald-ripening epitaxial shell growth, [72] which have been reviewed in many papers as well. [36,53,[73][74][75][76][77][78] These methods are the most widely used methods for the synthesis of UCNPs because they offer precise control over phases, sizes, and morphologies of UCNPs. This section of the review also focuses particularly on the details about these synthetic methods for UCNPs.…”

Au-nanocluster-loaded human serum albumin nanoparticles with enhanced cellular uptake for fluorescent imaging

“…Most of these approaches consist in mildly reducing Au ions in the presence of thiolcontaining stabilizers. The use of serum proteins, e.g., bovine serum albumin (BSA) and human serum albumin (HSA), as biocompatible reducing and stabilizing agents gives rise to AuNCs with strong red emission and a decent QY, 13,14 comparable to that of upconverting 15 or dye-doped 16 nanoparticles. Owing to their easy synthesis, biocompatibility, and excellent°uorescent properties, AuNCs have been useful in various applications, including sensing [17][18][19] and bioimaging in vitro and in vivo.…”